Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Geology ig, es, pt > Global tectonics: Earth structure > Flashcards

Global tectonics: Earth structure Flashcards

1
Q

Why is the earth an ellipsoid in shape?

A

The centripedal pressure exerted on the North and South poles, as the earth spins on its axis has squashed its shape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the Polar and equatorial radius of the Earth?

A

Polar-6357km

Equatorial-6378km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What depths is the Inner Core between?

A

6371km to approx. 5000km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What metals is the Inner Core believed to be made from?

A

Iron and Nickel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is the Inner Core believed to be solid and what evidence is there to support this?

A

solid due to the extreme pressure

P and S waves move through the core ( S waves generated by P waves), S waves only move through solids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What evidence to do with meteorites is there to suggest the Inner Core is made from Nickel and iron?

A

Meteorite evidence= Believed whole solar system formed same time from a nebula cloud. Nearly all material coalesced to make planets, some remained to make meteorites and asteroids. Meteorites are either iron and nickel or silicate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do we use density to infer the nature of the inner core?

A

There must be a dense material at the centre of the earth because the average density of the earth is 5.5 gm/cm^3 and the average density of the surface rocks is 2.7-2.8 gm/cm^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What depth is the Lehmann Boundary at?

A

5000km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What type of Boundary is Lehmann’s Boundary?

A

It’s a phase boundary between materials of the same composition but in different states (Outer Core and Inner Core)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How big is the Lehmann Boundary?

A

100km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the Lehmann Boundary?

A

A phase boundary. 100km Zone where the rocks change from all liquid through to liquid-solid mix to all solid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What depth is the Outer Core between?

A

5000km to 2900km.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the state of the outer core and how do we know this?

A

Liquid
S waves cannot pass through liquid and they do not pass through he Outer Core. P waves slow down due to the reduction in rigidity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do we know that the Outer Core is made form Iron and Nickel?

A

The density graphs show the same pattern as that of the inner core and the same meteorite evidence is true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the origin of the Earth’s magnetics field?

A

The temperature difference between the outer and inner core set up convection currents in the liquid outer core. The convecting mass of molten iron generates electricity which induces magnetism.- self exciting dynamo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What depth is the Gutenburg Boundary at?

A

2900km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is the Gutenburg boundary very clear and distinct?

A

It is at a change of material from metallic to a stony type of material and it also changes state as it goes form liquid to solid.

18
Q

What happens to the P-wave velocity and S waves at the Gutenburg boundary?

A

P wave velocity decreases

S waves stop

19
Q

What depth is the Lower Mantle between?

A

2900km to 700km

20
Q

How do we know the lower mantle is solid?

A

S waves travel through it.

21
Q

Why does the velocity of P waves increase as they pass through the lower mantle?

A

The increasing pressure causes the rocks to become more rigid- less compressible.

22
Q

What is the lower mantle made of?

A

The same type of silicates material as the stony meteorites.

23
Q

How does perovskite form in the lower mantle?

A

The pressure is high, therefore the elements push together to form tight bonds, creating dense silicate minerals- perovskite.

24
Q

What depth is the Upper Mantle between?

A

700km to an average of 30km

25
Q

What is the main rock type of the upper mantle?

A

peridotite

26
Q

What mineral is common in the upper mantle?

A

Olivine is common, but changes to spinel when the pressure increases with depth.

27
Q

What evidence is there to show what the upper mantle is made up of?

A

Rarely lumps of rock are brought up by volcanic action. The main source is kimberlite pipes which go down as far as 250km into the upper mantle.

28
Q

What is the asthenosphere?

A

A layer within the upper mantle where there is 5% partial melting as a result of the intersection of the geothermal gradient and the melting curve of peridotite

29
Q

What is the state of the asthenosphere and what is it composed of?

A

Rheid

peridotite

30
Q

What is the depth of the lithosphere?

A

100km

31
Q

Why is the MOHO different from other discontinuities?

A

It’s not straight and its shape mirrors the surface of the earth

32
Q

What is the depth of the MOHO?

A

Varies from 5-7km under the oceans to 15-90km under the continents

33
Q

How and why can we detect the MOHO?

A

We can detect it because both P and S waves can be reflected by it. This is because there is a difference in the density of the rock above and below

34
Q

What is the thickness of the continental and oceanic crust?

A

Continental- up to 90km thick

Oceanic crust- 5-10 km thick av 7km

35
Q

What is the chemical composition of the continental and oceanic crust?

A

Continental- rich in silica and aluminium SIAL

Oceanic- iron and magnesium

36
Q

What types of rock make up the continental and oceanic crust?

A

Continental- granitic on average but a great variety of sedimentary, metamorphic and igneous
Oceanic- Basalt on average and nearly all igneous

37
Q

What is the density of the continental and oceanic crust?

A

Continental- 2.7 gm/cm^3

Oceanic- 2.9 gm/cm^3

38
Q

What is the age of Continental and Oceanic crust?

A

Continental- between 400 million years- includes the worlds oldest rocks
Oceanic- fairly new maximum of 200 million years to 0

39
Q

What is the structure of the continental and oceanic crust?

A

Continental- deformed

Oceanic- In layers

40
Q

What do we mean by remnant magnetism?

A

Recorded in rocks due to the alignment of their magnetic minerals according to the earth’s magnetic field at the time of their formation.

Geology ig, es, pt (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions