Geology UPCAT Review

Flashcards containing vocabulary terms and definitions related to Earth science topics, including the Earth's structure, mineral properties, rock types, plate tectonics, geological time scale, and stratigraphy.

Atmosphere

A collective layer of gas that envelopes the Earth, divided into layers, shielding from UV rays, maintaining warmth, and containing essential gases.

Hydrosphere

The bodies of water on Earth, including surface water and groundwater, covering nearly 71% of the Earth's surface, mostly saline (97.4%) with a smaller fresh water portion (2.6%).

Biosphere

The region where all biological life resides.

Geosphere

The largest of Earth's spheres, comprising external and internal processes.

Crust

The thinnest and outermost layer of the Earth.

Continental crust

Older and more buoyant type of crust, averaging 35km thick, composed mainly of granite.

Oceanic crust

Younger and denser crust, averaging 7km thick, composed of basalt.

Mantle

The layer that comprises most of the earth's volume, begins where the crust ends at a depth of 2,900 km.

Mohorovičić Discontinuity

Boundary between the crust and the mantle, marked by a chemical composition change

Repetti discontinuity

The boundary that separates the upper and lower mantle.

Core

Comprises of Fe-Ni (iron-nickel) alloy with a density around 11 g/cm^3.

Gutenberg discontinuity

The mantle-core boundary where the core begins, located at the 2,900 km depth.

Asthenosphere

A mechanically weak layer consisting of the lower portion of the upper mantle extending to 660 km, crucial in plate tectonics.

Mesosphere

Comprised of the lower mantle, reaching the 2,900 km depth.

Outer core

Mechanical layer made out of liquid, melted Fe-Ni alloy responsible for the earth's magnetic field.

Lehmann discontinuity

The outer-inner core boundary

Inner core

Solid ball of mostly Fe (iron).

Minerals

Naturally-occurring, inorganic, homogeneous solid with a definite chemical composition and ordered crystalline structure.

Luster

Describes how light is reflected from the mineral's surface.

Moh's hardness scale

Tool used to describe a mineral's hardness relative to other materials.

Cleavage/fracture

Refers to the tendency of a mineral to break along preferred planes called zones of weakness.

Tenacity

Describes how well a mineral can handle stress, such as breaking, crushing, bending, or tearing.

Diaphaneity

Refers to how well light travels through a mineral

Effervescence

Refers to the reaction to a strong acid, such as HCl (hydrochloric acid).

Silicates

Most common mineral group that uses oxygen and silicon as building blocks.

Rocks

Naturally-occurring aggregates of mineral and mineraloids.

Igneous rocks

Formed when molten material cools and solidifies.

Intrusive igneous

Igneous rocks that form below the earth's surface, also called plutonic rocks.

Extrusive igneous

Igneous rocks that form on the surface and are also called volcanic rocks.

Sedimentary rocks

Formed from loose materials called sediment that have been eroded and then buried and compacted in a process called diagenesis.

Clastic sedimentary rocks

Classified based on the characteristics of their clasts, such as size, angularity/roundness, and sorting.

Chemical sedimentary rocks

Formed when water evaporates, leaving behind dissolved materials.

Biochemical/organic sedimentary rocks

Composed of the remains of living things (shells, bones, plant fragments, etc.).

Metamorphic rocks

A rock is subjected to certain chemical or physical processes that alter its chemical composition, mineralogy, and/or texture.

Protolith

The original/parent rock that was altered (metamorphosed).

Foliation/foliated rocks

Characterized by the appearance of a planar arrangement of mineral grains.

Non-foliated rocks

Develop in environments where deformation is minimal and other factors, such as chemically active fluids, play a larger part in alteration.

Depositional environments

Combines chemical, physical, and biological aspects that dictate the type of sediments, rocks, and landforms are deposited or formed.

Erosion

Geological process in which earth material are weathered and transported.

Deposition

The process where earth materials are added to an environment or landform.

Terrestrial environments

Land and water forms, usually involve fresh water.

Mountains

Elevated (more than 2,000 ft) areas of land, usually resulting from tectonic forces.

Deserts

Area receive little rainfall and have high evaporation rates.

Transitional environments

Represent the interface between land and sea, where freshwater meets with seawater.

Marine environments

Found in the open waters, from the shallow depths to the deepest portions of the ocean.

Stratigraphy

A branch of geology that studies rock layers, beds or strata.

Law of superposition

States that if the sequence is undisturbed, the layers on the bottom are the oldest, while the layers above are the youngest.

Law of lateral continuity

States that each stratum extends laterally until it encounters a barrier or obstacle.

Law of original horizontality

States that strata are deposited horizontally.

Law of cross-cutting relationships

States that if a geologic body or discontinuity cuts across strata, it must be younger than the strata it cuts.

Intrusion

An igneous rock body that forms when magma cuts through sedimentary layers and solidifies before it even reaches the surface.

Principle of Faunal Succession

Sedimentary strata contain fossils of plants and animals in a definite, invariable sequence.

Hiatus

The missing time represented by the unconformity in a rock sequence.

Disconformity

Present when there is a missing stratum or strata in the sequence, usually due to a period of non-deposition erosion.

Nonconformity

Occurs when sedimentary strata are deposited on top of igneous or metamorphic rock bodies.

Angular unconformity

When the strata is disturbed by forces that cause folding, tilting, and/or faulting and they no longer appear horizontal.

Relative dating

Uses unconformities to identify the age of strata in relation to other strata, but it cannot identify a stratum's specific age.

Absolute dating

Determining the absolute age of a layer.

Radioisotopic dating / radiometric dating

Isotopes are atoms of an element with different numbers of neutrons, thus with different atomic masses.

14C - 14N (carbon-nitrogen) Dating

Common dating technique used to date fossils that contain carbon in a rock.

Paleontology

The study of fossils linking concepts of geology and biology to understand prehistoric life over geologic time.

Permineralization

When pores and open spaces in tissues are filled with minerals precipitated from mineral-rich solutions, such as groundwater.

Molds and cast

Organisms buried in sediment dissolve or decay away, leaving a hollow space in the organism's shape.

Amber preservation

Organisms that are preserved when they fall into a viscous tree sap which hardens into amber.

Geologic time scale (GTS)

Tool geologists use to classify and date rocks and fossils, where time is divided into eons, eras, periods, epochs, and ages.

Hadean Eon

The formation of the earth; magma ocean, intense bombardment of space bodies.

Archean Eon

Life begins as prokaryotic bacteria, blue-green algae start to produce oxygen in the atmosphere.

Proterozoic Era

Multicellular life emerges.

Cambrian Period

Multicellular life flourishes and diversifies (Cambrian explosion).

Ordovician Period

Age of invertebrates.

Silurian Period

Emergence of plants on land.

Devonian Period

"Age of fishes"; towards the end, true amphibians emerged.

Carboniferous Period

"Age of amphibians".

Triassic Period

Dinosaurs emerged; start of the Age of the Reptiles; first true mammals (therapsids) emerged as well.

Jurassic Period

Dinosaurs dominated earth; then the birds first emerged.

Cretaceous Period

First flowering plant emerged (angiosperms); marked the end of the Age of the Reptiles with the Cretaceous-Tertiary Extinction (K-T Extinction).

Paleogene Period

Start of the age of the mammals.

Neogene Period

Mammals and birds evolved into modern forms; hominids, the ancestors of humans, appeared towards the end.

Quaternary Period

Current period; a cycle of glacial and interglacial periods.

Continental Jigsaw Puzzle

The fitting of the continents together.

Plates or Tectonic Plates

The lithosphere is broken into rigid slabs called tectonic plates.

Convergent boundaries

Sites where plates move towards each other, resulting in a collision or one plate going under the subduction process.

Oceanic-continental plate convergence

Oceanic crust comprises of basalt, making it denser, it subducts underneath the continental crust of the lighter granitic material in the subduction zone

Plate boundaries

Plates' margins always interact with one another, the sites where these margins interact.

Continental volcanic arcs

Partial melting is induced in the overlying continental crust, producing volcanic activity.

Divergent Plate Boundaries

Two plates move apart relative to each other, resulting in the migration of molten material to the surface, generating a new crust.

Continental rift

Divergent boundaries within a continent that generate an elongated depression.

Transform Plate Boundaries

Characterized by two plates sliding past each other, but not destroying or producing new crustal material.