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Oceanography > Origins and structure of ocean basins - 3 > Flashcards

Origins and structure of ocean basins - 3 Flashcards

1
Q

What is isostasy?

A

Mass balance of an object floating upon a fluid medium

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2
Q

What control elevation of an object floating on a liquid medium?

A

Thickness of mass, density of mass and the density of the medium

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3
Q

Why are continents higher than the ocean floor?

A

Continents are thicker and less dense so rise above the supporting mantle rocks more than the sea floor

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4
Q

When was the first ever geological map of the sea floor made?

A

1977

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5
Q

What is echo-sounding?

A

Type of SONAR, time between emission and return of pulse used to measure depth … (multiply half the time from the signals outgoing pulse to its return by the speed of sound in water)

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6
Q

What is the approximate speed of sound in water?

A

1460 m/s

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7
Q

What is multi beam?

A

Echo sounding, fan of sound waves emitted, swathe of depth readings from one pulse

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8
Q

What is altimetry used for?

A

Measuring height and sea surface level and bathymetry

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9
Q

What is the lithosphere?

A

Crust and uppermost mantle

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10
Q

What is the asthenosphere?

A

Partially melted mantle rocks with plastic properties

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11
Q

What is the mesosphere?

A

Deeper, rigid mantle zone

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12
Q

Properties of the earth’s core

A

Molten outer and solid inner, dense, iron-nickle

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13
Q

What are the three distinct physiographic provinces of the ocean?

A
  1. Continental margin
  2. Deep-sea basin
  3. Mid-ocean ridge
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14
Q

What are the sections of a continental margin?

A

Continental shelf, continental slope and continental rise

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15
Q

Below what depth are rocks in the mantle no longer plastic?

A

350km

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16
Q

Define Bathymetry

A

Submarine topography

17
Q

What % of the earths crust projects above sea level?

A

29%

18
Q

What is a Moho?

A

The sharp boundary between crust and upper mantle. It lies deeper below the ground beneath continents than it does beneath ocean.

19
Q

What is an ocean basin?

A

Large portion of ocean floor that lies deeper than 2 km

20
Q

Define tension

A

Pull apart force

21
Q

Define compression

A

Pull together force

22
Q

What is & where do you find normal faults?

A

When crustal rock is displaced vertically, occur along the edges of rift valleys

23
Q

What is a transform fault?

A

Fracture in the crust where movement of rocks is horizontal

24
Q

Where is the strongest magnetic field?

A

At the poles

25
Q

‘Magnetic lines of force are vertically oriented’ meaning …

A

Out at S Pole and in at N Pole

26
Q

What is paleomagnetism

A

When minerals align themselves to the geomagnetic field, recording strength and direction of the geomagnetic field at a given point in time

27
Q

What is a continental margin?

A

Submerged edge of the continents … they can be divided into 3 parts

28
Q

What is the continental shelf?

A

Top of the clastic wedge, slopes seaward at 0.5º from the shoreline to the shelf break, terminates in water between 130-200m deep

29
Q

What is the continental slope?

A

Extends downwards from the shelf, slopes at 4º to a dept of around 2-3km, can be cut with submarine canyons

30
Q

What is the continental rise?

A

Vast sedimentary plain, begins at the bottom of the slope, inclines at 1º and merges with the deep ocean at a depth of 4km

31
Q

What are deep ocean provinces?

A

Located between the continental margin and the mid-oceanic ridge

32
Q

What is an abyssal plain?

A

Flattest area on earth, depths of 3-5km, sediment itself can reach a depth of 1km

33
Q

Who first proposed continental drift?

A

Alfred Wegener

34
Q

What is seismicity?

A

Frequency, Magnitude and Distribution of earthquakes

35
Q

What is a Benioff Zone?

A

An area of increasingly deeper seismic activity

Oceanography (13 decks)

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