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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.
