Geology 101

cosmology

The study of the origin and evolution of the Universe.

big bang

The theory that describes the formation of the universe.

13.8 billion years ago

The approximate time when the universe evolved from a high density and high temperature state.

differentiation

The process of formation of Earth’s layers.

core

The dense layer of the Earth composed primarily of iron and nickel.

magnetic field

Created by the presence of liquid metallic elements in the outer core.

magnetic reversals

The periodic switching of the magnetic poles.

mantle

The middle layer of the Earth between the crust and core.

asthenosphere

The plastic (partially molten) layer below the rigid outermost layer of the mantle.

continental and oceanic crust

The two types of Earth's crust.

lithosphere

The outermost rigid layer composed of the crust and upper rigid mantle.

hydrosphere

The sphere comprising the ocean, surface, and ground waters.

atmosphere

The sphere of air composed mainly of nitrogen and oxygen.

Alfred Wegener

Believed to be the father of the theory called plate tectonics.

continental drift

Evidence of the movement of continents, including matched fit, climate belts, and fossil distributions.

seafloor spreading

Evidence that includes the stripped pattern of magnetic field and seafloor ridges.

12

The approximate number of lithospheric plates.

convection currents

The process that drives plate tectonics in the asthenosphere.

divergent plate boundaries

Where plates pull apart, leading to rifting or spreading.

convergent plate boundaries

Result in mountain building.

transform plate boundaries

Where plates slide past one another.

Pangea

The latest supercontinent that started breaking apart around 200 million years ago.

mineral

A naturally occurring, inorganic solid with a specific internal structure.

4,000

The approximate number of known minerals.

5

The number of characteristics a substance must have to be classified as a mineral.

silicates

The majority class of minerals, represented by SiO2.

carbonates

A large class of minerals represented by CaCO3.

anions

Minerals are identified based on their this chemical component.

streak

The color of the powder that a mineral leaves behind.

luster

How light interacts with the surface of a mineral.

hardness

Measured by resistance to abrasion.

specific gravity

The weight of the mineral over the weight of equal water volume.

fracture vs cleavage

The ways in which minerals break.

assemblages

Rocks are made up of these groups of minerals.

three

The number of major types of rocks.

sedimentary

Rocks formed from clasts of pre-existing rocks.

igneous

Rocks formed by solidification from a molten state.

metamorphic

Rocks formed under high heat and pressure resulting in transformation.

texture

Describes the size, shape, and arrangement of grains or crystals in rocks.

rock cycle

An idealized cycle of processes undergone by rocks in the earth's crust.

lava

Molten rock on Earth’s surface.

magma

Molten rock beneath Earth’s surface.

melting

Occurs as a response to changing temperature and pressure.

decompression

Melting that occurs at mid-ocean ridges and rifts.

flux

Melting that occurs above subducting plates.

partial melting

The process that controls the composition of magma.

xenoliths

Chunks of wall rock incorporated into magma.

mafic

Minerals that are rich in iron and magnesium.

buoyant

What allows magma to rise due to its lower density.

viscosity

The measure of a magma's resistance to flow.

sills, dikes, plutons, laccoliths

Different structures formed by solidified magma in various forms.

4

The number of sedimentary rock classes.

weathering

The process that breaks up rock into sediments.

erosion

The removal of grains by agents like water, ice, or wind.

breccia

A clastic sedimentary rock with angular fragments.

conglomerate

Clastic sedimentary rock with rounded pebbles.

sedimentary structures

Features that form during sediment deposition, such as bedding and ripple marks.

paleoenvironment

Sedimentary structures provide insights into this historical environment.

basin

Special places that accumulate sediment.

regression

A sea-level fall that shifts environments toward the basin.

transgression

A sea-level rise that shifts depositional belts landward.

Calcite

CaCO3 in limestone and marble; gives off CO2 (fizzes) in acid

Halite

NaCl rock salt, evaporation of dense brine

Gypsum

CaSO4 . H2O; scratch with fingernail; used in drywall

Pyrite

FeS2 fools gold; cubic crystals main source of sulfur in acid rain, acid mine drainage

Quartz

SiO2; framework silicate, concoidal fracture, harder than glass

Feldspar

most common mineral in earth’s crust; framework silicate, also contains sodium, potassium, calcium; harder than glass

Mica

sheet silicate; perfect cleavage in one direction

Olivine

isolated silicate; density varies with iron and magnesium content

Clay

sheet silicate usually forming tiny crystals; key constituent of mudstone and many soils; may swell when wetted

glass

(non-mineral) has no ordered crystal lattice (a chaos of ions); made by quenching a melt (no time to form lattice)