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Geology > Structure and Composition of the Earth and Plate Tectonic Theory > Flashcards

Structure and Composition of the Earth and Plate Tectonic Theory Flashcards

1
Q

What is the layer between the crust and the mantle?

A

The Moho

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2
Q

What is the density of oceanic crust?

A

2.9 g/cm3

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3
Q

How thick is oceanic crust?

A

5-10km

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4
Q

What is the composition of oceanic crust?

A

Basalt

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5
Q

What is oceanic crust rich in?

A

Fe and Mg

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6
Q

What is the density of continental crust?

A

2.7 g/cm3

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7
Q

How thick is continental crust?

A

90km

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8
Q

What is the composition of continental crust?

A

Granite

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9
Q

What is continental crust rich in?

A

Al and Si

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10
Q

What is the density of the mantle?

A

3.3 g/cm3

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11
Q

What is the composition of the mantle?

A

Peridotite

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12
Q

What is the density of the core?

A

12 g/cm3

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13
Q

What is the composition of the core?

A

Iron and nickel

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14
Q

Where is the 1,300 degree isotherm?

A

Between the lithosphere and asthenosphere

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15
Q

What state is the lithosphere?

A

Rigid

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16
Q

What state is the asthenosphere?

A

Rheid

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17
Q

Where is the Gutenberg Discontinuity?

A

Between the mantle and the outer core

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18
Q

Where is the Lehmann Discontinuity?

A

Between the outer and inner core

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19
Q

What state is the outer core?

A

Liquid

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20
Q

What state is the inner core?

A

Solid

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21
Q

Define Lithospheric Plates

A

Regions of the Earth’s crust and upper mantle that are fractured into plates that move across a deeper plasticine mantle

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22
Q

What are the seven major tectonic plates?

A

African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, South American

23
Q

What are the four classifications of rock by Victor Goldschmidt?

A

Lithophile (rock loving), Siderophile (iron loving), Chalcophile (ore loving), Atmophile (gas loving)

24
Q

What is a limitation of Goldschmidt’s Classification?

A

It can depend on temperature, pressure and the chemical environment e.g. pH

25
Q

Define Minerals

A

Naturally occurring inorganic chemical compounds or elements with compositions that can be expressed as chemical formulae

26
Q

What can minerals be identified through?

A

Compositions, Atomic structures, Physical properties

27
Q

Define Silicates

A

Minerals that contain a fundamental building block called a silica tetrahedron

28
Q

What is a silica tetrahedron made from?

A

Four oxygen bounding a single silicon

29
Q

What are the five types of silica tetrahedron?

A

Single (e.g. olivine), Single chain (e.g. augite), Double chain (e.g. hornblende), Sheet (e.g. mica), Framework (e.g. quartz)

30
Q

What eight diagnostic properties of minerals?

A

Colour, Crystal shape, Lustre, Hardness, Cleavage, Relative density, Streak, Reaction with acid

31
Q

What are the four types of lustre?

A

Metallic, Vitreous, Greasy, Pearly

32
Q

What is the hardness of a fingernail on Mohs Hardness Scale?

A

2.5

33
Q

What is the hardness of a copper coin on Mohs Hardness Scale?

A

3.5

34
Q

What is the hardness of a steel pin on Mohs Hardness Scale?

A

5.5

35
Q

What are four pieces of direct evidence for the structure and composition of the earth?

A

Rocks at the surface, Boreholes and mines, Ophiolites, Volcanic rocks with xenoliths

36
Q

What is P wave velocity affected by?

A

Rigidity and incompressibility

37
Q

What is S wave velocity affected by?

A

Density and rigidity

38
Q

Define Shadow Zone

A

Region of the earth that receives no or just some of the different seismic waves

39
Q

What causes P wave shadow zones?

A

Due to the change from solid mantle to liquid outer core causing the P waves to slow down and refract from this surface

40
Q

What causes S wave shadow zones?

A

Due to the change from solid to liquid outer core, the liquid doesn’t allow the S waves to propagate through it

41
Q

What is the average density of the earth?

A

5.5 g/cm3

42
Q

What are the two main types of meteorite found on earth?

A

Iron meteorites and Stony meteorites

43
Q

What do iron meteorites represent?

A

The core

44
Q

What do stony meteorites represent?

A

The crust and the mantle

45
Q

What three things does the earth’s magnetic field change in?

A

Strength, Position of the poles relative to the axis, N and S poles intermittently switch positions

46
Q

Define Geotherm

A

A line that shows temperature variation of rock with depth

47
Q

Define Geothermal Gradient

A

Change in temperature over a given depth

48
Q

When the geotherm is higher than the solidus…

A

The rock partially melts

49
Q

What are four pieces of evidence which confirms the earth is hotter inside than at the surface?

A

Temperature in mines, Hot springs, Volcanic activity, Surface heat flow

50
Q

What are two sources of internal energy/heat?

A

Initial heat from the Big Bang, Break down of radiogenic elements

51
Q

What are six pieces of evidence to define plate boundaries?

A

Earthquake zones, Volcanoes, Trenches and rifts, Mountain belts, Heat flow, Variation in gravity readings and anomalies

52
Q

What are three mechanisms for plate movement?

A

Convection currents, Ridge push, Slab pull

53
Q

When are negative magnetic anomalies induced?

A

When the rock cools and solidifies with the Earth’s north magnetic pole in the southern geographic hemisphere

54
Q

What are four factors affecting gravity?

A

Radius of the earth, Latitude, Altitude, Density of the rocks

Geology (16 decks)

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