Final Flashcards
relative dating
sequence of geologic events in a region
Law of superposition
older layer is on bottom; Works best for sedimentary rocks
Principle of original horizontality
sediments are originally deposited as horizontal beds; Use for tilted/bent layers
What causes rocks to bend?
plate collisions or temperature
Folding happens after…
rocks were deposited
Law of cross cutting
An igneous intrusion/fault is younger than the rock layers that it cuts across
Law of inclusions
The inclusion is older than the rock it is in
Angular unconformities
folding
nonconformity
younger sedimentary rock on top of older igneous rocks
disconformity
missing sedimentary rock layers
How MI basin formed?
Deposited as Sea dried up; Forms circular patterns; oldest rocks on edges of basin
Relative dating
a sequence of geologic events
Absolute
the exact age of a rock
Radiometric dating
divide parent isotope by 2 until reach amount left; count # times you divided by 2
Divergent
moving apart; Mid-ocean ridge; Tensional stress
Example of Divergent boundary
Mid-ocean ridge; East African Rift
Convergent
Moving together; Compressional Stress; Trenches
ocean-ocean convergence
Formes deepest trenches; Volcanoes form on ocean floor off continental coast; Island Archs + earthquakes; Andesite
Ocean-Ocean example
Japan; Caribbean Islands
Ocean-Continental Convergence
Trenches (not as deep); ocean subducts b/c more dense; Composite volcanoes; Pumice + rhyolite
Examples of Ocean-COntinental
Mt. St. Helens; Rings of Fire
Transform
Plates sliding past each other; Shearing stress; Shallow earthquakes
Example of transform
San Andreas Fault
How do plates move?
Convection currents + slab/pull
Convection currents
Hot magma rises and cold magama sinks creating a current
Slab pull
Plates pull themselves down at subductive zones due to gravity
How did Wegner change science of geology?
Continental Drift theory
How do magnetic reversals support plate tectonics?
Zebra stripes on ocean floor had to form together
Formation of Himalayas
Convergence of Australian-Indian plate w/ Eurasian palte
San Andreas Fault
Transform fault between North American and Pacific Plate
Andes mountains
Convergent of nazca and South American plates
Mt. St Helens
Convergent of Juan De Fuca and North American plates
Mid Atlantic Ridge
Divergent of North American and Eurasian plates
Red Sea
Divergent of Arabia and African plates
Mariana Trench
Ocean-Ocean Convergence of Pacific and Phillipine Plates
Iceland
Ocean Divergent of North American and Eurasian Plates
How a spit formed…
Ridges of sand tht extends into mouth of an adjacent bay; Created by longshore currents + beach drift; Depositional
How tombolo formed…
Ridge of sand that conects an island to the mainland; Created by longshore currents; Depositional
How baymouth bar formed…
Sandbar that corsses a bay; Sections off bay from open ocean; Depositional
Sea arch
when sides of headlands are attacks by wave refraction; Erosional
Wave cut platfrom
Created from cutting action of surf against rock of coastal land, gradually over hanging rocks erosed; Erosional
Emergent coast
Developed due to an area experiences uplift or result of drop in sea level
Submergent shorline
created when sea level rises or land adjacent to land subsides underwater
Longshore current
Pushes the sand
Ocean sand
Well rounded, well sorted, and usually mainly quartz
Desert sand
angular
Great Lakes sand
Variety of minerals because glaciers
Problems with groins
current erodes sand from beach on leeward side of groin
Problem with seawalls
seaward side of beach experience significant erosion; Eventually wall falls due to reduced width of beach and increased pounding of water
pacific Coastlines
rocksy, tectonically active, beach sand supply from rivers
Atlantic coastlines
subject to hurricans, has barrier islands
Barrier islands
sand deposits
How Morains formed
depsoited along edge of glacier dueing melting
sediment of morians
till
Esker
Curving ridges of stratified drift; deposited by melt water streams;
Sediment of esker
outwash
Kame formation
depsoited at end of meltwater streams (delta); Mined for gravel
Kame sediment
outwash
Kettle lake formation
made from ice blocks
Kettle lake sediment
till
Outwash plain formation
lake meltwater; Formed next to moraines
Drumlin formation
Hills of sediment deposited by glacier
Drumlin sediment
till
How glaciers formed Great Lakes
- each of Great Lakes started as rivers; 2. glaciers carved v-shaped valleys into u-shaped valleys as climate cooled; 3. As climate warmed; glaviers began to melt and retreat; 4. freshwayer from melting glaciers filled in u-shaped valleys
Oldest GL
Erie