Restless Earth Flashcards

1
Q

Describe continental crust

A

Think but less dense

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2
Q

How many major tectonic plates are there

A

Seven

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3
Q

How do destructive plate margins move

A

Towards each other

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4
Q

In detail what happens when the two plates move towards each other at a destructive margin

A

The lighter continental crust stays above but the oceanic crust goes underneath this is called a subduction zone

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5
Q

What does the rising magma cause at destructive plate boundaries

A

Composite volcanoes

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6
Q

Name the three land features of a destructive plate boundry

A

Fold mountains
Ocean trenches
Composite volcanoes

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7
Q

Why do earthquakes occur at destructive plate boundrys

A

Because energy build up in the subduction zone which forms and earth quake when the palates suddenly jolt under the pressure

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8
Q

How do constructive plate boundrys move

A

Away from each other

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9
Q

What fills up the gap at a constructive plate boundry

A

Magma

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10
Q

Where are constructive margins often found

A

Under the sea

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11
Q

What is formed at a constructive margin

A

Shield volcanoes

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12
Q

Why are islands sometimes formed at constructive margins

A

Because the shield volcanoe produces magma which solidifies above the water

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13
Q

What is the name for the margin in which the plates move across from each other

A

Conservative margins

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14
Q

What occurs at conservative margins

A

Earthquakes

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15
Q

What is the depression in which sediment forms to start the formation of a fold mountain

A

A geosyncline

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16
Q

What happens to the sediment in a geosyncline over time?

A

It turns to rock

17
Q

What happens when pressure for plate movement is put onto the rock inside a geosyncline

A

It is forced upwards

18
Q

What is the name for the tops of a fold mountain

19
Q

What are the dips of a fold mountain called

A

A syncline

20
Q

Name the features of a shield volcano

5

A
Only made of lava
Gentle slopes
Wide base 
Regular eruptions 
Runny lava
21
Q

Name the features of a composite volcanoe (5)

A
Made from ash and lava
Steep slopes
Shorter based
Irregular eruptions
Viscous lava
22
Q

Where do earthquakes happen

A

At all margins

23
Q

What is the focus

A

The underground centre of the earthquake

24
Q

What is the epicentre of an earthquake

A

The point on the surface directly above the focus

25
What are shock waves
Waves of energy that move out in all directions from the focus
26
Describe the Richter scale with four points
Measured magnitude Uses sismographs They are logarithmic Measure 1-10
27
Describe the mecaralli scale in three points
Measured by impact on people Measured by human judgement Measured in Roman numerals
28
Name three physical things that make an earthquake worse
Magnitude Shallow focus Ground eg sand is worse as it shakes more
29
Name four human factors that increase an earthquakes severity
Population density Residential area Self built housing Lack of response
30
What could tsunamis be described as
The secondary effect of a earthquake at sea
31
How do tsunamis happen
One plate is stick under another causing tension An earthquake occurs forcing the plate upwards Sea rises causing water to be displaced and is pushed in a direction perhaps towards land
32
Describe oceanic crust
Thin but dense