Exam 1 Review (Lectures 1-7)
Age of the Earth: ~4.54 billion years
Contour line: Seen on topographic maps; close lines indicate steep slopes while further apart lines are lines of equal elevation.
Cross-section: A diagram that shows how different geological features are layered; may include rock types, folds, faults, dikes, and water passages.
Deep time: Immense amounts of time.
Evolution: A unifying theory for understanding history of life. It is the way that living systems move through time. Fossil records help show changes through time.
Hypothesis: A suggested idea put forward for consideration; it aligns with all current data and is likely to explain future observations. It is a limited explanation of the phenomenon.
Law: A concise statement of what will happen, but does not explain how or why they work.
Plate tectonics: The large-scale deformation of rocks in Earth's outer layers, serving as a comprehensive theory that explains many geological phenomena.
Science: Uses observations, experiments, and calculations to explain how things work, involving critical thinking through systematic steps that analyze scientific problems and yield verifiable results.
Scientific method: A systematic process used to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge. It typically involves making observations, forming a hypothesis, conducting experiments, analyzing the results, and drawing conclusions to test and refine the original hypothesis.
Theory: A hypothesis that has not yet been proven wrong; abundance of evidence. Explains how and/or why things happen; can be used to make predictions. Arises from tested hypotheses.
Topographic map: A detailed and accurate representation of natural and man-made features on the Earth's surface. It uses contour lines to show the elevation and shape of the terrain, providing information on the landscape's physical characteristics.
What is a topographic map? What is a contour line?
A topographic map displays detailed terrain features, including elevation, using contour lines to connect points of equal height.
Contour lines help visualize landforms and slopes, with their spacing indicating the steepness of the terrain.
What are cross-sections? How do you read a geologic map or cross-section?
Cross-sections are vertical views of the Earth's layers, showing their arrangement.
To read a geologic map, identify rock types and structures by their colors and symbols, then use cross-sections to see how these features change in depth and how they are arranged below the surface.
What is the scientific method? What is a hypothesis, a theory, a law, and what are the differences?
Scientific Method: A process of observation, hypothesis formation, experimentation, and analysis to gain knowledge.
Hypothesis: A testable, educated guess about a phenomenon.
Theory: A well-supported explanation of natural phenomena, based on evidence and tested hypotheses.
Law: A statement that describes a consistent natural pattern or relationship, often mathematically, without explaining why it occurs.
Differences:
Hypothesis: Specific and testable.
Theory: Broad, explanatory, and evidence-based.
Law: Describes what happens, often mathematically, without explanation.
Actualism: The natural laws and processes we observe today have always operated throughout Earth's history. Unlike uniformitarianism, it recognizes that the rates and intensities of these processes can vary over time, applying current natural laws to past events without assuming constant rates.
Australopithecus: Tracks found by Mary Leakey resolved an issue of early humankind. Did walking upright lead to brain development OR brain development lead to walking upright.
Charles Lyell: Formalized uniformitarianism, stressing consistent natural processes over time. He noted geological features cutting across rock are younger and emphasized relative dating.
East African Rift Valley: Continent is splitting apart and the wet volcanic ash preserves the footprints of elephants, three toed horses, saber-toothed cats, insects, and millipedes. Additionally, footprints of two Australopithecus afarensis individuals (the same species as the Lucy fossil) have been preserved.
Eons: The largest divisions of geological time, spanning billions of years.
Eras: Subdivisions of eons, each lasting hundreds of millions of years
James Hutton: The father of geology; best known for his theory of uniformitarianism and for proposing the concept of deep geological time.
Krakatoa: Volcanic eruption that occurred on a convergent plate boundary (where ocean crust collided with continental crust).
Mount Vesuvius: The volcanic eruption resulted from the convergence of the African and Eurasian plates. It buried the city of Pompeii under a combination of earthquakes, gases, ash, and mudflows.
Neptunism: The geological theory that all rocks originated from sedimented deposits of minerals in the Earth’s oceans.
Nicholas Steno: Father of stratigraphy (strata meaning layers); Recognized that rock layers were not all formed simultaneously and that variations in conditions resulted in different types of rocks. He also proposed that fossils were formed during the same time as the surrounding rocks.
Periods: Subdivisions of eras, typically lasting tens of millions of years.
Plutonism: The geological theory that rocks, especially igneous rocks, form from the cooling and solidification of molten magma beneath the Earth's surface.
Santorini Island: Catastrophic volcanic eruption that occurred during the Africa and Eurasian plate convergence. It was three to four rimes the magnitude of Krakatoa and likely ended the Minoan civilization.
Siccar Point: Outcrop and unconformity; deduced that all we see on this planet could be explained by these processes and time
Uniformitarianism: The principle that the same natural laws and processes that operate in the universe now have always operated in the past. It suggests that geological processes observed today can be used to interpret past geological events. This concept emphasizes consistency over time.
William Smith: Created first geologic map based largely in part on fossils.
What is uniformitarianism? Why is this important for understanding historical geology? What are some examples?
Uniformitarianism: The principle that the geological processes we observe today, like erosion and sedimentation, have been occurring in the same manner throughout Earth's history.
Importance: Allows geologists to use present-day observations to interpret and understand the Earth's geological past. Provides a consistent framework for studying and reconstructing the history of Earth’s surface and processes over long periods.
Examples: Erosion, sedimentation, volcanic activity, plate tectonics.
Who were some of the people that contributed to improving the science behind historical geology? What did they contribute?
Abraham Gottlob Werner - Developed the Neptunist theory, suggesting that rocks formed from crystallization in the early Earth's oceans, influencing early geological thought.
James Hutton - Introduced the concept of deep time and uniformitarianism, proposing that Earth's features were shaped by continuous and gradual processes over immense periods.
Charles Lyell - Popularized uniformitarianism, emphasizing that the same geological processes observed today have been shaping Earth throughout its history.
Nicholas Steno - Formulated foundational principles of stratigraphy, such as the law of superposition, which helped to understand the chronological order of rock layers.
William Smith - Created the first geological map and established the principle of faunal succession, using fossils to correlate rock layers and understand their relative ages.
What are the names and approximate ages of the Eons, Eras, and Periods?
What are examples of dramatic geologic events in the recent geologic past? What were some of the basics of those events (e.g., type of plate boundary)?
Krakatoa, Mt. Vesuvius, Santorini, East African Rift Valley, Australopithecus Tracks
Absolute age dating: Provides a precise age for rocks or fossils, giving a specific number of years since they were formed. This helps to create an accurate timeline of geological and archaeological events.
Angular conformity: Two layers of rock meet that are inclined or tilted at different angles to one another. The angled layers are beneath the new rock.
Correlation: The process of matching rocks found in different places (of equivalent age).
Cross-cutting relationships: Geologic features such as faults and dikes that cut through rock layers are younger than the rocks they intersect. These features indicate the most recent events when they are present.
Dike: A vertical or steeply inclined sheet of igneous rock that forms when magma forces its way through and solidifies across existing rock layers.
Disconformity: A gap between two sedimentary layers that are parallel; erosion, but no tilting.
Fault: A fracture or zone of fractures in the Earth's crust along which there has been movement and displacement of the rock on either side. Faults are caused by tectonic forces and can vary in size.
Faunal succession: Different organisms' fossils first appear at different times in the rock record. Related organisms' fossils show regular changes in progressively younger rocks wherever they are found. Once organisms become extinct, their fossils disappear from the rock record simultaneously and do not reappear in younger rocks.
Fossil: The preserved remains or traces of a living thing from long ago.
Inclusions: Objects enclosed in rock must be older than the rock itself. The objects must have existed before being embedded in the newer rock formation.
Index fossil: Fossils used to define and identify geologic periods; considered units of study in biostratigraphy. The fossils must be wide spread, fast evolving, common, easily preserved, and easily identified.
Lateral continuity: Rock layers initially extend laterally in all directions until they thin out or reach a physical barrier. This suggests that rock layers that are now separated by a valley or other erosional features were once continuous.
Nonconformity: Where sedimentary or volcanic rocks lie directly on igneous or metamorphic rocks.
Original horizontality: A tectonic force tilts the sedimentary layers up. Using superposition, we know the bottom rock is the oldest, the top rock is the youngest, and the most recent event is the tectonic tilt.
Relative age dating: Involves examining rocks in the field to determine the sequence of events that created them. It establishes the order of events without specifying the exact time they occurred.
Sequence: Order of events.
Stratigraphy: The branch of geology that studies rock layers (strata) and layering (stratification).
Sequence stratigraphy: Based on changes in global sea levels over time.
Superposition: Rock on the top is younger, rock on the bottom is older.
Unconformity: An erosional gap in the geological record within rock layers, representing a period of erosion or non-deposition.
What is relative age dating?
A method used to determine if one rock or fossil is older or younger than another without knowing their exact ages. This is done by looking at the positions of rock layers and the fossils within them.
What are the relative age dating principles and how are they used?
Superposition - Determine the relative ages of sedimentary rock layers.
Original Horizontality - If rock layers are found tilted or folded, it indicates that they have been disturbed after their initial deposition.
Cross-Cutting Relationships - Used to determine the relative ages of the features by observing which ones cut across others.
Inclusions - Used to determine that the rock containing the fragments is younger than the fragments themselves.
Lateral Continuity - Used to match rock layers that have been separated by erosion or other geological events.
Faunal Succession - Use fossils within rock layers to correlate the ages of rocks from different locations.
What is sequence stratigraphy?
A method of studying sedimentary rock layers (strata) and their temporal and spatial relationships to understand the geological history of sediment deposition and sea level changes.
What is an unconformity and what are the different types?
A surface in the rock record that represents a period of erosion or non-deposition, indicating a gap in the geological history. Types are angular, disconformity, and nonconformity.
How do we use the relative age dating principles in chronologically ordering layers in a cross-section?
Examine the cross-section to identify the various rock layers and their relationships.
Order the layers from oldest at the bottom to youngest at the top.
Confirm that any layers that are not horizontal have been altered after deposition. Adjust the order if necessary to reflect the original sequence.
Determine the relative ages of features such as faults or intrusions. The features cutting through other layers are younger than the layers they disrupt.
Identify any rock fragments (inclusions) within the layers. The layer containing the inclusions is younger than the fragments.
Use fossils within the layers to correlate and date the layers, ensuring that the fossil content is consistent with the known sequence of fossil appearance and extinction.
Absolute age dating: A method used to determine the exact age of a rock, fossil, or other object in years. This is achieved through techniques such as radiometric dating.
Acasta Gneiss: The oldest intact rock on Earth; type of metamorphic rock. Age is ~4.0 Ga
Daughter isotope: The new isotope.
Half-life: The amount of time it takes for ½ of parent isotopes to decay to daughter
Henri Becquerel: Discovered radioactivity in 1896.
Isotopes: Versions of elements that have different numbers of neutrons and, as a result, different atomic weights.
Lord Kelvin: Published the first of several heat-flow calculations for cooling Earth. Used laws of heat convection and radiation to estimate Earth’s age, it was older than he predicted.
Marie Curie: Discovered the elements radium and polonium were radioactive while investigating the radioactivity of the mineral pitchblende (uraninite); coined “Radioactivity” as a term denoting emissions in Radium. 1st woman to win Nobel Prize.
Parent isotope: The original, radioactive isotope.
Radioactive decay: Measures the decay of radioactive isotopes within the material to calculate how long it has been since the object was formed; provides the basis for modern isotopic dating.
Radioactivity: The spontaneous emission of particles or energy from the unstable nucleus of an atom as it transforms into a more stable form; produces heat.
Radiocarbon dating: A technique used to find out how old something is by measuring the amount of carbon-14 it contains. This method is useful for dating materials that were once alive
Radiometric dating: A method used to determine the age or history of an object, i.e. the Earth, by measuring the amount of certain radioactive elements it contains and how they decay over time.
Relative age dating: Determines the age of a rock or fossil in comparison to other objects; doesn't provide an exact age, tells us whether something is older or younger than something else. Done by looking at position of rock layers and fossils (superposition).
Zircon: Minerals that contain zirconium and can be used to date rocks because they preserve age information from uranium decay over billions of years.
What is absolute age dating and how do we determine absolute ages?
Absolute age dating is a method used to determine the exact age of a rock, fossil, or other object in years.
Radiometric dating measures the decay of radioactive isotopes within the material.
What are parent and daughter isotopes? What is a half-life?
Parent isotope - the original, radioactive isotopes.
Daughter isotope - the new isotope.
Half-life - amount of time it takes for ½ of parent isotopes to decay to daughter.
What geologic events can we date?
We can date events like volcanic eruptions, sediment formation, metamorphic changes, faulting, erosion, and fossilization using various dating methods.
How do we know absolute dating works?
Ages confirmed by historical observations.
Ages agree with superposition.
Ages on one rock determined by multiple dating methods in different labs agree.
Ages are consistent with known geologic or solar system history.
How would we date sedimentary rocks?
Radiometric Dating: Date minerals within the sedimentary rock, such as zircon, to determine the age of the rock formation.
Fossils: Use fossils within the rock to correlate with known ages from other locations.
Stratigraphy: Apply principles like the Law of Superposition to compare the relative ages of sedimentary layers.
Andesite: Igneous, type of volcanic rock that is gray to dark gray in color and forms from lava that is intermediate in composition between basalt and rhyolite.
Aphanitic: Type of texture that contains small, fine grained crystals due to fast cooling; usually extrusive, but not always. Examples: rhyolite, andesite, basalt
Assimilation: When molten rock (magma) melts and incorporates surrounding rock, changing the magma's composition.
Basalt: Igneous, a dark-colored, fine-grained volcanic rock that forms from the rapid cooling of low-viscosity lava rich in iron and magnesium.
Carbonate: Sedimentary; chemically or biologically precipitated, marine.
Chalk: Sedimentary, a soft, white, fine-grained sedimentary rock composed mainly of the mineral calcite, which forms from the accumulation of tiny marine organisms' shells and skeletons.
Chert: Sedimentary, a hard, fine-grained sedimentary rock made mostly of silica, often formed from marine organisms' remains or silica precipitation.
Clastic: Composed of mineral grains weathered from pre-existing rock and cemented together by precipitated minerals. Gravel → Sand → Silt → Clay
Cleavage: The tendency of a mineral to break along specific planes of weakness, resulting in smooth, flat surfaces; how minerals split.
Coal: Sedimentary; made of plant matter.
Crystal habit: The characteristic shape and form of a mineral crystal, including its overall growth pattern and the arrangement of its faces.
Decompression: The reduction of pressure or stress on magma, allowing it to rise and potentially solidify as it moves towards the Earth's surface.
Deposition: When materials like sand, silt, or gravel settle out of water or wind and build up in new locations.
Evaporite: Minerals that form from the evaporation of water, leaving behind solid deposits like salt or gypsum.
Extrusive: Type of igneous rocks that form from the rapid cooling and solidification of lava on Earth's surface; volcanic rocks, crystals are not present.
Felsic: A type of igneous rock that are light in color and rich in silica and aluminum, containing minerals such as quartz and feldspar. They typically form from magma that cools slowly underground. More silica, high viscosity.
Foliated: A planar alignment of metamorphic minerals (especially micas) with mineral alignment perpendicular to highest stress direction; differential pressure (or stress) is applied.
Fractional crystallization: A process where different minerals crystallize from molten rock (magma) at different temperatures, causing the composition of the remaining magma to change over time.
Frothy: A rock with this texture has a bubbly or spongy appearance, often due to trapped gas bubbles in the volcanic glass or lava that cooled quickly.
Gabbro: Igneous, a dark, coarse-grained rock with a phaneritic texture that forms from the slow cooling of magma beneath the Earth's surface, composed mainly of minerals like plagioclase and pyroxene.
Glassy: Texture in minerals that occurs when molten lava cools so quickly that crystals do not have time to form. Example: obsidian
Gneiss: Metamorphic, a high-grade rock characterized by its layered or banded appearance, formed from the alteration of granite or other rocks under high pressure and temperature.
Granite: Igneous rock
Halite: A mineral commonly known as rock salt, composed of sodium chloride (NaCl), and often forms from the evaporation of seawater.
Hardness: A measure of how resistant a mineral is to scratching or abrasion.
Heat transfer: The movement of thermal energy within the Earth, occurring through conduction, convection, or radiation.
Igneous rock: Forms from the cooling and solidification of molten a melt (magma or lava).
Intermediate: An igneous rock with a composition between that of basalt and granite, containing moderate amounts of silica and a mix of light and dark minerals.
Intrusive:
Lava: Melt above Earth’s surface.
Limestone: Sedimentary rock primarily composed of calcium carbonate, often formed from the remains of marine organisms like coral and shells.
Luster: The way a mineral reflects light from its surface. It describes the quality and appearance of the shine, which can be categorized as metallic, vitreous (glass-like), pearly, silky, or dull.
Mafic: Dark-colored igneous rocks that are rich in iron and magnesium, with minerals like pyroxene and olivine. Less silica, low viscosity.
Magma: Melt below Earth’s surface.
Magmatic differentiation: Process by which different rocks form from a single magma.
Metamorphic grade: Change of texture and mineral; progressive change in which minerals grow as a function of pressure and temperature. Low grade = can’t see minerals, intermediate grade = can see minerals, high grade = banded minerals.
Metamorphic rock: Formed from the alteration of existing rocks (igneous, sedimentary, or other metamorphic rocks) through heat, pressure, and chemical processes, resulting in new mineralogical and structural features.
Mineral: A naturally occurring, inorganic solid with a specific chemical composition and a crystalline structure.
Non-foliated: Metamorphic rocks that lack a layered or banded appearance, with minerals that are recrystallized without a preferred orientation; uniform pressure (or stress) is applied.
Partial melting: The process where only a portion of a rock melts to form magma, while the rest remains solid.
Pegmatitic: A texture in igneous rocks where the mineral crystals are exceptionally large and coarse-grained, often forming in the final stages of magma crystallization.
Phaneritic: A texture in intrusive igneous rocks where the mineral crystals are large enough to be seen with the naked eye, indicating that the rock cooled slowly beneath the Earth's surface.
Phyllite: A type of metamorphic rock that is intermediate between slate and schist, characterized by a shiny, slightly wavy surface and fine-grained texture.
Plutonic rocks: Type of igneous rock; slow cooling and solidification of magma beneath Earth's surface, intrusive.
Porphyritic: A texture in igneous rocks where large crystals, called phenocrysts, are embedded in a finer-grained or glassy groundmass.
Protolith: Pre-existing rock of new metamorphic rock.
Rock cycle: A continuous process where rocks are transformed between igneous, sedimentary, and metamorphic forms through geological processes like melting, erosion, and pressure changes.
Rhyolite: Igneous rock; light-colored, fine-grained volcanic rock that is high in silica and typically contains minerals like quartz and feldspar.
Sedimentary rock: Formed from the accumulation, compaction, and cementation of sediments, which can include fragments of other rocks, minerals, and organic materials.
Schist: A type of metamorphic rock characterized by its foliated texture, with visible layers or bands of minerals like mica, quartz, and garnet, formed under high pressure and temperature conditions.
Silicates: The dominate class. Minerals that contain silicon and oxygen, typically combined with other elements like aluminum, iron, magnesium, or potassium. They are the most common group of minerals in Earth's crust, including minerals like quartz, feldspar, and mica.
Slate: A fine-grained metamorphic rock that forms from the metamorphism of shale, characterized by its ability to break into thin, flat layers.
Solid-state change: The transformation of a rock's mineral composition and structure without melting, through processes like heat and pressure, which leads to the formation of new minerals and textures.
Streak: The color of a mineral's powder when it is scraped across a porcelain plate or streak plate
Ultramafic: Igneous rocks that are very low in silica and high in iron and magnesium, often containing minerals like olivine and pyroxene.
Vesicular: A texture in volcanic rocks characterized by numerous gas bubbles or vesicles trapped within the rock, giving it a porous appearance.
Viscosity: Resistance to flow; depends on temperature, volatile content, and silica content.
Volatiles: Substances that easily evaporate or turn into gas at relatively low temperatures.
Volcanic rock: Type of igneous rock, forms from the rapid cooling and solidification of lava on the Earth's surface, extrusive.
What are minerals? What are the physical properties used to identify them?
Minerals: Naturally occurring, inorganic solid substances with a definite chemical composition and crystalline structure.
Physical properties used to identify minerals: Hardness, color, streak, luster, cleavage, fracture, and specific gravity.
What are the dominant elements in our crust? What is the dominant class of minerals?
Dominant elements in our crust: Oxygen and silicon.
Dominant class of minerals: Silicates.
What are the major rock groups and how do they form? How are they classified? How do we use composition and texture to classify each rock type?
Major rock groups and their formation:
Igneous rocks: Formed from the cooling and solidification of magma or lava.
Sedimentary rocks: Formed from the accumulation, compaction, and cementation of sediments.
Metamorphic rocks: Formed from the alteration of existing rocks through heat, pressure, or chemically active fluids.
Classification:
Igneous rocks: Classified by their mineral composition and texture (e.g., intrusive vs. extrusive).
Sedimentary rocks: Classified by their formation process and sediment composition (e.g., clastic, chemical, or organic).
Metamorphic rocks: Classified by their texture and mineral composition, including the degree of foliation.
Using composition and texture:
Igneous rocks: Composition (e.g., felsic, mafic) and texture (e.g., coarse-grained, fine-grained).
Sedimentary rocks: Composition (e.g., sandstone, limestone) and texture (e.g., grain size, sorting).
Metamorphic rocks: Composition (e.g., presence of garnet, quartz) and texture (e.g., foliation, banding).
What are the different causes of melt?
Increased heat, pressure reduction (decompression melting), and the addition of volatiles (e.g., water or carbon dioxide).
What is viscosity?
The measure of a fluid's resistance to flow or its thickness, influencing how easily it can move or deform.
Why are there different igneous rocks from a single source of magma?
Variations arise due to differences in cooling rates, crystal formation, and mineral composition, influenced by factors such as pressure, temperature, and the presence of volatile components.
How are rocks recycled?
Rocks are recycled through the rock cycle, where they are transformed between igneous, sedimentary, and metamorphic forms through processes like melting, erosion, sedimentation, and metamorphism.
Active margin: A tectonic boundary where an oceanic plate is converging with a continental plate, typically characterized by high seismic activity, volcanoes, and rugged coastal features.
Arkose: A type of sandstone rich in feldspar, often resulting from the rapid erosion of granitic or metamorphic rocks and typically characterized by its coarse texture and reddish color.
Basin: A depression in the crust covering a large area; deeper part in crust or ocean.
Breccia: Coarse grain, particles are angular. They are closer to the source.
Carbonate: Anything related to calcite carbonate; commonly found in minerals such as calcite and dolomite, as well as in sedimentary rocks like limestone.
Conglomerate: A coarse-grained sedimentary rock composed of rounded gravel-sized clasts cemented together, often indicating high-energy environments like river channels or alluvial fans.
Continental shelf: Submerged edges of continents.
Craton: Stable interior of a continent; where we will find the oldest rock we can find on the planet.
Cross-bedding: Arrangement of beds or laminations in which one set of layers is inclined relative to others
Deep marine: The oceanic zone beyond the continental shelf, characterized by deep waters, low light levels, and sediment deposition mainly from turbidity currents, pelagic sedimentation, and biogenic activity.
Delta: A deposit where the river meets the ocean.
Depositional environment: The geographic location where sediments accumulate; refers to environmental factors under which sediment is deposited.
Flood plain: A flat, low-lying area adjacent to a river that is prone to periodic inundation during high water events, where sediments are deposited as the river overflows its banks.
Fluvial: Represents water flow; rivers and stream deposits.
Foraminifera: Single-celled organisms with shells, used to study sedimentary environments and climate through their fossils.
Graded bed: A sedimentary layer characterized by a gradual change in particle size from coarse at the bottom to fine at the top.
Graywacke sandstone: Quartz, feldspars, lithic fragments clasts, angular, lack cement but has a matrix of clay and silt; immature composition.
Lacustrine environment: Lakes; accumulate fine grained sediment and algae, resulting in mudrocks and shale.
Lithofacies: A facies is part of a rock body that has characteristics from which we can infer depositional environment
Maturity: Sorting, roundness and sphericity.
Mud cracks: Form in drying mud or sediment, indicating a once-wet surface that has since contracted and cracked as it dried.
Orogenic belt: Elongated regions bordering craton; was deformed by compressional forces.
Passive margin: A tectonic boundary between continental and oceanic plates that is not actively undergoing significant tectonic activity, characterized by broad, stable continental shelves and gentle slopes.
Platform: Sedimentary rock deposited on top of the shield rock; surrounds shield where ancient sediments were accumulated.
Reef: A marine ecosystem characterized by the presence of coral reefs or similar structures, which support diverse marine life and are built from calcium carbonate deposits.
Regression: The process where the sea level falls relative to the land, leading to the exposure of previously submerged areas and a shift in depositional environments.
Ripples: Rock structure where sand was moved by wind, streams, and coastal waves
Roundness/sphericity: Sediment grains are rounded during weathering and transportation.
Sandstone: A sedimentary rock composed primarily of sand-sized grains cemented together, typically exhibiting a granular texture and varying colors.
Shale: A fine-grained sedimentary rock formed from compacted mud and clay, characterized by its fissility, or the ability to split into thin layers.
Shallow marine: The coastal or nearshore zone of the ocean with relatively shallow water, active sedimentation, and high light levels.
Shield: Old crystalline basement rock that is exposed to the surface.
Siltstone: A fine-grained sedimentary rock composed primarily of silt-sized particles, often characterized by its smooth texture and layered appearance.
Sorting: The degree to which sediment grains are uniform in size, with well-sorted sediments having similar-sized particles and poorly sorted sediments containing a mix of sizes.
Subsidence: The sinking of land due to weight of deposits.
Till: Unsorted and unstratified sediment deposited directly by a glacier, consisting of a mixture of clay, silt, sand, gravel, and boulders; massive poorly sorted material; angular due to lack of weathering.
Tillite: A sedimentary rock formed from the consolidation of glacial till; angular and poorly sorted, not influenced by water.
Transgression: The process where sea level rises relative to the land, causing the sea to advance over previously exposed areas and shifting depositional environments inland.
Turbidites: Sedimentary deposits formed by turbidity currents, typically consisting of graded bedding with a sequence of fining-upward layers from coarse to fine materials.
Turbidity current: A fast-moving, sediment-laden flow of water that travels down underwater slopes, driven by gravity and density differences, often resulting in the deposition of graded beds.
What are depositional basins?
Depositional basins are large, low-lying geological structures where sediments accumulate over time, typically forming due to tectonic subsidence, and can become sites for significant sedimentary rock formation.
What is a craton? Shield? Platform?
Craton: A craton is a large, stable portion of the Earth's continental crust that has remained largely unaffected by tectonic activity for a significant geological time, consisting of ancient, consolidated rock.
Shield: A shield is a region of exposed Precambrian crystalline rock that forms the core of a craton, typically characterized by a lack of significant sedimentary cover.
Platform: A platform is a region of a craton where the ancient crystalline rock is covered by a relatively thin layer of sedimentary rock, extending beyond the shield area.
How and why do we use compositional and textural maturity?
Compositional and textural maturity are used to assess the degree of mineral stability and grain sorting in sediments, helping geologists interpret the sediment's transport history and depositional environment.
What are depositional environments? When looking at sedimentary rocks, can you determine what depositional environments they formed in?
Depositional environments are specific settings where sediments accumulate and eventually form sedimentary rocks, such as riverbeds, lakes, deserts, or marine settings. These environments influence the type and characteristics of sediments deposited.
Yes, features such as grain size, sorting, layering, and fossils provide clues about the conditions and processes at the time of deposition, such as whether the environment was aquatic, arid, or glacial.
What are sedimentary structures? What are examples and how do they form?
Sedimentary structures are physical features found within sedimentary rocks that result from the processes of sediment deposition and post-depositional alterations. They provide important information about the conditions and processes that occurred during sediment accumulation.
Examples: cross-bedding, graded bedding, mudcracks, ripple marks, fossil content
What is the difference between transgression and regression?
Transgression is when sea level rises and covers more land, leading to deeper-water sediments over time, while regression is when sea level falls and exposes more land, leading to shallower-water sediments over time.
Allopatric speciation: Occurs when a species is geographically separated into isolated populations, leading to the evolution of distinct species.
Analogy/ analogous: Refers to a similarity in function or structure between different species that evolved independently, not from a common ancestor.
Archaeopteryx: A transitional fossil that shows characteristics of both dinosaurs and birds, highlighting the evolutionary link between the two groups.
Biozone: A stratigraphic interval defined by the presence and range of particular fossil species, used to identify and correlate layers of rock in geological studies.
Carbonization: Soft tissues are preserved as thin films of carbon; the plant matter is gone.
Cast: A three-dimensional replica of an organism or object that forms when sediment fills a mold and hardens, preserving the shape of the original material.
Charles Darwin: A naturalist who developed the theory of evolution by natural selection, explaining how species evolve over time.
Coprolites: Fossilized feces, providing valuable information about the diet and behavior of ancient organisms.
Equus: The genus that includes modern horses, zebras, and donkeys, representing the only surviving branch of the once diverse horse family.
Erasmus Darwin: An 18th-century physician, poet, and natural philosopher who proposed early ideas about evolution and natural selection.
Evolution: The process by which species change over time through variations and natural selection, leading to the development of new species.
Fossil: Any recognizable evidence of preexisting life.
Gait: The manner or pattern of movement, particularly the way an animal or person walks.
Genotype: The genetic makeup of an organism, determining its inherited traits.
Homology/ homologous: Refers to traits in different species that share a common ancestry, though they may have different functions.
Inheritance of acquired characteristics: The discredited idea that traits developed during an organism's life can be passed on to its offspring.
Jean Baptiste de Monet: A French naturalist who proposed the theory of inheritance of acquired characteristics as a mechanism for evolution.
Mold: A hollow imprint or cavity in sedimentary rock that forms when an organism or object buried in sediment dissolves or decays, leaving a negative impression of its shape.
Natural Selection: The process by which organisms better adapted to their environment tend to survive and reproduce, passing on favorable traits to the next generation.
Paradigm shift: A fundamental change in the underlying assumptions or methodologies within a scientific discipline or broader field of knowledge.
Permineralization: Spread minerals throughout (water containing dissolved material deposits in organism’s remains).
Phenotype: The observable physical or biochemical characteristics of an organism, determined by its genotype and environmental influences.
Phyletic gradualism: The evolutionary model proposing that species evolve slowly and steadily through the accumulation of small changes over long periods.
Punctuated equilibrium: The evolutionary theory suggesting that species remain relatively unchanged for long periods, with significant evolutionary changes occurring rapidly during short, intense bursts.
Replacement: Simultaneous exchange of original substance of a dead plant or animal with mineral matter (solutions dissolve original material and replace).
Sympatric speciation: Occurs when new species evolve from a single ancestral species while inhabiting the same geographic region.
Trace fossil: A geological record of an organism's activity, such as footprints, burrows, or feeding marks, rather than the organism itself.
Vestigial structures: Body parts or organs that have lost most or all of their original function through evolution but remain as remnants in an organism.
What are the different types of fossils and how are they preserved?
Body Fossils: These are the remains of the actual organism, like bones, teeth, or shells, preserved through mineralization, where minerals replace organic material over time.
Molds and Casts: When an organism is buried, it may leave an impression (mold) in the surrounding rock. If the mold later fills with minerals, it forms a cast, which is a replica of the original organism.
Trace Fossils: These record the activity of organisms, such as footprints, burrows, or feces (coprolites), preserved as impressions in sediment that hardens over time.
Amber Fossils: Small organisms, like insects, get trapped in tree resin that hardens into amber, preserving them in great detail.
Permineralization: This process preserves the fine details of an organism, where mineral-rich water fills the pores of organic material, turning it into stone while retaining its structure.
Carbonization: Organic materials can be compressed over time, leaving a thin carbon film that outlines the organism, often found in soft-bodied organisms like leaves or fish.
What evidence do we have of evolution? Who were some of the scientists behind evolution and what did they contribute?
Evidence of Evolution:
Fossils: Show changes in species over time.
Comparative Anatomy: Similar structures suggest common ancestry.
Embryology: Early developmental similarities indicate evolutionary links.
Genetics: DNA reveals species relationships and evolution.
Biogeography: Species distribution supports evolutionary theory.
Scientists Behind Evolution:
Charles Darwin: Developed natural selection theory.
Alfred Russel Wallace: Co-developed natural selection ideas.
Jean-Baptiste Lamarck: Proposed early ideas on evolution.
Gregor Mendel: Discovered genetic inheritance principles.
Ernst Haeckel: Studied embryology and supported Darwin’s ideas.
What are some of the evolutionary terms discussed in class and how are they defined (e.g., homologous, vestigial, allopatric)?
Homologous: Traits in different species that come from a common ancestor.
Vestigial: Body parts that have lost their original function through evolution.
Allopatric: Speciation occurring when populations are geographically separated.
Movement of the Earth’s plates is though to be driven by what?
Thermal convection: the process of heat transfer in fluids caused by the movement of matter within them
It is believed that ____ caused denser materials to be near the center of Earth.
Partial melting and differentiation
Differentiation: the process of separation and organization of materials within a planet as it melts, forming layers and eventually continents. Comes down to density.
To qualify as a mineral, which of the following must always be true?
Mineral is crystalline
Which of the following minerals is last to crystallize in the Bowen’s Reaction Series?
Potassium Feldspar
Bowen’s Reaction Series: summarizes the order in which minerals crystallize from cooling basaltic magma.
Which of the following minerals is the most resistant (last to weather)?
Potassium Feldspar
Plutonic (intrusive) rocks possess ____ crystals.
Visible
Cools fast, forms deep underground.
Which of the following rock types has the highest viscosity as a melt?
Rhyolite
Viscosity: resistance to flow
Honey has high viscosity, water has low viscosity
Least likely to occur during collision of two tectonic plates.
Normal faults
What may occur during collision of two tectonic plates.
Metamorphism (heat and pressure), intrusions, arcuate or linear deformation belts
Earth’s mantle has a zone of weak, hot rock that is capable of flowing; this zone is known as the ____.
Asthenosphere
____ is the compaction and cementation of sediments forming sedimentary rocks.
Lithification
Metamorphic rocks possessing a foliated texture have what characteristic?
Parallel mineral alignment
This relative age dating principle assumes all sedimentary layers were originally deposited as flat layers.
Original horizontality
Dense ocean crust sinks below less-dense continental crust and into the mantle at ____.
Subduction zones
Age of the Earth: ~4.54 billion years
Contour line: Seen on topographic maps; close lines indicate steep slopes while further apart lines are lines of equal elevation.
Cross-section: A diagram that shows how different geological features are layered; may include rock types, folds, faults, dikes, and water passages.
Deep time: Immense amounts of time.
Evolution: A unifying theory for understanding history of life. It is the way that living systems move through time. Fossil records help show changes through time.
Hypothesis: A suggested idea put forward for consideration; it aligns with all current data and is likely to explain future observations. It is a limited explanation of the phenomenon.
Law: A concise statement of what will happen, but does not explain how or why they work.
Plate tectonics: The large-scale deformation of rocks in Earth's outer layers, serving as a comprehensive theory that explains many geological phenomena.
Science: Uses observations, experiments, and calculations to explain how things work, involving critical thinking through systematic steps that analyze scientific problems and yield verifiable results.
Scientific method: A systematic process used to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge. It typically involves making observations, forming a hypothesis, conducting experiments, analyzing the results, and drawing conclusions to test and refine the original hypothesis.
Theory: A hypothesis that has not yet been proven wrong; abundance of evidence. Explains how and/or why things happen; can be used to make predictions. Arises from tested hypotheses.
Topographic map: A detailed and accurate representation of natural and man-made features on the Earth's surface. It uses contour lines to show the elevation and shape of the terrain, providing information on the landscape's physical characteristics.
What is a topographic map? What is a contour line?
A topographic map displays detailed terrain features, including elevation, using contour lines to connect points of equal height.
Contour lines help visualize landforms and slopes, with their spacing indicating the steepness of the terrain.
What are cross-sections? How do you read a geologic map or cross-section?
Cross-sections are vertical views of the Earth's layers, showing their arrangement.
To read a geologic map, identify rock types and structures by their colors and symbols, then use cross-sections to see how these features change in depth and how they are arranged below the surface.
What is the scientific method? What is a hypothesis, a theory, a law, and what are the differences?
Scientific Method: A process of observation, hypothesis formation, experimentation, and analysis to gain knowledge.
Hypothesis: A testable, educated guess about a phenomenon.
Theory: A well-supported explanation of natural phenomena, based on evidence and tested hypotheses.
Law: A statement that describes a consistent natural pattern or relationship, often mathematically, without explaining why it occurs.
Differences:
Hypothesis: Specific and testable.
Theory: Broad, explanatory, and evidence-based.
Law: Describes what happens, often mathematically, without explanation.
Actualism: The natural laws and processes we observe today have always operated throughout Earth's history. Unlike uniformitarianism, it recognizes that the rates and intensities of these processes can vary over time, applying current natural laws to past events without assuming constant rates.
Australopithecus: Tracks found by Mary Leakey resolved an issue of early humankind. Did walking upright lead to brain development OR brain development lead to walking upright.
Charles Lyell: Formalized uniformitarianism, stressing consistent natural processes over time. He noted geological features cutting across rock are younger and emphasized relative dating.
East African Rift Valley: Continent is splitting apart and the wet volcanic ash preserves the footprints of elephants, three toed horses, saber-toothed cats, insects, and millipedes. Additionally, footprints of two Australopithecus afarensis individuals (the same species as the Lucy fossil) have been preserved.
Eons: The largest divisions of geological time, spanning billions of years.
Eras: Subdivisions of eons, each lasting hundreds of millions of years
James Hutton: The father of geology; best known for his theory of uniformitarianism and for proposing the concept of deep geological time.
Krakatoa: Volcanic eruption that occurred on a convergent plate boundary (where ocean crust collided with continental crust).
Mount Vesuvius: The volcanic eruption resulted from the convergence of the African and Eurasian plates. It buried the city of Pompeii under a combination of earthquakes, gases, ash, and mudflows.
Neptunism: The geological theory that all rocks originated from sedimented deposits of minerals in the Earth’s oceans.
Nicholas Steno: Father of stratigraphy (strata meaning layers); Recognized that rock layers were not all formed simultaneously and that variations in conditions resulted in different types of rocks. He also proposed that fossils were formed during the same time as the surrounding rocks.
Periods: Subdivisions of eras, typically lasting tens of millions of years.
Plutonism: The geological theory that rocks, especially igneous rocks, form from the cooling and solidification of molten magma beneath the Earth's surface.
Santorini Island: Catastrophic volcanic eruption that occurred during the Africa and Eurasian plate convergence. It was three to four rimes the magnitude of Krakatoa and likely ended the Minoan civilization.
Siccar Point: Outcrop and unconformity; deduced that all we see on this planet could be explained by these processes and time
Uniformitarianism: The principle that the same natural laws and processes that operate in the universe now have always operated in the past. It suggests that geological processes observed today can be used to interpret past geological events. This concept emphasizes consistency over time.
William Smith: Created first geologic map based largely in part on fossils.
What is uniformitarianism? Why is this important for understanding historical geology? What are some examples?
Uniformitarianism: The principle that the geological processes we observe today, like erosion and sedimentation, have been occurring in the same manner throughout Earth's history.
Importance: Allows geologists to use present-day observations to interpret and understand the Earth's geological past. Provides a consistent framework for studying and reconstructing the history of Earth’s surface and processes over long periods.
Examples: Erosion, sedimentation, volcanic activity, plate tectonics.
Who were some of the people that contributed to improving the science behind historical geology? What did they contribute?
Abraham Gottlob Werner - Developed the Neptunist theory, suggesting that rocks formed from crystallization in the early Earth's oceans, influencing early geological thought.
James Hutton - Introduced the concept of deep time and uniformitarianism, proposing that Earth's features were shaped by continuous and gradual processes over immense periods.
Charles Lyell - Popularized uniformitarianism, emphasizing that the same geological processes observed today have been shaping Earth throughout its history.
Nicholas Steno - Formulated foundational principles of stratigraphy, such as the law of superposition, which helped to understand the chronological order of rock layers.
William Smith - Created the first geological map and established the principle of faunal succession, using fossils to correlate rock layers and understand their relative ages.
What are the names and approximate ages of the Eons, Eras, and Periods?
What are examples of dramatic geologic events in the recent geologic past? What were some of the basics of those events (e.g., type of plate boundary)?
Krakatoa, Mt. Vesuvius, Santorini, East African Rift Valley, Australopithecus Tracks
Absolute age dating: Provides a precise age for rocks or fossils, giving a specific number of years since they were formed. This helps to create an accurate timeline of geological and archaeological events.
Angular conformity: Two layers of rock meet that are inclined or tilted at different angles to one another. The angled layers are beneath the new rock.
Correlation: The process of matching rocks found in different places (of equivalent age).
Cross-cutting relationships: Geologic features such as faults and dikes that cut through rock layers are younger than the rocks they intersect. These features indicate the most recent events when they are present.
Dike: A vertical or steeply inclined sheet of igneous rock that forms when magma forces its way through and solidifies across existing rock layers.
Disconformity: A gap between two sedimentary layers that are parallel; erosion, but no tilting.
Fault: A fracture or zone of fractures in the Earth's crust along which there has been movement and displacement of the rock on either side. Faults are caused by tectonic forces and can vary in size.
Faunal succession: Different organisms' fossils first appear at different times in the rock record. Related organisms' fossils show regular changes in progressively younger rocks wherever they are found. Once organisms become extinct, their fossils disappear from the rock record simultaneously and do not reappear in younger rocks.
Fossil: The preserved remains or traces of a living thing from long ago.
Inclusions: Objects enclosed in rock must be older than the rock itself. The objects must have existed before being embedded in the newer rock formation.
Index fossil: Fossils used to define and identify geologic periods; considered units of study in biostratigraphy. The fossils must be wide spread, fast evolving, common, easily preserved, and easily identified.
Lateral continuity: Rock layers initially extend laterally in all directions until they thin out or reach a physical barrier. This suggests that rock layers that are now separated by a valley or other erosional features were once continuous.
Nonconformity: Where sedimentary or volcanic rocks lie directly on igneous or metamorphic rocks.
Original horizontality: A tectonic force tilts the sedimentary layers up. Using superposition, we know the bottom rock is the oldest, the top rock is the youngest, and the most recent event is the tectonic tilt.
Relative age dating: Involves examining rocks in the field to determine the sequence of events that created them. It establishes the order of events without specifying the exact time they occurred.
Sequence: Order of events.
Stratigraphy: The branch of geology that studies rock layers (strata) and layering (stratification).
Sequence stratigraphy: Based on changes in global sea levels over time.
Superposition: Rock on the top is younger, rock on the bottom is older.
Unconformity: An erosional gap in the geological record within rock layers, representing a period of erosion or non-deposition.
What is relative age dating?
A method used to determine if one rock or fossil is older or younger than another without knowing their exact ages. This is done by looking at the positions of rock layers and the fossils within them.
What are the relative age dating principles and how are they used?
Superposition - Determine the relative ages of sedimentary rock layers.
Original Horizontality - If rock layers are found tilted or folded, it indicates that they have been disturbed after their initial deposition.
Cross-Cutting Relationships - Used to determine the relative ages of the features by observing which ones cut across others.
Inclusions - Used to determine that the rock containing the fragments is younger than the fragments themselves.
Lateral Continuity - Used to match rock layers that have been separated by erosion or other geological events.
Faunal Succession - Use fossils within rock layers to correlate the ages of rocks from different locations.
What is sequence stratigraphy?
A method of studying sedimentary rock layers (strata) and their temporal and spatial relationships to understand the geological history of sediment deposition and sea level changes.
What is an unconformity and what are the different types?
A surface in the rock record that represents a period of erosion or non-deposition, indicating a gap in the geological history. Types are angular, disconformity, and nonconformity.
How do we use the relative age dating principles in chronologically ordering layers in a cross-section?
Examine the cross-section to identify the various rock layers and their relationships.
Order the layers from oldest at the bottom to youngest at the top.
Confirm that any layers that are not horizontal have been altered after deposition. Adjust the order if necessary to reflect the original sequence.
Determine the relative ages of features such as faults or intrusions. The features cutting through other layers are younger than the layers they disrupt.
Identify any rock fragments (inclusions) within the layers. The layer containing the inclusions is younger than the fragments.
Use fossils within the layers to correlate and date the layers, ensuring that the fossil content is consistent with the known sequence of fossil appearance and extinction.
Absolute age dating: A method used to determine the exact age of a rock, fossil, or other object in years. This is achieved through techniques such as radiometric dating.
Acasta Gneiss: The oldest intact rock on Earth; type of metamorphic rock. Age is ~4.0 Ga
Daughter isotope: The new isotope.
Half-life: The amount of time it takes for ½ of parent isotopes to decay to daughter
Henri Becquerel: Discovered radioactivity in 1896.
Isotopes: Versions of elements that have different numbers of neutrons and, as a result, different atomic weights.
Lord Kelvin: Published the first of several heat-flow calculations for cooling Earth. Used laws of heat convection and radiation to estimate Earth’s age, it was older than he predicted.
Marie Curie: Discovered the elements radium and polonium were radioactive while investigating the radioactivity of the mineral pitchblende (uraninite); coined “Radioactivity” as a term denoting emissions in Radium. 1st woman to win Nobel Prize.
Parent isotope: The original, radioactive isotope.
Radioactive decay: Measures the decay of radioactive isotopes within the material to calculate how long it has been since the object was formed; provides the basis for modern isotopic dating.
Radioactivity: The spontaneous emission of particles or energy from the unstable nucleus of an atom as it transforms into a more stable form; produces heat.
Radiocarbon dating: A technique used to find out how old something is by measuring the amount of carbon-14 it contains. This method is useful for dating materials that were once alive
Radiometric dating: A method used to determine the age or history of an object, i.e. the Earth, by measuring the amount of certain radioactive elements it contains and how they decay over time.
Relative age dating: Determines the age of a rock or fossil in comparison to other objects; doesn't provide an exact age, tells us whether something is older or younger than something else. Done by looking at position of rock layers and fossils (superposition).
Zircon: Minerals that contain zirconium and can be used to date rocks because they preserve age information from uranium decay over billions of years.
What is absolute age dating and how do we determine absolute ages?
Absolute age dating is a method used to determine the exact age of a rock, fossil, or other object in years.
Radiometric dating measures the decay of radioactive isotopes within the material.
What are parent and daughter isotopes? What is a half-life?
Parent isotope - the original, radioactive isotopes.
Daughter isotope - the new isotope.
Half-life - amount of time it takes for ½ of parent isotopes to decay to daughter.
What geologic events can we date?
We can date events like volcanic eruptions, sediment formation, metamorphic changes, faulting, erosion, and fossilization using various dating methods.
How do we know absolute dating works?
Ages confirmed by historical observations.
Ages agree with superposition.
Ages on one rock determined by multiple dating methods in different labs agree.
Ages are consistent with known geologic or solar system history.
How would we date sedimentary rocks?
Radiometric Dating: Date minerals within the sedimentary rock, such as zircon, to determine the age of the rock formation.
Fossils: Use fossils within the rock to correlate with known ages from other locations.
Stratigraphy: Apply principles like the Law of Superposition to compare the relative ages of sedimentary layers.
Andesite: Igneous, type of volcanic rock that is gray to dark gray in color and forms from lava that is intermediate in composition between basalt and rhyolite.
Aphanitic: Type of texture that contains small, fine grained crystals due to fast cooling; usually extrusive, but not always. Examples: rhyolite, andesite, basalt
Assimilation: When molten rock (magma) melts and incorporates surrounding rock, changing the magma's composition.
Basalt: Igneous, a dark-colored, fine-grained volcanic rock that forms from the rapid cooling of low-viscosity lava rich in iron and magnesium.
Carbonate: Sedimentary; chemically or biologically precipitated, marine.
Chalk: Sedimentary, a soft, white, fine-grained sedimentary rock composed mainly of the mineral calcite, which forms from the accumulation of tiny marine organisms' shells and skeletons.
Chert: Sedimentary, a hard, fine-grained sedimentary rock made mostly of silica, often formed from marine organisms' remains or silica precipitation.
Clastic: Composed of mineral grains weathered from pre-existing rock and cemented together by precipitated minerals. Gravel → Sand → Silt → Clay
Cleavage: The tendency of a mineral to break along specific planes of weakness, resulting in smooth, flat surfaces; how minerals split.
Coal: Sedimentary; made of plant matter.
Crystal habit: The characteristic shape and form of a mineral crystal, including its overall growth pattern and the arrangement of its faces.
Decompression: The reduction of pressure or stress on magma, allowing it to rise and potentially solidify as it moves towards the Earth's surface.
Deposition: When materials like sand, silt, or gravel settle out of water or wind and build up in new locations.
Evaporite: Minerals that form from the evaporation of water, leaving behind solid deposits like salt or gypsum.
Extrusive: Type of igneous rocks that form from the rapid cooling and solidification of lava on Earth's surface; volcanic rocks, crystals are not present.
Felsic: A type of igneous rock that are light in color and rich in silica and aluminum, containing minerals such as quartz and feldspar. They typically form from magma that cools slowly underground. More silica, high viscosity.
Foliated: A planar alignment of metamorphic minerals (especially micas) with mineral alignment perpendicular to highest stress direction; differential pressure (or stress) is applied.
Fractional crystallization: A process where different minerals crystallize from molten rock (magma) at different temperatures, causing the composition of the remaining magma to change over time.
Frothy: A rock with this texture has a bubbly or spongy appearance, often due to trapped gas bubbles in the volcanic glass or lava that cooled quickly.
Gabbro: Igneous, a dark, coarse-grained rock with a phaneritic texture that forms from the slow cooling of magma beneath the Earth's surface, composed mainly of minerals like plagioclase and pyroxene.
Glassy: Texture in minerals that occurs when molten lava cools so quickly that crystals do not have time to form. Example: obsidian
Gneiss: Metamorphic, a high-grade rock characterized by its layered or banded appearance, formed from the alteration of granite or other rocks under high pressure and temperature.
Granite: Igneous rock
Halite: A mineral commonly known as rock salt, composed of sodium chloride (NaCl), and often forms from the evaporation of seawater.
Hardness: A measure of how resistant a mineral is to scratching or abrasion.
Heat transfer: The movement of thermal energy within the Earth, occurring through conduction, convection, or radiation.
Igneous rock: Forms from the cooling and solidification of molten a melt (magma or lava).
Intermediate: An igneous rock with a composition between that of basalt and granite, containing moderate amounts of silica and a mix of light and dark minerals.
Intrusive:
Lava: Melt above Earth’s surface.
Limestone: Sedimentary rock primarily composed of calcium carbonate, often formed from the remains of marine organisms like coral and shells.
Luster: The way a mineral reflects light from its surface. It describes the quality and appearance of the shine, which can be categorized as metallic, vitreous (glass-like), pearly, silky, or dull.
Mafic: Dark-colored igneous rocks that are rich in iron and magnesium, with minerals like pyroxene and olivine. Less silica, low viscosity.
Magma: Melt below Earth’s surface.
Magmatic differentiation: Process by which different rocks form from a single magma.
Metamorphic grade: Change of texture and mineral; progressive change in which minerals grow as a function of pressure and temperature. Low grade = can’t see minerals, intermediate grade = can see minerals, high grade = banded minerals.
Metamorphic rock: Formed from the alteration of existing rocks (igneous, sedimentary, or other metamorphic rocks) through heat, pressure, and chemical processes, resulting in new mineralogical and structural features.
Mineral: A naturally occurring, inorganic solid with a specific chemical composition and a crystalline structure.
Non-foliated: Metamorphic rocks that lack a layered or banded appearance, with minerals that are recrystallized without a preferred orientation; uniform pressure (or stress) is applied.
Partial melting: The process where only a portion of a rock melts to form magma, while the rest remains solid.
Pegmatitic: A texture in igneous rocks where the mineral crystals are exceptionally large and coarse-grained, often forming in the final stages of magma crystallization.
Phaneritic: A texture in intrusive igneous rocks where the mineral crystals are large enough to be seen with the naked eye, indicating that the rock cooled slowly beneath the Earth's surface.
Phyllite: A type of metamorphic rock that is intermediate between slate and schist, characterized by a shiny, slightly wavy surface and fine-grained texture.
Plutonic rocks: Type of igneous rock; slow cooling and solidification of magma beneath Earth's surface, intrusive.
Porphyritic: A texture in igneous rocks where large crystals, called phenocrysts, are embedded in a finer-grained or glassy groundmass.
Protolith: Pre-existing rock of new metamorphic rock.
Rock cycle: A continuous process where rocks are transformed between igneous, sedimentary, and metamorphic forms through geological processes like melting, erosion, and pressure changes.
Rhyolite: Igneous rock; light-colored, fine-grained volcanic rock that is high in silica and typically contains minerals like quartz and feldspar.
Sedimentary rock: Formed from the accumulation, compaction, and cementation of sediments, which can include fragments of other rocks, minerals, and organic materials.
Schist: A type of metamorphic rock characterized by its foliated texture, with visible layers or bands of minerals like mica, quartz, and garnet, formed under high pressure and temperature conditions.
Silicates: The dominate class. Minerals that contain silicon and oxygen, typically combined with other elements like aluminum, iron, magnesium, or potassium. They are the most common group of minerals in Earth's crust, including minerals like quartz, feldspar, and mica.
Slate: A fine-grained metamorphic rock that forms from the metamorphism of shale, characterized by its ability to break into thin, flat layers.
Solid-state change: The transformation of a rock's mineral composition and structure without melting, through processes like heat and pressure, which leads to the formation of new minerals and textures.
Streak: The color of a mineral's powder when it is scraped across a porcelain plate or streak plate
Ultramafic: Igneous rocks that are very low in silica and high in iron and magnesium, often containing minerals like olivine and pyroxene.
Vesicular: A texture in volcanic rocks characterized by numerous gas bubbles or vesicles trapped within the rock, giving it a porous appearance.
Viscosity: Resistance to flow; depends on temperature, volatile content, and silica content.
Volatiles: Substances that easily evaporate or turn into gas at relatively low temperatures.
Volcanic rock: Type of igneous rock, forms from the rapid cooling and solidification of lava on the Earth's surface, extrusive.
What are minerals? What are the physical properties used to identify them?
Minerals: Naturally occurring, inorganic solid substances with a definite chemical composition and crystalline structure.
Physical properties used to identify minerals: Hardness, color, streak, luster, cleavage, fracture, and specific gravity.
What are the dominant elements in our crust? What is the dominant class of minerals?
Dominant elements in our crust: Oxygen and silicon.
Dominant class of minerals: Silicates.
What are the major rock groups and how do they form? How are they classified? How do we use composition and texture to classify each rock type?
Major rock groups and their formation:
Igneous rocks: Formed from the cooling and solidification of magma or lava.
Sedimentary rocks: Formed from the accumulation, compaction, and cementation of sediments.
Metamorphic rocks: Formed from the alteration of existing rocks through heat, pressure, or chemically active fluids.
Classification:
Igneous rocks: Classified by their mineral composition and texture (e.g., intrusive vs. extrusive).
Sedimentary rocks: Classified by their formation process and sediment composition (e.g., clastic, chemical, or organic).
Metamorphic rocks: Classified by their texture and mineral composition, including the degree of foliation.
Using composition and texture:
Igneous rocks: Composition (e.g., felsic, mafic) and texture (e.g., coarse-grained, fine-grained).
Sedimentary rocks: Composition (e.g., sandstone, limestone) and texture (e.g., grain size, sorting).
Metamorphic rocks: Composition (e.g., presence of garnet, quartz) and texture (e.g., foliation, banding).
What are the different causes of melt?
Increased heat, pressure reduction (decompression melting), and the addition of volatiles (e.g., water or carbon dioxide).
What is viscosity?
The measure of a fluid's resistance to flow or its thickness, influencing how easily it can move or deform.
Why are there different igneous rocks from a single source of magma?
Variations arise due to differences in cooling rates, crystal formation, and mineral composition, influenced by factors such as pressure, temperature, and the presence of volatile components.
How are rocks recycled?
Rocks are recycled through the rock cycle, where they are transformed between igneous, sedimentary, and metamorphic forms through processes like melting, erosion, sedimentation, and metamorphism.
Active margin: A tectonic boundary where an oceanic plate is converging with a continental plate, typically characterized by high seismic activity, volcanoes, and rugged coastal features.
Arkose: A type of sandstone rich in feldspar, often resulting from the rapid erosion of granitic or metamorphic rocks and typically characterized by its coarse texture and reddish color.
Basin: A depression in the crust covering a large area; deeper part in crust or ocean.
Breccia: Coarse grain, particles are angular. They are closer to the source.
Carbonate: Anything related to calcite carbonate; commonly found in minerals such as calcite and dolomite, as well as in sedimentary rocks like limestone.
Conglomerate: A coarse-grained sedimentary rock composed of rounded gravel-sized clasts cemented together, often indicating high-energy environments like river channels or alluvial fans.
Continental shelf: Submerged edges of continents.
Craton: Stable interior of a continent; where we will find the oldest rock we can find on the planet.
Cross-bedding: Arrangement of beds or laminations in which one set of layers is inclined relative to others
Deep marine: The oceanic zone beyond the continental shelf, characterized by deep waters, low light levels, and sediment deposition mainly from turbidity currents, pelagic sedimentation, and biogenic activity.
Delta: A deposit where the river meets the ocean.
Depositional environment: The geographic location where sediments accumulate; refers to environmental factors under which sediment is deposited.
Flood plain: A flat, low-lying area adjacent to a river that is prone to periodic inundation during high water events, where sediments are deposited as the river overflows its banks.
Fluvial: Represents water flow; rivers and stream deposits.
Foraminifera: Single-celled organisms with shells, used to study sedimentary environments and climate through their fossils.
Graded bed: A sedimentary layer characterized by a gradual change in particle size from coarse at the bottom to fine at the top.
Graywacke sandstone: Quartz, feldspars, lithic fragments clasts, angular, lack cement but has a matrix of clay and silt; immature composition.
Lacustrine environment: Lakes; accumulate fine grained sediment and algae, resulting in mudrocks and shale.
Lithofacies: A facies is part of a rock body that has characteristics from which we can infer depositional environment
Maturity: Sorting, roundness and sphericity.
Mud cracks: Form in drying mud or sediment, indicating a once-wet surface that has since contracted and cracked as it dried.
Orogenic belt: Elongated regions bordering craton; was deformed by compressional forces.
Passive margin: A tectonic boundary between continental and oceanic plates that is not actively undergoing significant tectonic activity, characterized by broad, stable continental shelves and gentle slopes.
Platform: Sedimentary rock deposited on top of the shield rock; surrounds shield where ancient sediments were accumulated.
Reef: A marine ecosystem characterized by the presence of coral reefs or similar structures, which support diverse marine life and are built from calcium carbonate deposits.
Regression: The process where the sea level falls relative to the land, leading to the exposure of previously submerged areas and a shift in depositional environments.
Ripples: Rock structure where sand was moved by wind, streams, and coastal waves
Roundness/sphericity: Sediment grains are rounded during weathering and transportation.
Sandstone: A sedimentary rock composed primarily of sand-sized grains cemented together, typically exhibiting a granular texture and varying colors.
Shale: A fine-grained sedimentary rock formed from compacted mud and clay, characterized by its fissility, or the ability to split into thin layers.
Shallow marine: The coastal or nearshore zone of the ocean with relatively shallow water, active sedimentation, and high light levels.
Shield: Old crystalline basement rock that is exposed to the surface.
Siltstone: A fine-grained sedimentary rock composed primarily of silt-sized particles, often characterized by its smooth texture and layered appearance.
Sorting: The degree to which sediment grains are uniform in size, with well-sorted sediments having similar-sized particles and poorly sorted sediments containing a mix of sizes.
Subsidence: The sinking of land due to weight of deposits.
Till: Unsorted and unstratified sediment deposited directly by a glacier, consisting of a mixture of clay, silt, sand, gravel, and boulders; massive poorly sorted material; angular due to lack of weathering.
Tillite: A sedimentary rock formed from the consolidation of glacial till; angular and poorly sorted, not influenced by water.
Transgression: The process where sea level rises relative to the land, causing the sea to advance over previously exposed areas and shifting depositional environments inland.
Turbidites: Sedimentary deposits formed by turbidity currents, typically consisting of graded bedding with a sequence of fining-upward layers from coarse to fine materials.
Turbidity current: A fast-moving, sediment-laden flow of water that travels down underwater slopes, driven by gravity and density differences, often resulting in the deposition of graded beds.
What are depositional basins?
Depositional basins are large, low-lying geological structures where sediments accumulate over time, typically forming due to tectonic subsidence, and can become sites for significant sedimentary rock formation.
What is a craton? Shield? Platform?
Craton: A craton is a large, stable portion of the Earth's continental crust that has remained largely unaffected by tectonic activity for a significant geological time, consisting of ancient, consolidated rock.
Shield: A shield is a region of exposed Precambrian crystalline rock that forms the core of a craton, typically characterized by a lack of significant sedimentary cover.
Platform: A platform is a region of a craton where the ancient crystalline rock is covered by a relatively thin layer of sedimentary rock, extending beyond the shield area.
How and why do we use compositional and textural maturity?
Compositional and textural maturity are used to assess the degree of mineral stability and grain sorting in sediments, helping geologists interpret the sediment's transport history and depositional environment.
What are depositional environments? When looking at sedimentary rocks, can you determine what depositional environments they formed in?
Depositional environments are specific settings where sediments accumulate and eventually form sedimentary rocks, such as riverbeds, lakes, deserts, or marine settings. These environments influence the type and characteristics of sediments deposited.
Yes, features such as grain size, sorting, layering, and fossils provide clues about the conditions and processes at the time of deposition, such as whether the environment was aquatic, arid, or glacial.
What are sedimentary structures? What are examples and how do they form?
Sedimentary structures are physical features found within sedimentary rocks that result from the processes of sediment deposition and post-depositional alterations. They provide important information about the conditions and processes that occurred during sediment accumulation.
Examples: cross-bedding, graded bedding, mudcracks, ripple marks, fossil content
What is the difference between transgression and regression?
Transgression is when sea level rises and covers more land, leading to deeper-water sediments over time, while regression is when sea level falls and exposes more land, leading to shallower-water sediments over time.
Allopatric speciation: Occurs when a species is geographically separated into isolated populations, leading to the evolution of distinct species.
Analogy/ analogous: Refers to a similarity in function or structure between different species that evolved independently, not from a common ancestor.
Archaeopteryx: A transitional fossil that shows characteristics of both dinosaurs and birds, highlighting the evolutionary link between the two groups.
Biozone: A stratigraphic interval defined by the presence and range of particular fossil species, used to identify and correlate layers of rock in geological studies.
Carbonization: Soft tissues are preserved as thin films of carbon; the plant matter is gone.
Cast: A three-dimensional replica of an organism or object that forms when sediment fills a mold and hardens, preserving the shape of the original material.
Charles Darwin: A naturalist who developed the theory of evolution by natural selection, explaining how species evolve over time.
Coprolites: Fossilized feces, providing valuable information about the diet and behavior of ancient organisms.
Equus: The genus that includes modern horses, zebras, and donkeys, representing the only surviving branch of the once diverse horse family.
Erasmus Darwin: An 18th-century physician, poet, and natural philosopher who proposed early ideas about evolution and natural selection.
Evolution: The process by which species change over time through variations and natural selection, leading to the development of new species.
Fossil: Any recognizable evidence of preexisting life.
Gait: The manner or pattern of movement, particularly the way an animal or person walks.
Genotype: The genetic makeup of an organism, determining its inherited traits.
Homology/ homologous: Refers to traits in different species that share a common ancestry, though they may have different functions.
Inheritance of acquired characteristics: The discredited idea that traits developed during an organism's life can be passed on to its offspring.
Jean Baptiste de Monet: A French naturalist who proposed the theory of inheritance of acquired characteristics as a mechanism for evolution.
Mold: A hollow imprint or cavity in sedimentary rock that forms when an organism or object buried in sediment dissolves or decays, leaving a negative impression of its shape.
Natural Selection: The process by which organisms better adapted to their environment tend to survive and reproduce, passing on favorable traits to the next generation.
Paradigm shift: A fundamental change in the underlying assumptions or methodologies within a scientific discipline or broader field of knowledge.
Permineralization: Spread minerals throughout (water containing dissolved material deposits in organism’s remains).
Phenotype: The observable physical or biochemical characteristics of an organism, determined by its genotype and environmental influences.
Phyletic gradualism: The evolutionary model proposing that species evolve slowly and steadily through the accumulation of small changes over long periods.
Punctuated equilibrium: The evolutionary theory suggesting that species remain relatively unchanged for long periods, with significant evolutionary changes occurring rapidly during short, intense bursts.
Replacement: Simultaneous exchange of original substance of a dead plant or animal with mineral matter (solutions dissolve original material and replace).
Sympatric speciation: Occurs when new species evolve from a single ancestral species while inhabiting the same geographic region.
Trace fossil: A geological record of an organism's activity, such as footprints, burrows, or feeding marks, rather than the organism itself.
Vestigial structures: Body parts or organs that have lost most or all of their original function through evolution but remain as remnants in an organism.
What are the different types of fossils and how are they preserved?
Body Fossils: These are the remains of the actual organism, like bones, teeth, or shells, preserved through mineralization, where minerals replace organic material over time.
Molds and Casts: When an organism is buried, it may leave an impression (mold) in the surrounding rock. If the mold later fills with minerals, it forms a cast, which is a replica of the original organism.
Trace Fossils: These record the activity of organisms, such as footprints, burrows, or feces (coprolites), preserved as impressions in sediment that hardens over time.
Amber Fossils: Small organisms, like insects, get trapped in tree resin that hardens into amber, preserving them in great detail.
Permineralization: This process preserves the fine details of an organism, where mineral-rich water fills the pores of organic material, turning it into stone while retaining its structure.
Carbonization: Organic materials can be compressed over time, leaving a thin carbon film that outlines the organism, often found in soft-bodied organisms like leaves or fish.
What evidence do we have of evolution? Who were some of the scientists behind evolution and what did they contribute?
Evidence of Evolution:
Fossils: Show changes in species over time.
Comparative Anatomy: Similar structures suggest common ancestry.
Embryology: Early developmental similarities indicate evolutionary links.
Genetics: DNA reveals species relationships and evolution.
Biogeography: Species distribution supports evolutionary theory.
Scientists Behind Evolution:
Charles Darwin: Developed natural selection theory.
Alfred Russel Wallace: Co-developed natural selection ideas.
Jean-Baptiste Lamarck: Proposed early ideas on evolution.
Gregor Mendel: Discovered genetic inheritance principles.
Ernst Haeckel: Studied embryology and supported Darwin’s ideas.
What are some of the evolutionary terms discussed in class and how are they defined (e.g., homologous, vestigial, allopatric)?
Homologous: Traits in different species that come from a common ancestor.
Vestigial: Body parts that have lost their original function through evolution.
Allopatric: Speciation occurring when populations are geographically separated.
Movement of the Earth’s plates is though to be driven by what?
Thermal convection: the process of heat transfer in fluids caused by the movement of matter within them
It is believed that ____ caused denser materials to be near the center of Earth.
Partial melting and differentiation
Differentiation: the process of separation and organization of materials within a planet as it melts, forming layers and eventually continents. Comes down to density.
To qualify as a mineral, which of the following must always be true?
Mineral is crystalline
Which of the following minerals is last to crystallize in the Bowen’s Reaction Series?
Potassium Feldspar
Bowen’s Reaction Series: summarizes the order in which minerals crystallize from cooling basaltic magma.
Which of the following minerals is the most resistant (last to weather)?
Potassium Feldspar
Plutonic (intrusive) rocks possess ____ crystals.
Visible
Cools fast, forms deep underground.
Which of the following rock types has the highest viscosity as a melt?
Rhyolite
Viscosity: resistance to flow
Honey has high viscosity, water has low viscosity
Least likely to occur during collision of two tectonic plates.
Normal faults
What may occur during collision of two tectonic plates.
Metamorphism (heat and pressure), intrusions, arcuate or linear deformation belts
Earth’s mantle has a zone of weak, hot rock that is capable of flowing; this zone is known as the ____.
Asthenosphere
____ is the compaction and cementation of sediments forming sedimentary rocks.
Lithification
Metamorphic rocks possessing a foliated texture have what characteristic?
Parallel mineral alignment
This relative age dating principle assumes all sedimentary layers were originally deposited as flat layers.
Original horizontality
Dense ocean crust sinks below less-dense continental crust and into the mantle at ____.
Subduction zones
