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Geography > Tectonics Eq1 > Flashcards

Tectonics Eq1 Flashcards

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1
Q

What are the 3 belts of tectonic activity

A

Alpide belt, Pacific belt, mid Atlantic ridge

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2
Q

What are the 4 steps to the formation of a tsunami

A
  1. Submarine earthquake or volcano occurs, causes vertical water column displacement
  2. A wave travels in all directions
  3. As the wave moves to shallower water, it slows down and gains height
  4. This can travel great distances across land
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3
Q

Cause of tectonic movement: what is mantle convection

A

Magma heats in centre of earth, rises to surface, moves and cools, sinks to core again, no longer believed to be main cause

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4
Q

Causes of intra plate earthquakes

A

Isn’t known fully, may be pre existing weaknesses in plate which reactivates forming seismic waves

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5
Q

Causes of tectonic movement: what is ridge push?

A

When the magma pushes upwards at a divergent plate boundary, the edge of the plate becomes less dense than the surrounding area, so gravity pulls them apart

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6
Q

Causes of tectonic movement: what is slab pull

A

When a plate cools and becomes more dense, it becomes heavier than the asthenosphere and subducts. The weight of this pulls the rest of the plate down.

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7
Q

How is disease caused by earthquakes

A

Illnesses caused by damage to infrastructure and facilities

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8
Q

What are L waves

A

Seismic love waves - slowest and last to arrive, most damaging

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9
Q

What are p waves

A

Primary seismic waves - fastest and first to arrive, only damaging in highest magnitude earthquakes

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10
Q

What are s waves

A

Secondary seismic waves - slower than p waves, more damaging than p waves

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11
Q

What are the secondary hazards of a volcano

A
  • lava flow
  • pyroclastic flow
  • ash fall
  • gas eruption
  • wildfire
  • lahar
  • jokulhlaup
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12
Q

What are the three plate boundaries and what do they mean

A

Divergent - plates move away from each other
Convergent - plates move towards each other
Conservative - plates move past each other

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13
Q

What evidence of tectonic movement is given by Alfred wegener

A
  • continents fit like puzzle pieces
  • glacial deposits in now deserts
  • freshwater animal fossils found on opposite sides of the ocean
  • plant fossils in Antarctica
  • similar rock layers on different continents
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14
Q

What evidence of tectonic movement is given by Harry hess

A

Palaeomagnetism:
- magma rises through divergent plate boundary
- as it cools down, minerals align with the earth’s magnetic field
- when the magnetic field flips, the cooling minerals align in the opposite direction, stripes can be seen of oppositely aligned rocks
- proves seafloor spreading as new land is being formed, plates can be seen moving apart

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15
Q

What happens at a conservative plate boundary

A

No volcanoes

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16
Q

What happens at a continental and continental convergent plate boundary

A

No volcanoes, fold mountains are formed as the plate is pushed up

17
Q

What happens at a continental and oceanic convergent boundary?

A

Explosive eruptions due to rhyolite lava, ocean trench

18
Q

What happens at a divergent plate boundary?

A

Effusive volcanic eruptions due to basaltic magma, rift valley forms, seafloor spreading occurs

19
Q

What happens at oceanic and oceanic convergent boundaries

A

Explosive volcanic eruptions due to rhyolite lava, ocean trench, island arc created

20
Q

What is a gas eruption

A

Eruption of carbon dioxide and sulphur dioxide which can poison people

21
Q

What is a jokulhlaup

A

Glacial outburst floods caused by volcanic eruptions melting snow and ice from glaciers

22
Q

What is a lahar

A

A mixture of water and volcanic rock fragments which flows quickly down a volcano, when a significant rainfall event coincides with eruption

23
Q

What is a tectonic hazard

A

An event caused by the movement of tectonic plates which has the potential to threaten human life and property

24
Q

What is a volcanic hotspot

A
  1. Mantle plume = stationary column of abnormally hot rock rising in the mantle
  2. Pressure creates magma which rises as a volcano
  3. As the tectonic plates move over the mantle plume, a volcanic island chain forms
25
Q

What is an avalanche

A

Mass movement of snow, rock, ice and soil down a mountainside

26
Q

What is ash fall

A

Ash from an eruption which settles on surrounding areas

27
Q

What is basaltic magma

A

Magma that has a low gas content, a low viscosity and a high temperature

28
Q

What is continental crust

A

Less dense, thicker, older

29
Q

What is crustal fracturing

A

When the crust causes rock to break and fracture under the stress and strain of seismic stresses

30
Q

What is lava flow

A

Lava moving away from a volcano after an eruption

31
Q

What is liquefaction

A

When loosely packed waterlogged sediments lose their strength - earthquake

32
Q

What is oceanic crust

A

Denser, thinner, younger

33
Q

What is pyroclastic flow

A

Dense fast moving flow of volcanic ash, solidified lava pieces

34
Q

What is rhyolite lava

A

Lava that has a high gas content, high viscosity and low temperature

35
Q

What is the benioff zone?

A

Zone of seismicity where friction causes earthquakes along the subducted plate surface

36
Q

What is the seismic activity at each plate boundary

A

Convergent - highest magnitude, frequent
Conservative - high magnitude, frequent
Divergent - high magnitude, frequent

37
Q

What is the structure of the earth?

A
  1. Inner core - solid centre of earth
  2. Outer core - liquid outer layer of the core which creates magnetic field
  3. Mantle - solid layer between core and lithosphere
  4. Asthenosphere - partially melted layer of the earth which allows the plates to move
  5. Lithosphere - crust and upper mantle fused together

Geography (18 decks)

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