GEOL 101 Exam 2 Review

Sedimentary Rock

Rock that forms by cementing together of fragments, broken off, pre-existing rock, or by the precipitation of mineral crystals out of water solutions at or near the earth surface.

Clasts

Can be the broken down bits of a rock. Can be a mineral that wasn’t created but it was eroded out, broken out, or weathered out and now its loose clast.

Chemical weathering

Chemical reactions of minerals in rocks to air or water.

Clastic sedimentary rocks

consists of mineral grains, rock fragments, and cementing material.

Grain size

the diameter of individual grains of sediment or lithified particles in clastic rocks.

Chemical sedimentary rocks

produced by inorganic precipitation of dissolved compounds (example:through oversaturation or evaporation).

Foliation

a planar fabric that cuts through the rock due to alignment of platy minerals and can lead to alternating light/dark bands.

Metamorphism

are those that have undergone solid-state diffusion of pre-existing rocks.

Protoliths

pre-existing rocks that are altered during metamorphism.

Metamorphic grade

a measure of the intensity of temperature and pressure conditions that lead to alteration.

Contact/thermal metamorphism

Low pressure, high temperature metamorphic setting.

Differential stress

stress that is greater in ONE direction.

Paleontology

the study of fossils.

Fossilization modes

types of preservation and how preservation takes place.

Evolution

the gradual change of physical traits of organisms through time.

Mass extinctions

global, abrupt decreases in biodiversity.

Geologic time scale

Precambrian → Paleozoic → Mesozoic → Cenozoic → Anthropocene

Uniformitarianism

processes observed today are the same as what has occurred through Earth’s history.

Unconformities

Gaps in the rock record from nondeposition or erosion.

Angular unconformity

Underlying layers are tilted.

Nonconformity

Underlying layers are igneous or metamorphic rocks, not tilted.

Disconformity

Underlying layers are sedimentary, not tilted.

Absolute dating

Determines specific age using parent isotopes decaying to daughter isotopes.

Isotopes

Elements with varying neutrons.

Half life

Time for half of unstable nuclei to decay.

Stratigraphic columns

Depict strata in a region, representing different rock types.

Cross-cutting intrusions

Younger features cutting across older features.

Watersheds

Areas draining into a river or lake.

Base level

Lowest point a stream can erode, local (lake) or ultimate (sea level).

Stream capacity

Total sediment a stream can carry, dissolved, suspended, and bed loads.

Braiding streams

Choked channels with high stream capacity, meandering streams with looping channels.

Recurrence intervals

Probability of an event happening in a given year.

Groundwater basics

Study of groundwater, filling pore spaces in rock.

Porosity

Total volume of open space in rock.

Permeability

Degree of material allowing fluid flow.

Aquifer

Rock holding and transferring water, confined or unconfined.

Water table

Top of groundwater reservoir, separating saturated and unsaturated zones.

Potentiometric surface

Analog of water table for confined aquifer.

Groundwater issues

Contamination, cone of depression, groundwater mining.