Geology 50 Questions and Answers

Practice vocabulary flashcards covering fundamental geology concepts, rocks, minerals, geological processes, hydrology, and mass wasting.

Earth's Interior Heat

The condition where rock deep within the Earth is hot and heat flows out toward Earth's surface.

Mantle

The most voluminous of the Earth's three major concentric zones.

Mineral

A material that is solid, occurs naturally, has a crystalline structure, and has a definite chemical composition.

Oxygen and Silicon

The two most abundant elements located in Earth's crust.

Xenoliths

Fragments of country rock that are distinct from the body of igneous rocks in which they are enclosed.

Extrusive Igneous Rock

Fine-grained igneous rocks with grains $< 1.0\,\text{mm}$ that have small grains and cooled rapidly.

Shield Volcano

A volcano characterized by broad bases and gently inclined slopes.

Composite Volcano

A volcano composed of alternating layers of pyroclastic fragments and solidified lava flows.

Ferromagnesian Minerals

Minerals such as pyroxene, amphibole, biotite, and olivine that are chemically altered in the presence of oxygen.

Dissolved Carbon Dioxide

The most important natural source for the formation of acid responsible for rock weathering at the Earth's surface.

Sedimentary Grain Sizes

The classification of sedimentary grains in order of decreasing size: gravel, sand, silt, and clay.

Silt

A sedimentary particle size composed mostly of quartz grains.

Well-Sorted Sediment

Sediment in which the grains are nearly all the same size.

Bedding

A term that describes a series of visible layers in sedimentary rock.

Lithification

The general term for the processes that convert loose sediment into sedimentary rock.

Detrital Sedimentary Rocks

The most common type of sedimentary rocks.

Coal

An organic rock formed from the compression and alteration of plant remains such as leaves, twigs, and tree trunks.

Confining Pressure

Pressure applied equally to all surfaces of a substance as a result of burial or submergence.

Metamorphic Rock Factors

The four critical factors controlling the characteristics of metamorphic rocks: composition of the parent rock, temperature, pressure, and water.

Metamorphism

A rock alteration process that may involve changes in texture and composition, but does not involve complete melting of the rock.

Slate

A metamorphic rock that splits easily into thin flat sheets, commonly used for making chalkboards, pool tables, and roofs.

Metasomatism

Metamorphism coupled with the introduction of ions (charged atoms) from an external source.

Contact Metamorphism

Metamorphism that occurs adjacent to a pluton when a body of magma intrudes a relatively cool country rock.

Quartzite

One of the two most common non-foliated metamorphic rocks, alongside marble.

Age of the Earth

The approximate age of the Earth, established at $4,500,000,000$ to $4,600,000,000\,\text{years}$.

Correlation

In geology, the process of determining the time equivalency of rock units.

Uniformitarianism

The principle that states the same processes and natural laws that operated in the past are those we can observe or infer from observation as operating at present.

Mesozoic Era

The geological era whose close was marked by the extinction of dinosaurs.

Lateral Continuity

The principle stating that an original sedimentary layer extends laterally until it tapers or thins at its edges.

Precambrian

The vast span of geological time that precedes the Paleozoic Era.

Paleozoic Era

The geological era that began with the appearance of complex life, as indicated by fossils like trilobites.

Shear Strength

The resistance to movement or deformation of soil.

Rotational Slide

A mass movement involving motion along a curved surface.

Flow Terms Velocity Sequence

Mass movement flows listed in order of decreasing velocity: debris avalanche, mudflow, earthflow, and creep.

Earthquakes

Geological events that commonly trigger mass wasting events.

Permafrost

Ground that remains frozen continuously for many years.

Soil Creep Factors

Two factors contributing significantly to soil creep: water in the soil and freeze-thaw cycles.

Gravel Bed Load Movement

The method by which the gravel bed load of a stream moves, specifically by sliding and rolling.

Hydrologic Cycle

The visual concept representing the movement and interchange of water between the sea, air, and land.

Stream Lengthening

The processes through which a stream can increase its length: building a delta, meandering, and headward erosion.

Martian River Channels

Features identified on the planet Mars that resemble river channels on Earth.

100-Year Flood

A flood event that has a $1\%$ chance of occurring in any given year.

Oxbow Lake

A crescent-shaped lake formed when a meander is cut off from a stream.

Aquitard

A rock or sediment body (such as shale) that retards the flow of ground water.

Spring

A place where water flows naturally from rocks onto the ground surface.

Impermeable Rock

A rock that does not allow water to flow through it easily.

Confined Aquifer

An aquifer completely filled with water under pressure and separated from the surface by an aquitard.

Geyser

A type of hot spring that periodically erupts hot water and steam.

Cone of Depression

A depression that often develops in the water table when water is pumped out of an unconfined aquifer through a well.

Aquifer

A body of saturated rock or sediment through which water can move easily.