Chapter 2: Geological Oceanography Flashcards
Textbook Chapter
What are the World’s Ocean Basin?
1) Pacific
2) Atlantic
3) Indian
4) Arctic
5) Southern Ocean
How did Earth and Oceans form?
Big Bang 15 bya
Earth originated with solar system
4.5 bya
Density stratification of molten earth was
Density = mass/volume
Core: inner and outer
4000 degrees
Inner
Iron and solid
Outer
Iron, nickel alloy, gold, platinum, and uranium, and molten
Mag field
Due to spinning inner core
Mantle: lower and upper
1) Magnesium + iron
2) Lower solid, upper plastic (semisolid swirls)
Crust
Oxygen, silicone dioxide, magnesium, irons
Two kinds of crusts
Oceanic and continental
Oceanic crust (basalt)
1) Density about 3.0 g/cm^3
2) Only about 5km (3mi) thick
3) Geologically young
4) Dark in color
5) Rich in iron and magnesium
Continental crust (granite)
1) Density about 2.7 g/cm^3
2) 20 to 50 km ( 12 to 30 mi) thick
3) Can be very old
4) Light in color
5) Rich in sodium, potassium, calcium, and aluminum
What shaped Ocean Basin?
1) Geological time scale
2) Continental move
Initial evidence of continental drift
1) Shape of continents when we started exploring and mapping coast
2) Similar geo and fossils on opposite sides
Alfred Wegener (1912)
Theory of Continental Drift, Pangea and Panthalassa
Harry Hess
Seafloor Spreading
What is seafloor spreading?
Magma from mantle rises up at mid-ocean ridges and make new seafloor while pushing crust
Theory of Plate Tectonics
1) Mid-ocean ridges, trenches, and transform faults reveled by sonar
2) Active mid-ocean ridges
3) Sediment layers on seafloor near ridge is thin
4) Rock/sediment further away from ridge older than ones nearer ridge
5) Magnetic anomalies
Lithospheric plates made of
Crust and uppermost part of upper mantle
Plates can have any kind of
Crusts
Plate float on
Plastic upper mantle equals to movement
Plates move apart at ridges and collide at
The trenches
Trench formation
When two plates collide one subducts
Oceanic vs continental
Oceanic subduct
Oceanic vs oceanic
Older oceanic subduct
Continental vs continental (Does not form trench)
Neither subducts or uplift instead
Trenches active geologically in these
1) Volcanoes, earthquake
2) Plates can also slide at shear boundaries (San Andreas Fault)
New theory of plate tectonics
Convection currents and slab pull move plates
How has Earth changed over time?
1) 200 mya: Pangeal/Panthalassa
2) 180 mya: Pangea = Laurasia + Gondvana
What stories can be told by Ocean Sediments?
1) Lithogenous sediment: from breakdown of rocks
2) Biogenous sediment: from skeleton and shells
Ocean sediment can reveal information about
Temperature, atmospheric gases at the time, pH of water and calcereous and siliceous ooze
What are the main current geological features of ocean?
1. Continental Margins
2. Deep Ocean Basin
1) Continental Shelf: 120-200 m depth, submarine canyons, and shelf break
2) Continental Slope: 3000-5000 m depth
3) Continental Rise: Sediment from land
4) Active with passive margins
Deep Ocean Basin
1) Most at 3000-5000 m
2) Abyssal plain
3) Seamounts
4) Trenchs (Marianna = 11,022 m, 36, 070 ft)
Mid-ocean ridge and vents
1) Central rift valley
2) Hydrothermal vents
Hot Spot
Stationary mantle plume vs windshield hypothesis
West Coast of North America Sediment not able to
Accumulate due to steep slope
and sediment is washed away
East Coast of North America sediment is able to
Accumulate because of type of shelf
