Geological Oceanography

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guyot

eroded sea mount on top

Average thickness of continental crust

40 km

How many years ago was the big bang?

13.7 Billion years

How many years ago was the sun and earth formed?

4.5 billion years

where did water come from?

80% from asteroids , some from the earth itself. Was around 4.4 bya

Continental Crust contents

Granite, Al, Si, O

Oceanic crust contents

Basalt, Mg, Fe

Average crust thickness of oceanic crust

10 km

who found the line between the mantle and crust?

Mohorovicic

physical description of the lithosphere

Brittle, solid, moves around (tectonics/plates), floating on a semi liquid

physical description of the athenosphere

semi liquid

physical description of the mesosphere

“more solid”

physical description of the outer core

very dense liquid, about 5500 degrees Celsius

physical description of the inner core

solid as a rock, about 6000 degrees Celsius (almost equal to sun’s surface)

bathymetric

measure of depth

continental margin

continental shelf to end of continental rise

continental shelf

Average width of 60 km, depth of 130 m (photic zone), 1/2 a degree slope

Continental slope

4 degree slope, canyons made sediment collapses, 2-3 km deep

continental rise

Foot of continental slope? sediment accumulates at foot of slope, 1 degree slop slightly higher, plane broken up by canyons

deep-ocean basin

not a lot of sediment, very flat (less than 0.5 degrees), varying volcanic topography, 3-5 km deep (average is 4 km)

sea mounts

mountains > 1 km?, don’t reach surface, may be active volcanoes or extinct

trench

steep, deepest part of the ocean, narrow, collision of ocean crust and continental crust

Sigsbee deep

trench in Gulf of Mexico

mid-ocean ridges

one long mountain range, submarine ridge, 60,000 km, elevated, very hot, builds lithospheric plate

when was the first known illustrations of continental drift

1858- Antonia Snider- Pellegrini

What evidence do we have of continental drift

1. distribution of fossils- see how the continents were connected

2. glacier scour - glaciation

3. geological formations

when did we measure longitude

late 1800s

pangea

super continent, broke 250-300 mya, different rate/different direction. thickness and age of marine sediment shows older sediment closer to continents

how old is the oldest marine sediment

200 mya

how old is oldest continental rock crust thing

3.5 byo

convection cell

seafloor spreading (Hess)

Who named the theory of seafloor spreading

Hess, Vine/Matthews 1963

Magnotometer

bands of reversed magnetism, paleomagnetism

Theory of plate tectonics

transform faults (Wilson 1965, Sykes 1967) Activity on transform faults are active only between mid-ocean ridge centers

Passive margin

side of continents closest to mid-ocean range

Active margin

side of continent closest to convergent plate

Wilson cycle

divergence to convergence. Based on heat in the mantle

what is the simplified process of the making of the sun

interstellar gas-- sun--- ignition

What is the simplified process of the making of the planets

dust ring-- gravity-- protoplanets-- planets

how are elements sorted in molten earth

by weight

what are continents mostly made of

granite

what do collision + pressure+ radiation equal

heat

sediment

varying size, both mineral and organic, that is being or has been moved from origin by wind, water, gravity or ice

clasts and clastic rocks

formed from pre-existing rocks

rock cycle

erosion, deposition, transport

chemical weathering

the composition of minerals in sediment changes as it moves from source. some minerals are more stable than others. sediments composition shows source material. Happens when surface is exposed to water

physical weathering

breaking down to different sizes

composition term

clay mineral

gravel size

2.0mm

sand size

o.o625mm- 2.0mm

silt size

0.004- 0.0625mm

clay size

< 0.004 mm

how is texture changed

reduced sizes, increased roundness, generally increases sorting

what does sediment texture provide info on

what sort of mechanical processes have happened

depositional environments

mountains, glaciers, lakes, lagoons, reef, dunes, deep water planes

high energy

fast-moving, turbulent water maintains smaller grains in suspension so they can’t be deposited. Course deposit= sand, gravel

low energy

slow-moving water does not transport coarse sediments. fine-grained deposit= mud

hydraulic sorting

larger gravel clasts stop moving in response to decreasing flow energy

why do clay particles stick together

because of charges

Hjulstrom diagram

given particle size, fluid velocity (erosion, transport, deposition). grain size: direct, linear relationship size and velocity, some particles do not deposit in moving water. mud has cohesion

sedimentation on continental shelf

different from deep sea (shallow water, source is land), shelf (platform nearly flat (1 degree), bredth)

relic sediment

deposited under different conditions from those present today, covers 60% of continental shelf globally, stratigraphy

0-1,000 yrs record

wind, waves and tides, storms move largest volumes

1,000-1,00,000 yrs record

Pleistocene (glaciation, low SL), rivers extended over shelf, coral reefs stranded (died)

1,000,000- 100,000,000 yrs record

plate tectonics

sedimentation in deep ocean

Source of terrigenous sediment far away, does not transmit energy, biogenous ooze and pelagic red clay settle down

terrigenous

runoff, Eolian (wind born)

biogenous

calcereous, siliceous

hydrogenous

precipitate

cosmogenous

meteroites and stuff

pelagic clay

fine grained mud, clay, silt settles slowly from suspension, brown bc Fe oxidized, quarts, feldspar, clay

bulk emplacement

sediment slumps, large mass of loose sediment on unstable slope is redistributed

turbidity current

gravity driven slurries of water/sediment, push aside clear water, build downslope- scouring more sediment as move, stop settle when slope flattens. graded bedding, fining upward, accumulate sequentially, deep-sea fans

deep sea canyons

move lots of sediment in low SL

carbonate compensation depth (CCD)

depth below which CaCO3 shells dissolve, depends on CaCO3 supply, pH, temp, pressure. below CCD only SiO2 ooze deposits

hydrogenous sediment

precipitates from seawater, phosphorite- organic material, metal sulfides, manganese nodules

deltas

right on edge of coast is where the sediment is mostly deposited; river- dominated, wave-dominated, tide-dominated

what does sphericity depend on?

composition

What are the parts of a beach?

Toe, swash zone, high tide line, berm crest, berm

what does sediment transport depend on

depends on competence of flow (speed/velocity/energy of flow)

bedload

hits bottom, creep (rolling down), saltation (picked and dropped and repeat)

orthogonal

90 degrees from wave crest

how does the shape of the land affect waves

can change the angles

transport

not completely parallel, net transport along shore, water moves along the shore (longshore/littoral current)

sediment transport

swash and backwash

wave setup

amount of water that is carried to shore, and where it hits the land. pressure gradient creates long shore current (not wind related), rip current/tide

Ilmenite

TiSiO

Magnetite

FeSiO

Tourmaline

green sediment

Sediment budgeting

Is there net erosion? Is there net deposition?

Inputs - outputs can =

1. steady state

2. accretion (more in than out)

3. Erosion (more out than in)

What are the three ways that Barrier Islands can form?

1. Submergence of a coastal sand ridge --relic beach ridge

2. Segmentation of a sand spit --longshore drift/current

3. emergence of a longshore bar -- made by a man at GCRL

what is the delta lobe cycle

delta--abandonment--submergence--submergence--reoccupation

what are the habitats of barrier islands (6) due to zonation

1. beach

2. dune

3. grassland

4. shrub thicket

5. maritime forest

6. marsh