GEOL101 Exam 1

Def of Geology

science of understanding our planet

Xenophanes

First geologist

greek philosopher discovered seashell imprints on a mountain

Catastrophism

surface of Earth shaped by extreme events

Uniformitarianism

physical, chemical, and biologic laws are uniform throughout Earth’s history

1815 Map of Great Britain

map that changed the world

showed coal locations

Principles of Geology

published by Charles Lyell

birth of modern geology

popularized uniformitarianism

Nebular Theory

bodies of our solar system evolved from enormous rotating cloud called solar nebula after big bang

Accretionary disk

During collapse the nebula

evolves from huge rotating cloud to smaller fast spinning disc

protosun (presun)

formed through collisions and other interactions gases and particles

matter condensing at center

Hadean eon

1. Earth forms

Archean eon

2. earliest evidence of life; microbial earth

Proterzoic eon

3. oxygen begins accumulating in atmo; earth grow cold; oxygenation and snowball earth

Precambrian

Hadean, Archean, Proterzoic

Paleozoic

4. complex animal life becomes abundant in fossil record; cambrian explosion

Mesozoic era

5. age of dinosaurs

Cenozoic era

6. mammals diversify; mammals and humans

Phanerozoic

Paleozoic, Mesozoic, Cenozoic

Earth internal structure by composition

Core, Mantle, Crust

Inner core

iron and nickel

solid by gravitational attraction despite high temp

Outer core

liquid

iron and nickel but less gravitational attraction

Mantle

many elements and minerals

not molten and not brittle

solid but ductile

Upper mantle elements

Olivine, Si

Lower mantle

Fe, Mg, Si; heavier elements

Crust

solid and brittle

rocky material less dense than mantle

Oceanic crust

8 km thick

composed of basalt

denser crust

Continental crust

45 km thick

composition of granite

less dense crust

P waves

travels through earths interior w compression movements (squeezes rock)

travels all the way through Earth

S waves

slow moving

shears rock (up and down movements)

bounces off liquid outer core

Earth internal structure by physical properties

Lithosphere, Asthenosphere, Mesosphere

Lithosphere

rigid layer that includes crust and upper mantle

strength is function of temp and pressure

Asthenosphere

region of mantle where rocks are ductile

Mesosphere

lower mantle; solid with high strength

Geosphere

what geological events shaped the planet

Bathymetry

Topology underwater

Oceanic continental shelf

submerged, gently sloping edge of continent

extends from the coastline out to sharp drop-off called the shelf break

Abyssal plains

middle of pacific ocean

no sediment from continents

flat and smooth

Ocean trench

off the coast of Japan

where marianna trench is

very deep

Ocean ridge

Indian Ocean

fractured region of oceanic crust

Canadian shield

expansive region of ancient precambrian rocks

Alfred Wegner

proposed continental drift

proof of continental drift

The continents kinda fit together + overlapping continental shelves

Different fossils of extinct plants and animals are found on different continents today

Some mountain belts (ex: appalachian NA and caledonian EU/AF) appear to be very similar and line up

Glacial carving (large chunks of ice scoops across rocks and leaves smoothed streaks)

opposition to continental drift

lack of concrete mechanism of how continental drift happened

Tectonic plates physical property

rigid lithosphere on top of asthenosphere

Plate boundaries

where tectonic plates meet

Proof of plate boundaries

concentrations of earthquakes, volcanoes, and other dynamic phenomena

interior of plates are almost earthquake free

Divergent

magma rises up through lithosphere and lifts up / spreads lithosphere

spreading continues and creates a rift valley

creates oceanic crust in ocean basin

Oceanic-continental Convergent

Oceanic higher density sinks (subduction) and heats up

Leads to melting and volcanos

new mountain ranges

Oceanic-oceanic Convergent

less dense subducts and creates a chain of volcanic islands (volcanic island arc)

Continental-continental Convergent

Neither plates want to be subducted → crust goes upwards

Creates large mountain ranges; earthquakes but no volcanoes

Transform

Plates slide past each other in horizontal motion

Still has earthquakes but no generation of land bc no subduction

Earthquake depth

Subduction in direction from surface level earthquakes → deeper earthquakes

Subducting plate sinks into mantle

Hot spots

Hawaii

plate moves on top of hot spot which doesn’t move

see direction of plate movement

Mantle convection

Drives plate tectonics

Hot less dense material in mantle slowly rises and creates divergence

Cooling of the mantle causes it to sink back down, taking lithosphere with it

Minerals

Crystalline building blocks of earth

requirements to be mineral

1. naturally occurring

2. inorganic (no carbon/water bonds)

3. solid under conditionals where it occurs

4. ordered internal structure

5. defined chemical composition or compositional range

Rock

naturally occurring aggregate of mineral grains

Identify mineral physical properties

color/streak

hardness

cleavage or fracture

luster and crystal form

specific gravity and special properties

mineral color/streak

Scratch mineral on white ceramic plate to observe powderized version

Color and streak ^ can be diff (oxidizing)

color/streak example

Hematite
silver/red

Mohs hardness

relative scale with unequal intervals

Lower hardness will not allow to damage higher hardness

mohs hardness diamond

10

mohs hardness quartz

7

mohs hardness graphic

1-2

mohs hardness steel file

6.5

mohs hardness glass

5.5

mohs hardness fluorite

4

mohs harness iron nail

4.5

mohs hardness copper coin

3

mohs hardness fingernail

2.5

mohs hardness talc

1

Cleavage

repeated flat surfaces following planes of weaker bonding

Fracture

shatters in random directions

Luster

reflected light

Crystal form

shape of formation

crystal form of pyrite

cubes

Specific gravity

compares density with water

special properties

chemical reactions

fluorescence

odor

magnetism

mineral-forming processes

Crystallization from cooling melt

Precipitation from water

Biological mineral formation

Mineral recycling

Deposition from volcanic gases

Elements in continental crust

O and Si 74.3% of crust by weight
creates SiO₄ silicate tetrahedron

Independent tetrahedrons

Olivine, garnet

No cleavage

Single chain

Pyroxene

cleavage near 90 degrees

Double chain: one line of honeycomb

Amphibole

Cleavages near 60 and 120 degrees

Sheet structure: honeycomb like

Brittle

Micas clay minerals

Micas split in one perfect direction

Three-dimensional framework

Strong minerals

Quartz

Fractures

Minerals in crust

Feldspars 51%

quartz 12%

Mafic

dark silicates because of Fe and Mg

darker and denser

Silica poor (45-52% SiO₂)

thin runny magma made of mantle

ex: basalt

Felsic

light silicates

lighter and less dense

Rich in silica (66-76% SiO₂)

thick magma mixed with continental crust material

Al; Ke; Na; Si; O

Ex: granite

Magma

Completely or partially molten rock at depth

Parent material of igneous rocks

Formed by partial melting of the crust

Lava

magma that has surfaced

components of magma

Liquid portion = melt

Solids: crystals of silicate minerals

Volatiles: dissolved gases in melt that vaporize at surface pressure

• Water vapor (H₂O)

• Carbon dioxide (CO₂)

• Sulfur dioxide (SO₂)

Crystallization

cooling of magma which results in systematic arrangement of ions into orderly patterns

SI and O atoms link first to form tetrahedra

more tetrahedra and other ions join together as heat dissipates

extrusive igneous rocks

fast cooling at the surface

Fine grain (aphanitic)

intrusive igneous rocks

also called plutonic

Observed at surface following periods of uplifting and erosion of overlaying rocks

Chunky (phaneritic)

Intermediate

Between felsic and mafic

Moderate amt of silica (52-66% SiO2)

Contains at least 25% of dark silicate minerals

Intermediate in color (gray or salt and pepper)

ex: andesite

Ultramfic

ex olivine, pyroxene

Rare; from upper mantle

Extremely low Si (38-45% SiO2)

Extremely high Fe and Mg

Very dense

Dark green color

Bowen’s reaction series

specific order in which different minerals crystallize from cooling magma

ultramafic > mafic > intermediate > felsic

Ultramatic and basalt: least stable; weathers fastest

Andesitic and granitic: most stable; weathers slowest

Fractional crystallization

1. early forming olivine crystals float to surface from mafic magma

2. loss of olivine makes the magma more felsic

3. less dense felsic makes crystals fall to the bottom of the magma

4. crystals remelt in lower portion of magma

5. lower magma mafic while upper felsic

Acid rain

Chemical weathering

H₂O and CO₂ produced

The reactant effervesces

positive feedback loop

CO₂ production leads to more acid rain and more chemical weathering

specific weight of galena

heavy due to Pb in composition