Geology - Exam 2 Study Guide

Earth System

The interconnected physical, chemical, and biological processes that shape Earth over geologic time.

Geology

The study of Earth's history, structure, composition, and processes.

Rock Record

The archive of Earth's history preserved in exposed and buried rocks.

Plate Tectonic Theory

The theory that Earth's outer shell is divided into several plates that glide over the mantle.

Uniformitarianism

The principle that the same natural laws and processes observed today have always operated in the past.

Actualism

The concept that the laws of nature are consistent and have not changed over time.

Igneous Rock

Rock formed from the cooling and solidification of magma.

Rock Outcrop

Exposed rocky surfaces at Earth's surface, accessible for study.

Extrusive Igneous Rock

Igneous rock formed from magma that solidifies at the Earth's surface after being erupted.

Weathering

The collective term for chemical and physical processes that break down rocks at the Earth's surface.

Erosion

The collective term for processes that move rock away from an outcrop at the Earth's surface.

Stratum

A layer of sedimentary rock deposited in a discrete episode of geologic time.

Lithification

The process of compression or cementation that binds sediment grains together to form sedimentary rock.

Metamorphic Rock

Rock formed by the physical or chemical alteration of pre-existing rocks under high temperatures and pressure.

Rock Cycle

The process showing the transformation of rocks between igneous, sedimentary, and metamorphic types over geologic time.

Principle of Stratigraphic Superposition

The principle stating that the oldest strata are at the bottom in an undisturbed sequence of strata.

Oceanic crust

The Earth's crust that underlies the ocean basins, primarily composed of mafic igneous rocks with a density of approximately 3.0 g/cm3.

Continental crust

The Earth's crust that forms the continents, primarily composed of felsic igneous rocks with a density of approximately 2.7 g/cm3.

Mohorovicic Discontinuity

Also known as the Moho Discontinuity, it is the boundary between the Earth's crust and mantle, located between 5 and 60 km below the surface, marked by a change in the velocity of seismic waves.

Lithosphere

The rigid outer layer of the Earth, consisting of the crust and upper mantle.

Plate Tectonics Theory

A scientific theory explaining the movement of the Earth's lithospheric plates, involving the formation of new oceanic crust, subduction zones, earthquakes, and volcanic activity.

Plate Tectonics

The scientific theory that Earth's lithosphere is divided into large plates that move and interact with each other, leading to various geological phenomena.

Subduction Zones

Areas where one tectonic plate is forced beneath another into the mantle, often leading to volcanic activity and earthquakes.

Lithosphere

The rigid outer layer of Earth, including the crust and upper mantle, divided into tectonic plates.

Asthenosphere

The semi-fluid layer of the upper mantle on which the lithospheric plates float and move.

Plate Movements

The horizontal and vertical motions of tectonic plates caused by forces such as mantle convection, leading to various geological features and events.

Harry Hess

An American geologist known for his contributions to the theory of plate tectonics, particularly for his work on sea-floor spreading and the concept of mid-ocean ridges.

Mid-Ocean Ridge Model

Proposed by Hess, it explains the rise of hot mantle material to the lithosphere, formation of new ocean crust, lower seismic wave velocity due to heat transfer, elevation of the ridge, and the separation and lateral flow of new crust.

Guyots

Flat-topped seamounts in the Pacific Ocean discovered by Hess, eroded by waves at sea level, and named after a geographer.

Subduction Zones

Areas where oceanic crust is "swallowed up" at deep-sea trenches, explaining low-density rock observations and the existence of trenches.

Delta Front

Deposits of a delta that lie directly above deposits of the prodelta as the delta progrades, with marine fauna and flora, while the prodelta consists of clays and is formed at a lower angle.

Carbon-14

Unstable carbon isotope with different atomic weights due to varying numbers of protons and neutrons in the nucleus.

Porous Skeletons

Mutation in modern hexacorals allowing them to quickly crowd out competitors by requiring less calcium carbonate to grow and colonize large areas.

Cementation

The most important chemical process of lithification involving the precipitation of mineral matter in pore spaces between sediment grains to form solid rock.

Fossil Succession

Principle stating fossils occur in a consistent order in rock layers, allowing geologists to correlate and date rock sequences based on specific fossil assemblages, providing a relative timeline of Earth's history.

Guyot

Submerged, extinct volcano with a flat top, also known as a tablemount or undersea mountain.

Guyot

A flat-topped seamount formed by the erosion of a volcanic island and subsequent subsidence.

Permineralization

The process of infilling tissues with inorganic materials, often fine quartz, which can help preserve soft tissues and create fossilized remains.

Kingdom of Animals

Includes organisms like Sponges, Cnidarians, Lophotrochozoans, Edysozoans, and Deuterostomes.

Earth System

Comprises the biological component (diverse forms of life) and the physiochemical component (inorganic physical/chemical processes and their products) that are interrelated.

Fossil Plants

Can be used to reconstruct past climatic conditions as they reflect ancient climatic conditions due to their sensitivity to climate.

Point Bar

Meandering river sediments that accumulate on the inside bend of a river.

Abyssal Clay

The dominant sediment on the sea floor below depths of 4000 m, typically fine-grained clay particles settled from the water column above.

Guide fossils

Fossils used to determine the relative age of rock layers based on their widespread distribution and easy recognition, aiding in correlating different rock units. They do not provide specific numerical ages for rocks.

Radiocarbon dating

A method using the decay of Carbon-14 to Nitrogen-14 to date organic remains, with a half-life of 5730 years, applicable to recently deceased organisms.

Predation

A factor limiting the presence of certain species in an environment by preying on them, affecting population size and distribution.

Unique factors for life on Earth

Earth's distance from the sun, mass and gravity retaining water and gases, and small size reducing meteorite impacts, enabling the existence of life.

Adaptive radiation

Rapid evolutionary expansion of one or more groups of organisms into new ecological niches, leading to species diversification.

Biogeographic scale

Mammoths did not occupy similar climate belts in North America due to unsuitable climate conditions for their adaptation to cold environments.

Sedimentary Environments

The locations where sedimentary rocks are formed, providing clues about past environments.

Ecology

The study of the distribution and abundance of organisms in their natural habitats.

Paleontology

The study of ancient life forms.

Sedimentology and Stratigraphy

The study of ancient environments based on sedimentary rocks and their layering.

Paleo-environmental Reconstruction

The process of reconstructing ancient environments using geological evidence and the concept of actualism.

Savannahs

Areas with sufficient rainfall for grasses to grow but not enough for forests, often home to large grazers and carnivores.

Grasslands

Regions where grasses thrive due to adequate rainfall, preventing the growth of forests.

Temperate Forests

Areas characterized by abundant deciduous trees like maple, oak, and beech.

Evergreen Forests

Forests found poleward of temperate forests, with conifers like spruce, pine, and fir that retain needles year-round.

Tundra

High latitude regions with cold conditions year-round, featuring a permanently frozen soil layer and specific plant and animal ecosystems.

Drainage System

Network of small streams merging to form perennial rivers like the Mississippi and Amazon that drain into large bodies of water.

Braided Rivers

Rivers with multiple branching and merging channels, depositing sediment in moist regions.

Playa Lake

Temporary lakes formed in desert regions due to sufficient rainfall, often leading to the precipitation of evaporite minerals.

Glaciers

Masses of ice that transport eroded sediment, leaving striations on the bedrock and forming features like till, moraines, and varves.

Varves

Annual deposits in proglacial lakes, with alternating layers of sand and silt/clay representing seasonal variations in sedimentation.

Bacteria

Microorganisms that transform dead matter into compounds of nitrogen and phosphorus.

Nitrogen and Phosphorus

Important nutrients for phytoplankton, brought to the surface waters in upwelling zones.

Phytoplankton

Small plant-like protists such as diatoms and cyanobacteria that drift in the photic zone.