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AQA A Level Geography - PHYSICAL > ✅HAZARDS 3.1.5.2 - Plate Tectonics > Flashcards

✅HAZARDS 3.1.5.2 - Plate Tectonics Flashcards

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1
Q

Describe the crust:

A

The thin layer of the outer shell that we live on, 5-10km thick beneath oceans and 70km thick beneath continents, lithosphere

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2
Q

Describe oceanic plates:

A

An occasionally broken layer of basaltic rocks known as sima - silicon and magnesium

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3
Q

Describe continental plates:

A

Bodies of mainly granite rocks, known as sial - silicon and aluminium

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4
Q

What is the lithosphere?

A

The crust and upper mantle, where tectonic plates are formed

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5
Q

How thick is the mantle?

A

2900km

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6
Q

What is the asthenosphere?

A

A layer of soft, plastic like rock that carries the lithosphere

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7
Q

How hot is the core?

A

5000 degrees C

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8
Q

What is gravitational sliding?

A

The movement of tectonic plates under the influence of gravity

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9
Q

What is ridge push?

A

Gravity acting on the weight of the lithosphere near the ridge pushes the older part of the plate in front.

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10
Q

What is slab pull?

A

The lithosphere sinks into the mantle under its own weight following subduction, helping to ‘pull’ the rest of the plate with it.

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11
Q

What events and landforms occur at Constructive boundaries?

A

Volcanoes
Mid ocean ridges
Rift valleys

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12
Q

What events and landforms occur at Destructive boundaries?

A

Powerful earthquakes
Volcanoes
Fold Mountains
Ocean trenches

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13
Q

What events and landforms occur at Collision boundaries?

A

Powerful earthquakes

Fold Mountains

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14
Q

What events and landforms occur at Conservative boundaries?

A

Powerful earthquakes

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15
Q

What is jigsaw fit evidence for tectonic theory?

A

Similarity in outlines of West Africa and South America as well as other continental areas. Best fit at 1000m below sea level.

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16
Q

What is geological fit evidence for tectonic theory?

A

Ancient rock outcrops from South America and West Africa from over 2000 million years ago were continuous

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17
Q

What is Tectonic (orogenic) fit evidence for tectonic theory?

A

Fragments of the Caledonian mountain belt are found in Scotland, England, Greenland, Canada and Scandinavia

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18
Q

What is glacial deposit evidence for tectonic theory?

A

300 million year old deposits found in Africa, Australia, Antarctica, South America and India suggest ancient ice sheet

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19
Q

What is fossil evidence for tectonic theory?

A

Bands of identical fossils lie across continents, particularly of organisms which could not have travelled.

20
Q

What happens at a conservative boundary?

A

Two plates do not directly collide but slide past one another

21
Q

What happens at a constructive boundary?

A

2 plates are moving apart, leaving a gap for magma to rise up through. Volcanoes form but don’t erupt with force and earthquakes occur

22
Q

Where are rift valleys common?

A

Where 3 plates meet at a junction

23
Q

What happens at destructive boundaries?

A

Dense oceanic plate descends beneath less dense continental plate. Oceanic plate melted due to friction forming magma

24
Q

What happens at collision boundaries?

A

Two plates of similar densities move together, causing the material between them to buckle and rise up

25
Q

Where do rift valleys form?

A

On constructive boundaries

26
Q

How do rift valleys form?

A

Magma rises and plates move apart
Over a magma chamber, crack and faults appear
Blocks of crust descend into mantle, creating steep sided valleys
Central plateaus sink in the middle, forming lakes
Mountains often form on the sides

27
Q

What is a Benioff zone?

A

The further the rock descends, the hotter it gets. Together with the heat from friction begins to melt the plate to magma

28
Q

What boundaries do ocean trenches form at?

A

Destructive

29
Q

What are convention currents in the asthenosphere

A

Movement of hotter material in the mantle rising (causes magma to rise)

30
Q

What is Plate Tectonic Theory

A

Idea the Earth’s surface is split into plates which glide over the Mantle (asthenosphere)

31
Q

Destructive Plate boundary Example: what is the Ring of Fire

A

Surrounds Pacific
40,000 km
Many intense active volcanoes+ earthquakes
Krakatoa 1883 eruption, 2010 Japan EQ

32
Q

Destructive Plate boundary Example: what is the Alpide Belt

A

Includes the Indian Plate, Eurasian Plate. Orogenic (mountains formed, e.g Himalayas)
15,000 km

33
Q

Constructive Plate Boundary: Mid Atlantic Ridge

A

The largest mountain chain in the world 16000km, is underwater.
South American and African Plates

34
Q

Slab Pull

A
35
Q

Ridge Push

A

The upwelling of hot material creates a buoyancy effect which creates an ocean ridge. Here the plate experiences the force of gravity, pushing the plates

36
Q

Rift Valley Example

A
37
Q

What boundary do island arcs form at

A

Destructive
Oceanic and oceanic plates

38
Q

How do island arcs form

A

Denser oceanic plate subducts
In the benioff zone, magma upwelling occurs
Volcanic island form

39
Q

What is an example of an island arc

A

Pacific plate subducts under the Philippine plate
Line of volcanic islands including Guam appear

40
Q

What is a plume

A

a hot column of magma which rises from deep within in the Earth

41
Q

Why does not all volcanic activity occur at a plate boundary

A

Due to tectonic plate movement away from a hotspot where a volcanic island can form

42
Q

What is a hotspot

A

A hot spot is an area on Earth over a mantle plume or an area under the crust where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the crust and volcanic activity due to the localised heating between the crust and mantle

43
Q

How do island chains form

A

Theory:
Active volcanoes form from mantle plume above hotspot
Tectonic plate moves taking with it the volcano, hotspot remains stationary
Another volcano is formed over the hotspot
Process continues until a chain is formed
Islands furthest from hotspot are oldest

44
Q

Example of an island chain

A

Hawaiian islands
Youngest island is submarine volcano The Loihi Seamount, which will eventually emerge into a new island in the chain
Has active shield volcanoes like Mauna Loa
6000km long
shows movement of tectonic plates (the plate moves approx. 10 cm a year)

45
Q

What is a sill

A

if magma moves along horizontal bedding planes, it cools to form sills
Often in composite volcanoes
Lava can erupt out of - causing volcano eruptions to be unpredictable - not sure where lava will come from

46
Q

What is a dyke

A

If the magma is intruded along vertical joints, it forms dykes

AQA A Level Geography - PHYSICAL (35 decks)

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