1b.2 DM - Destructive Plates and Composite Volcanoes Flashcards

1
Q

What landforms could be found at a destructive plate boundary?

A

Ocean trench
Subduction zones
Composite volcanoes

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2
Q

What’s the difference between continental and oceanic crust?

A

Continental is thicker.
Oceanic is thinner.

Oceanic is denser
Continental is lighter.

Continental is granitic.
Oceanic is basaltic.

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3
Q

What happens when plates converge?

A

Gravity causes the denser oceanic crusts to subduct.

This drags the rest of the tectonic plate down.

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4
Q

What hazards happen at destructive plate boundaries?

A

Volcanoes (composite)
Tsunamis
Earthquakes

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5
Q

Why do tsunamis happen at destructive plate boundaries?

A

Undersea earthquake activity as the continental and oceanic plate scrape past each other

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6
Q

Why do earthquakes happen at destructive plate boundaries?

A

The plates converge
The oceanic subducts
It scrapes past the continental plate, building up tension, which is then released

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7
Q

How do volcanoes occur on destructive plate boundaries?

A

Convection currents - the plates collide.
Denser oceanic crust is pushed downwards into the mantle, and melts.
Melted crust has greater gas content
Magma is viscous / andesitic
Composite / explosive volcanoes forms

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8
Q

What’s the shape of a composite volcano and why?

A

Steep, and tall.
Viscous lava doesn’t run very far before it cools, so you get steep sided volcanoes.
The crater is filled with a plug of cooled rock.
The volcano is made up of layers from lava and ash.

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9
Q

Why do earthquakes happen on conservative plate boundaries?

A
Plates slide past each other
Friction occurs
Build up of pressure
-- the release of that pressure causes the earthquake.
This point is called the focus.
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10
Q

What’s the difference between the focus and epicentre?

A

Focus is underground - where the earthquake begins.

The epicentre is above the ground - where the EQ waves reach the surface.

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11
Q

Why are some earthquakes more hazardous?

A

Higher magnitude (Richter scale)
The focus/epicentre is closer to densely populated area
Shallow focus
Can create secondary hazards - tsunamic landslides etc

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12
Q

What can cause a tsunami?

A
Earthquakes
Landslides
Underwater volcanic eruptions
Large meteor strikes
Upward movement of a tectonic plate / movement of plates
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13
Q

How do earthquakes cause a tsunami?

A

Plate movement causes the EQ
Energy is transferred to the water, causing it to move - the water column is displaced
This creates large waves

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14
Q

How do landslides causes a tsunami?

A

Water is displaced

This creates large waves

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15
Q

What is the focus and epicentre of an EQ

A

Focus - where the EQ starts

Epicentre - where the waves reach the surface

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