the laws of nature haven't changed over the course of time

the present is the key to the past

*James Hutton- applied principle of unif. to studying rocks to prove that horizontal rocks are on top and vertical below

the study of layered rocks

1. Oldest Strata is on the bottom

2. principle of original horizontality- sedimentary rocks are deposited FLAT

3. principle of original lateral continuity- similar rocks on opposite sides of a river are connected 

contact area where erosion takes place, represents time of erosion rather than deposition

1. Angular Unconformity

2. Unconformity Disconformity

3. Nonconformity

a group of tilted & eroded rocks, younger rocks on top

irregular surface between bed reveals erosion,

both layers are sedimentary (can be diff. types)

sequence of events oldest to youngest

only know the sequence not the time in between

specific dates, begin & end

uses radiometric dating

reveals anatomy

hard parts-teeth and bones commonly preserved 

soft parts (rare)- tissue, must be rapid burial in anoxic environment

Monument Valley Stratigraphy 

(rock type & deposition environments)

bottom layer: shale - river deposits

middle: sandstone - ancient sand dunes

top: conglomerate- braided stream, unconformity- mountains rising & rain

13.7 billion years ago

universe was in a hot, dense state

Elements: 

Inside- close to sun so Hydrogen doesn't form, IRON does & gas is pushed out (terrestrial planets)

Outside- COLD, hydrogen condenses, so gasey planets

4.6-3.8 BYA- Precambrian Period

start of Earth's history (4.6 BYA)

segregation of core, mantle & crust

no rocks survived, very hot, volcanic outgassing 

Earth condenses from DEBRIS

meteorites & comets bombard planet

formation of our solar system

ingredients: metals, rocks, light gases = the snow line

a Mars- sized object slammed into Earth and created debris that went through dust bunny process & resulted in Moon

moon froze

4.4 BYA 

start of electromagnetic protection

volcanic (degassing from interior) --> water vapor

ability to reproduce, have a membrane, USES ENERGY, mutation (mistakes are crucial)

Requirements: energy, organic molecules, liquid water

components of life: amino acids, nucleic acids, RNA, DNA

formed the 12 most common amino acids

3.5 BYA - stromatolite

blue green algae trapped layers of sediment

prokaryote able to photosynthesize

Indicates: Methane in atmosphere, oxygen in oceans, great oxygenation event (changes color of earth)

1. Methane in atmosphere

2. all iron deposited in Banded Iron Formations, oxygen enters atmosphere when most of dissolved iron is in BIF

3. Oxygen builds up in Ocean by stromatolites that can photosynthesize & produce O2

4. Oxygen leaks from ocean to atmosphere resulting in Earth's changed color