Seafloor Flashcards

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1
Q

Geography of the ocean basins

A

Oceans cover 71% of earth in total area
- 61% northern hemisphere
-80% southern hemisphere

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2
Q

Four ocean basins

A

Pacific
Atlantic
Indian
Arctic
(The oceans are interconnected as a single world ocean)

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3
Q

Origin of earth

A

-4.5 billionths ago from dust accumulated form the bing bang
-Early earth was likely molten (hot)
-materials settled by density as they cooled
-Heaviest materials sunk to center of earth

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4
Q

Density

A

Mass per unit volume

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5
Q

Internal estructure of the earth

A

-Core: innermost layer, solid inner core and liquid outer core; iron-rich produces earth’s magnetic field
-Mantle: middle layer, semi-plastic (semi-solid) composition.
-Crust: outermost layer, thinnest portion of the Earth

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6
Q

Oceanic crust

A

Dark-colored mineral material, basalt; denser than continental crust.
Younger mess than 200 millions years old.

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7
Q

Continental crust

A

Light-colored mostly granite; less dense; some 3.8 billions years old

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8
Q

Continental drift

A

-Alfred Wegner (1912)
-Movement of continental masses on the surface of earth.
-All continents had been joined in a single supercontinent, named Pangaea
-Pangaea began breaking up 180 MYA

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9
Q

Plate tectonics

A

Movement of large plate on earth’s crust
- Explains continental drift

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10
Q

Mid-Ocean ridges

A

-Chain of submarine volcanic mountains
- Ridge is displaced by faults in the Earth’s crust called transform faults.
- crust separates creating rifts, sea floor spreads away from the ridges.

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11
Q

Significance of mid-ocean ridges

A

-geological activity is concentrated where plates meet
-earthquakes at ridges and volcanoes at trenches
-sea floor is young at the ridge and gets older as it moves away.

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12
Q

Geomagnetic anomalies

A

-Earth’s magnetic field reverses periodically
-New rock formed from magma records the orientation of earth’s magnetic field at the time the magma colds
-Studies of the sea floor have revealed “stripes” of alternating magnetization parallel to the mid-ocean ridges.

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13
Q

Lithosphere

A

Made up of tectonic plates and top portion of the mantle

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14
Q

Ridges

A

Form edges of plates. Sea floor spreading and new sea floor is being created

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15
Q

Slab pull

A

Causes plates to separate at the ridge

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16
Q

Trenches

A

Depression in the sea floor

17
Q

Subduction

A

Occurs when one plate dips into the mantle under another plate, forms trenches.

18
Q

Island arcs

A

Are chains of volcanic island along trenches

19
Q

Geologic history and continental drift

A

-Pangea surrounded by Panthalassa
- Pangea separated into Laurasia and Gondwana
- Gondwana separated
- Atlantic Ocean grew
- Australia separated, India collied

20
Q

Marine sediments (two types)

A

Lithogenous sediments - derived from the break- down of rocks (weathering)
Biogenous sediments- derived from the skeletons and shells of marine organisms

21
Q

What can we learn from marine sediments?

A

-Earth’s climates has fluctuated rhythmically
- Interglacial periods (warm): sea level rises
-Ice ages (glaciers build up): sea level falls as water is trapped in ice on continents
-Human influence intensifies the greenhouse effect
- sea level projected to rise next century

22
Q

Continental margins

A

Are boundaries between continental crust abs oceanic crust
- continental shelf (most landward)
-continental slope
Continental rise (most seaward)

23
Q

Continental shelf

A
  • Makes up 8% of the ocean’s surface area
  • Richest area of the ocean (number of species)
    -It’s width varies from 1 km to 750 km
  • the shelf ends when the shelf break
24
Q

Continental slope

A

-Edge of a continent
- Begins as the shelf break and extends to the deep sea floor
-Steepest part of the continental margin

25
Q

Continental rise

A
  • formed by a thick layer is sentiment piled on sea floor
    -sediments that have been pushed down from the continental shelf and slope
26
Q

Abyssal plain: Deep ocean basins

A

Most of deep-sea floor (abyssal plain)
-Numerous seamounts - submarine volcanoes
- flat-topped sediments called guyots common
-great biodiversity
-the deepest part of the world
-Mariana trench is deepest in the world 10,994 m (36,070 ft)

27
Q

Hawaiian island formations

A

-Are a chain of seamounts
-form over a hot spot, a plume of magma rising from deep in the mantle
-tectonic plate moves over the stationary hotspot.

28
Q

Hydrothermal vents

A

-Sea water seeps into cracks in the crust and rises in hydrothermal vents.
-Water can be as hot as 350 C (660) F
-Hot water cools quickly, dissolved .sulfide minerals solidify into deposits called black smokers.