Geology Midterm Study Guide

Topics: Sedimentary rock, Igneous rock, Rock Pages: 6 (770 words) Published: October 28, 2013
Review for Midterm
Earth is 4.6 billion years old

What do Geologist do
Study the structure of mountain ranges
Attempt to predict geological hazard
Principle of parsimony = Occams Razor (Simpler is better)

Deep Time
The amount of time of Earth’s existence
Universe began=Big Bang Theory
Earth’s creation= Nebula hypothesis
Geological time Scale
Largest units to smallest (EEPE)
Eons
Eras
Periods
Epocs
Cambrien Explosion
Mass amount of fossils found in the Cambrien time period
Names come from location
Precambria
88.1% of the geological time scale
Geologic Range
The existence of an organism
Methods of dating rocks
Absolute Age dating (1896)
Half lives. Jangus you know this
Relative Age dating
You know this too gumbus

Plate Tectonics
Lithosphere is divided into plates
7 large plates
20 smaller plates
Rigid lithosphere
Rest on the asthenosphere (the easily deformed or partially molten part of mantle below the lithosphere Plates move 3-5 cm/year
How do they move?
Convectional flow
Circular movement in the asthenosphere
Hot material rising cool sinking
3 Ways
Divergent
Plates move apart from one another
Convergent
Plates move toward another
Transform
Two plates slide past one another.

Evolution

Modern Organisms
Vestigial organs
“tail bone”
Organic Evolution
The study of fossils in geology
Early Interpretation of Fossils
Herodotus (450 B.C.)
Found seashells in sedimentary rocks.
Sea level must have dropped
Fossils
Forms
Rapid burial
Sediment to prevent destruction of the dead organism by scavenging or bacterial decay Fossil Types
Freezing
Desiccation/Mummification
Preservation in tar
Preservation in peat bogs
Carbonized imprints in fine-grained sediment
Three Major rock types
Igneous
Fire rocks
Metamorphic
Change rock by heat and pressure
Sedimentary
From sediment
Three types
Clastic
Biologic
Chemical

Sedimentary:
Formed from pre-existing rocks or pieces of once-living organisms. Formed from deposits that accumulates on the Earth’s surface. Distinctive layering or bedding
Forms by
Weathering -> transported to basin or depression -> cementation Clastic Sedimentary Rocks
Made up of pieces (clast) of pre-existing rocks.
Range from pebbles to boulders
Shale=clay, siltstone=silt, sandstone=stone
Smallest grains:
Clay
Silt
Sand
Biologic sedimentary rock
Large numbers of living things die, pile up, and are compressed and cemented to form rock. Carbon-rich plant -> coal
Chemical sedimentary rock
Chemical precipitation
Igneous:
Felsic/granitic: Silica rich, typically related to continental or land crust Intermediate/andesitic: commonly associated with convergent plate boundaries along the rim of the Pacific Mafic: Silica poor, usually related to the oceanic crust

Form:
When molten rock (magma) originating from deep within the Earth solidifies. The chemical composition of the magma and its cooling rate determine the final igneous rock type. Intrusive (plutonic)
Extrusive (volcanic)
Solidifies deep beneath the Earth
Solidifies near the surface
Magma solidifies slowly
Solidifies quickly
Grow large size, coarse
Tiny, fine grained

Metamorphic:
Form when rocks are subjected to high heat, heat pressure, hot, mineral-rich fluids or, more commonly, some combination of these factors. Found deep within the Earth. Often squished, smeared out, and folded.

Foilated metamorphic rock
Pressure squeezes the flat or elongate minerals within a rock so they become aligned. Develop a platy or sheet-like structure that reflects the direction that pressure was applied in. Non-Foilated metamorphic rock

Forms when hot igneous rocks intrude some pre-existing rock. Does not have a okaty or sheet like structure

-the type of statistics used for measuring sorting   
Grain size (mm)
(Absolute value) = grain size – mean
Easy shit

-the percent of geologic time of eons (Precambrain vs. cambrain) The Precambrian Eon begins 4.55 billion years...
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