Studied by 31 people
A map that displays detailed terrain features, including elevation, using contour lines to connect points of equal height.
Topographic map
Lines that help visualize landforms and slopes, with their spacing indicating the steepness of the terrain.
Contour line
Vertical views of the Earth's layers, showing their arrangement.
Cross-sections
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.
How do you read a geologic map or cross-section?
A process of observation, hypothesis formation, experimentation, and analysis to gain knowledge.
The Scientific Method
A testable, educated guess about a phenomenon.
Hypothesis
A well-supported explanation of natural phenomena, based on evidence and tested hypotheses.
Theory
A statement that describes a consistent natural pattern or relationship, often mathematically, without explaining why it occurs.
Law
Hypothesis: Specific and testable.
Theory: Broad, explanatory, and evidence-based.
Law: Describes what happens, often mathematically, without explanation.
What are the differences between hypothesis, theory, and law?
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.
What is uniformitarianism?
Why is this important for understanding historical geology?
What are some examples?
Abraham Gottlob Werner
James Hutton
Charles Lyell
Nicholas Steno
William Smith
Who were some of the people that contributed to improving the science behind historical geology?
Created the first geological map and established the principle of faunal succession, using fossils to correlate rock layers and understand their relative ages.
William Smith
Formulated foundational principles of stratigraphy, such as the law of superposition, which helped to understand the chronological order of rock layers.
Nicholas Steno
Popularized uniformitarianism, emphasizing that the same geological processes observed today have been shaping Earth throughout its history.
Charles Lyell
Introduced the concept of deep time and uniformitarianism, proposing that Earth's features were shaped by continuous and gradual processes over immense periods.
James Hutton
Developed the Neptunist theory, suggesting that rocks formed from crystallization in the early Earth's oceans, influencing early geological thought.
Abraham Gottlob Werner
Phanerozoic
Proterozoic
Archean
Hadien
Eons
Cenozoic
Mesozoic
Paleozoic
Neoproterozoic
Eras
Quaternary
Neogene
Paleogene
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Ediacaran
Cryogenian
Periods
Krakatoa
Mt. Vesuvius
Santorini
East African Rift Valley
Australopithecus Tracks
What are examples of dramatic geologic events in the recent geologic past?
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 is relative age dating?
Superposition
Original Horizontality
Cross-Cutting Relationships
Inclusions
Lateral Continuity
Faunal Succession
What are the relative age dating principles?
Use fossils within rock layers to correlate the ages of rocks from different locations.
Faunal Succession
Used to match rock layers that have been separated by erosion or other geological events.
Lateral Continuity
Used to determine that the rock containing the fragments is younger than the fragments themselves.
Inclusions
Used to determine the relative ages of the features by observing which ones cut across others.
Cross-Cutting Relationships
If rock layers are found tilted or folded, it indicates that they have been disturbed after their initial deposition.
Original Horizontality
Determine the relative ages of sedimentary rock layers.
Superposition
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 sequence stratigraphy?
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.
What is an unconformity and what are the different types?
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.
How do we use the relative age dating principles in chronologically ordering layers in a cross-section?
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 is absolute age dating and how do we determine absolute ages?
The original, radioactive isotope.
What is a parent isotope?
The new isotope.
What is a daughter isotope?
Amount of time it takes for ½ of parent isotopes to decay to daughter.
What is a half-life?
Volcanic eruptions, sediment formation, metamorphic changes, faulting, erosion, and fossilization using various dating methods.
What geologic events can we date?
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 do we know absolute dating works?
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.
How would we date sedimentary rocks?
Naturally occurring, inorganic solid substances with a definite chemical composition and crystalline structure.
What are minerals?
Hardness, color, streak, luster, cleavage, fracture, and specific gravity.
What are the physical properties used to identify minerals?
Oxygen and silicon
What are the dominant elements in our crust?
Silicates
What is the dominant class of minerals?
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.
What are the major rock groups and how do they form?
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.
How are rock groups classified?
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).
How do we use composition and texture to classify each rock type?
Increased heat, pressure reduction (decompression melting), and the addition of volatiles (e.g., water or carbon dioxide).
What are the different causes of melt?
The measure of a fluid's resistance to flow or its thickness, influencing how easily it can move or deform.
What is viscosity?
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.
Why are there different igneous rocks from a single source of magma?
Through the rock cycle, where they are transformed between igneous, sedimentary, and metamorphic forms through processes like melting, erosion, sedimentation, and metamorphism.
How are rocks recycled?
Note 
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