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Geography- Hazards > Plate margins and magma plumes > Flashcards

Plate margins and magma plumes Flashcards

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1
Q

How are ‘young’ fold mountains formed?

A

formed due to collisons/subductions

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2
Q

How old are ‘young’ fold mountains

A

generally 30-40 million years old

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3
Q

Give an example of ‘young’ fold mountins?

A

the Himalayas

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4
Q

Give an example of ‘old’ fold mountains?

A

The Cairngorms

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5
Q

Define syncline.

A

dip in mountains

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6
Q

Define anticline.

A

raise in mountains

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7
Q

What can a destructive plate margin also be called?

A

Convergent/ collision

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8
Q

What can a conservative plate margin also be called?

A

Transform

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9
Q

What can a constructive plate margin also be called?

A

Divergent

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10
Q

What happens when continental and continental plates collide?

A

fold mountains form

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11
Q

What happens when Oceanic and continental plates collide?

A

subduction

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12
Q

What happens when oceanic and oceanic plates collide?

A

subduction

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13
Q

What is the Benioff zone?

A

An inclined zone in which many deep earthquakes occur, situated beneath a destructive plate boundary where oceanic crust begins to melt due to friction

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14
Q

What is an ocean trench?

A

A linear depression on the sea floor which runs parallel to the plate boundary and is caused by the subduction of one plate under another

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15
Q

What is an Accretionary wedge?

A

Scraped sediment

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16
Q

What is the plate margin at the Himalayas?

A

Collision plate margin

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17
Q

What plates are at the Himalayas?

A

Indo-Australian and Eurasian (both Continental)

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18
Q

What has formed at the Himalayas?

A

‘young’ fold mountians

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19
Q

How long is the fold mountain chain at the Himalayas?

A

2,400km long

20
Q

What is the plate marigin at the Andes?

A

Destructive plate margin

21
Q

What are the plates at the Andes?

A

Nazca (oceanic) and South American (continental)

22
Q

What has formed at the Andes?

A

Ocean trench

23
Q

How deep is the ocean trench at the Andes?

A

4000m deep

24
Q

What is the plate margin at the Caribbean?

A

Destructive plate margin

25
Q

What are the plates at the Caribbean?

A

Caribbean (oceanic) and North American (oceanic)

26
Q

What has formed at the Caribbean?

A

Puerto Rico trench and the Island Arc chain

27
Q

Give an example of a ridge,

A

Mid-Atlantic ridge

28
Q

Give an example of an ocean trench.

A

Puerto Rico trench/ Mariana trench- Philippines

29
Q

What plates are at the mid-Atlantic ridge?

A

Oceanic and Oceanic

30
Q

How does a ridge form?

A
  • convection currents pull the tow pieces of oceanic crust apart
  • where the crust separates it leaves a thinner bit of lithosphere that rises
  • the weakened crust allows magma to escape
  • the lava builds up in layers to for a ridge
31
Q

What are the characteristics of a ridge?

A

-Longest features on the planet
- transform faults at right angles to the plate boundary

32
Q

What plates create a rift valley?

A

Continental and continental

33
Q

What are the characteristics of a rift valley?

A
  • triggered by plumes of magma
  • normal (parallel) faults
  • volcanoes
  • lakes of valley floors
34
Q

Define magma plumes.

A

Areas of high heat flow within the mantle

35
Q

Give some characteristics of magma plumes.

A
  • random distribution
  • they occur on any plates (middle of plates or plate boundaries)
36
Q

Give an example of a current hotspot.

A

Hawaii

37
Q

How old is Hawaii hotspot?

A

less than 0.7 million years old

38
Q

How long is the Hawaii island?

A

2,600km long

39
Q

How far is Hawaii from the closest plate boundary?

A

3,200 km

40
Q

How does volcanic hotspots form?

A

created as plumes of magma rise through the earths mantle

41
Q

The oldest islands are _______ from the hotspot

A

furthest

42
Q

Why do volcanic earthquakes occur?

A

generated by magma movement

43
Q

Why do tectonic earthquakes occur?

A

because of structural weaknesses at the base of the volcanoes or within the crust below

44
Q

What is basaltic lava?

A
  • runny lava which allows gas to escape easily which leads to effusive eruptions
45
Q

What is the temperature of basaltic lava?

A

over 1000 degrees Celsius

46
Q

What is Andesitic lava?

A

sticky lava which traps gas

47
Q

How does magma plums create a chain of islands?

A
  • convection currents draws heat to a section of the lithosphere
  • The mantle makes its way through the crust
  • Volcanoes form as the magma escapes
  • As the tectonic plates move over the hotspot the volcanoes move further away, reducing their levels of vulcancitity
  • This process starts again with a new volcano forming

Geography- Hazards (19 decks)

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