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Physical Geography - Structures > Earth - Interior > Flashcards

Earth - Interior Flashcards

1
Q

How does wave differ in materisl it is in?

A

Light waves travel fastest thoruhg vaccums, slower in air and slower in water, whilst sound waves do not travel in vaccums, travelling faster in water than it does in air.

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2
Q

Why are the properties of sound waves different to light?

A

Sound waves are variations in pressure, the more force taken to compress a material, the faster they travel.

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3
Q

What are the two types of wave?

A

Compressional
Shear

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4
Q

Comrpessional Waves

A

Waves where particle motion is same direction in which wave is propagating.

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5
Q

Shear Waves

A

These are waves changing the medium of which it travels, altering shape but not volume nor density.

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6
Q

Complication of measuring earth interior with waves…

A

Waves passing through more than one type of material exhibit seperate travel times and wave paths.

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7
Q

Seismic Wave Propogation

A

The passage of waves of compression/shear through rock and soil mediums.

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8
Q

How fast do seismic waves travel through Felsic, Mafic and Ultramafic rocks?

A

6, 7 and 8 km/s respectively.

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9
Q

Composotion of the contiental crust.

A

Low dense granite

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10
Q

Compositon of Ocean

A

Gabbro and Basalt

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11
Q

Mohorovivic Discontinuity

A

Boundary between the crust and the mantle

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12
Q

Composition of the Moho discontinuity…

A

Dense peridotite due to increased velocity of P waves.

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13
Q

Size of ocean, continent and orogenic mountain zone crusts…

A

7km, 33km and 70km.

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14
Q

Composition of upper mantle…

A

Ultramafic peridotite present, greater pressure and temperatures induce greater atomic compression.

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15
Q

Size of the lithosphere…

A

100km but varies geographically, maximising under continents and minimal near spreading centres where new crust forms.

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16
Q

Why does S-wave velocity decrease at base of lithosphere?

A

1% melting of peridotite minerals. (top of Astheno)

17
Q

Asthenosphere

A

The weak ductile layer the lithosphere plates slide.

18
Q

Why does s-wave velocity suddenly increase 400km below the crust?

A

Olvine mineral phase change

19
Q

Where is the second material phase change of olvine?

A

660km

20
Q

Transisiton Zone

A

410-660km where phase changes occur.

21
Q

Seismic Shadow Zone

A

This is an area of the Earth surface when direct P and/or S waves are detected.

22
Q

Rapid s-wave change at core-mantle boundary…

A

2890km where change from solid silicate rock to liquid iron alloy.

23
Q

Why does the core and mantle not mix?

A

Vast density differnece(greater than atmosphere-lithosphere difference)

24
Q

What is the core made of?

A

Iron and nickel and lighter elements

25
Q

What causes internal heat generation?

A

50% of heat is generated by radioactive decay.

26
Q

What drives heat flow and Earth cooling?

A

Conduction and Convection, both lithospheric and interior processes respectively.

27
Q

What is conduction a function of?

A

Atomic vibration and mechanical transfer of heat to surroundings, from hot regions to cool

28
Q

Passive Margins

A

Sites where continents have rifted apart becoming seperated by an ocean.

29
Q

What does conductive cooling cause?

A

Subduction of passive continental margins and thermal subsidence basins

30
Q

Convection of mantle/core…

A

Cyclic nature of heating/rising of a fluid, where its original position is displaced by colder temperatures.

31
Q

Why is convection quicker than conduction?

A

Heat is transported WITH the material.

32
Q

Dynamo Theory

A

This is the mechanism by which a celestial body generates in magnetic field.

33
Q

Nondipole Field

A

The part of the magnetic field contributed by internal geomagnetic processes.

Physical Geography - Structures (10 decks)

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