4.8 billion years ago

center: sun

planetary accretion: things that have mass tend to be attracted to one another

extremely hot- radioactive material in core: sheds heat outward to earth's surface

no oceans

no atomosphere

1. impact- no atmosphere to burn these et bodies impact created energy (heat)

2. gravitational compression (packiing in would have heated up)

3. radioactive decay- not done doing this

oceans

atmosphre

internally differentiated

went from homogenous to varied earth

completed about 4.0 billion years ago

N2, CO2, CH4 (came from hot temp)

-O2 not there (no respiration)

early 1950s

didn't have much in way of env problems

not a lot of measurable human impact

collectively have started to have measurable impact

major cause of env impact

hunter gather > industrial society (env impact)

bicycles have impact

all comes at price= impact on env

enjoyment of this standard of living has an impact most are not aware of 

-dont have to be opposing

-one based on scientific method

-one based on theologic system of beliefs

-science vs theology (none more right than other)

1. formulate a testable falsifiable hypothesis

2. design experiments

3. collect data

4. evaluate

5. accept/reject hypothesis

volcanic eruptions

huge endowment of gases

amount of volcanis is fading but ongoing

4.85 bil years ago a lot of this 

H20, CO2, CH4, SO2

these gases dispersed into atmosphere

since we only live decades, we think earth is non changing but its changing on a geologic time scale

earth is very dynamic, continents in motion (cm a year)

form via the cooling and crystallization of molten rock 

no open spaces, single crystals

form when we subject some preexisting rock to elevated pressure and temperature

(started as sandstone, subject to pressure, depth, 30 million years- then black and red with gems)

law of superposition

law of original horizontality

principle of cross cutting relations

principle of inclusion

principle of faunal succession

in a sequence of undisturbed sedimentary rocks, the oldest rock is on the bottom

-proposed by Steno in 1600s

sediments are deposited in a flat lying manner; a sequence of sedimentary rocks that is not horizontal has been disturbed

-a tectonic event caused sloped rocks

the present is the key to the past

by making observations about current nature of world- we can infer about geologic time in past

the amount of time it takes for 1/2 the material to undergo radioactive decay

parent - half life- daughter

-know ratio of parent/daughter

-know half life

protons (+)

neutrons (neutral)

electrons (-)

# of protons + neutrons determinse atomic mass

 # of p= atomic number

# of e- determines electrical behavior

number of neutrons varies within atoms

C12, C13 ARE STABLE

C14- unstable- spontaneous nuclear decay

 composition- slippery

internal strucutre- hard,soft

isochemical- carbon strong in all directons

isostructural- cubically stacked

1. color- have to be careful, rocks arent always same color

2. cleavage- tendency to break along planes of weakness

3. hardness

4. density- those higher on periodic table have lower density

5. luster- metallic glassy

metal + O 

Fe₂O₃

metal + Si + O

SiO₂

metal + S

PbS (galena)
FeS₂ (pyrite) 

molten rock beneath Earth's surface

crystllize beneath Earth's surface- plutonic igneous rock

magma goes up due to less density

molten rock on Earth's surface

crystallize on surface (volanic extrusive)

material is now less dense 

when water freezes it becomes less dense

as magma ascense, magma starts to cool and becomes denser then may or may not shoot all way to surfae and then crystallizes

cool slowly (100,000s- mils years)

crystals grow large (have time to grow)

phaneritic texture

cool rapidly (hrs-day)

crystals are very small

apharitic 

cools slowly - - ascends quickly -- remaining liquid cools rapidly creating smaller/finer crystals + grains

low iron and magnesium (Fe + Mg)

hi Silicon

light colored

dark colored

lots of Fe/ Mg

less Silicon

almost all magma at inception are mafic

left side:quartz

k-feldspar

biotite

right side: olivine 

pyroxene

plagiodase feldspar

predicts cooling stages of magma

continuous (no fixed compostion)

Hi Temp: 1000 Cent Ca-plagioclase feld -------> Low Temp 650 Cent- Na-plagioclase feld

Discontinous (discrete mineral phases)

Hi Temp: Olivine --> Pyroxene --> Amphibole --> Low Temp Quartz, Potassium Feldspar, Biotite

ones closer to bottom of series are more resistant to dissolving and more tenacious and tough than ones higher on list

quartz more chemically stable at surface temperature

angular (jagged) -----> more and more rounded with transportation

large -----> small

diversity of minerals -----> less diverse feldspar, quartz dissolves

form from grains getting cemented together

grain size helps determine name of mineral

shales- tiny grains

siltstone- slightly larger

sandstone- more large

conglomerate- really large

poorly rounded- immature

well rounded- mature

large- immature

smaller- textually mature

lots of minerals- compositionally immature

quartz- comp mature

dissolve in hot- can no longer dissolve more into it

michigan basin- lake acts as trap and collects fine particles/ mud at bottom due to lake's low energy

evaporites- salt deposit

limestone- calcite ppt   CaCO₃

Rockies Mts

farily large rocks-angular-congomelatic

form via increased pressure and/or temperature; no melting involved

happends due to colliding plates- rocks on surface

plate boundaries where plates collide

mechanical changes

-deformation

-recrystallization

-occur at low to high metamorphic grade

-characteristic of all types of metamorphism

-minor to major

-occur at intermediate to high metamorphic grade

-dont grow new ones until P + T get elevated

-directed stress/ directed force

preferential grain alignment

SHALE- grains begin to align

SANDSTONE- in response to pressure, contact pts weld together- recrystallization

-mineral stability 

-what minerals are then (on p vs t chart) at any given point is determined where boundaries are between materials

gemis in rocks grow in response to metamorphic P+T

what you started with determines what you end up with

contact and

regional

type of metamorphism

occurs when Temp increases

ex: igneous intrusions

local effect around igneous intrusions (no more than 1 km)

occurs when P/T increase

App Mts- formed when NA collided with Africa 100 million years ago

low: shale -----> slate -----> sandstone -----> quartzite ---->medium grade new minerals- shist ------> gneiss high 

upper limit of high p/t- conditions right before melting would occur

climatologist 1800's

fit of continents, fossil distribution, evidence for glaciation

no mechanism to explain how continents moved

pangea

faunals would have difficult time evolving separately meant likelihood that east coast of SA and west coast of Africa mezosaurs evolved together 

must have been assembled at some point

-above dashed line; contains all of crust too

- elastic material

-brittle

-no solid piece, broken into smaller plates

-plastic

-flowing

-substantially hotter

-more pressure

lighter, buoyant (lower density material), thicker

intermed-felsic

-resuggested concept of continental drift

-WWII drove boat for US navy mapping ocean floor so subs wouldnt crash

-mapped topography of sea floor

-sea floor spreading

-argued there were big,deep trenches in certain spot- subduction

mid ocean ridges gurdle entire globe; continuous

Hess found basalt of sea floor

creating new oceanic crust at MOR which serves as force to push plates away from MOR

older rocks are progressively farther away from middle of MOR

consuming oceaning crust somewhere

-Hess aruges asthenosphere is circulating and convecting

oldest oceanic crust 180 mil years

reinforces concept of sea floor spreading

composition of seafloor- iron rich

when basalt erupts -> crystals form, sense Earth's magnetic field

-Earth's magnetic field is unstable- flip flops frequently

-magnetic north pole wanders around on short time scale

-compasses could point south

-magnetic field 10% weaked in last few decades

-geograph NP and magnetic NP differ

-as we move away from MOR, mirror images reflect magnetic field reversals (parallel)

-looked at Wegner, Hess seafloor spreading, age dating, etc...

proposed plate techtonics- continents move about th earth---> unified theory of geology

-weak seismicity- not perceptual to humans

-weak magma movement

-Red Sea and Gulf of Aden now have oceanic crust erupting from MORs

-East African Rift is still in a continental setting and may fail in the future forming an aulocogen (failed 3rd arms)

-1 rift suceeds, 1 rift fails

oceanic or continental crust --> focus heat crustal thinning extend

Basalt eruptions- mantle composed of basalt

ocean setting: MOR

continental setting: Rifts

      ---->

                                    <-----      relative plate motion

no igneous activity

strong shallow seismicity

oceanic: erupting basalt, no volcanic activity, note offset nature of MOR

earthquakes

San Andres Fault

----> <----- relative plate motion

A. continent-ocean: abundant plutonism/volcanism

seismicity: strong, shallow to deep

B. oceanic-oceanic: either can be subducted

C. continent- continent: neither subducts

no igneous activity

shallow to moderately deep seismisity

mantle convection

ridge push-slab pull

mantle material will come up to point beneath crust 

hot spots: fixed mantle plumes