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Geography IGCSE > 2.1 Earthquakes and volcanoes > Flashcards

2.1 Earthquakes and volcanoes Flashcards

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1
Q

Crater def?

A

Depression at the top of a volcano following a volcanic eruption. It may contain a lake

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2
Q

Lava def?

A

Molten magma that has reached the Earth’s surface. It may be liquid or may have solidified

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3
Q

Shield volcano def?

A

Gently sloping volcano produced by very hot, runny lava

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4
Q

Cone volcano def?

A

Steeply sloping volcano produced by thick lava

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5
Q

Ash def?

A

Very fine-grained volcanic material

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6
Q

Cinders def

A

Small-sized rocks and coarse volcanic materials.

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7
Q

Magma def?

A

Molten rock within the Earth. When magma reaches the surface it is called lava

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8
Q

Magma chamber def

A

The reservoir of magma located deep inside the volcano

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9
Q

Pyroclastiques flow def

A

Super hot (700*c) flows of ash, pumice and steam at speeds of over 500km per hour.

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10
Q

Pumice def

A

Volcanic rock

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11
Q

Vent def

A

The channel through which volcanic material is ejected

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12
Q

Dormant def? (volcano)

A

Volcanoes which have not erupted for a very long time

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13
Q

Active def? (volcano)

A

A volcano currently showing signs of activity

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14
Q

Extinct def? (volcano)

A

A volcano which has shown no signs of volcanic activity in historic times

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15
Q

Intensity def?

A

The power of an earthquake, this is generally measured using the Richter Scale or sometimes the Mercalli scale

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16
Q

Richter Scale def?

A

An open ended scale to record magnitude of earthquakes - the higher the number on the scale, the greater the strength of the earthquake. There are more small earthquakes than large

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17
Q

Mercalli Scale def?

A

Relates ground movement to commonplace observations of, for example, light bulbs, bookcases and building damage

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18
Q

Epicentre def?

A

The point on Earths surface directly above the focus of an earthquake. The strength of the shock waves generally decrease away from the epicentre.

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19
Q

Focus def?

A

The position within the Earth where an earthquake occurs. Earthquakes may be divided into shallow-focus and deep-focus earthquakes depending on how far below the Earths surface they occur

20
Q

What’s the shape of a volcano dependent on?

A

Type of lava
Very hot, runny lava = shield volcano
Thick material = cone volcano

21
Q

Composite/cone (strato-volcanoes)

are?

A

Steep volcanoes
formed of viscous acidic lava, ash and cinders.
Found at Destructive plate margins
(may have more than one cone)

22
Q

What are shield volcanoes?

A

Low-angle volcanoes
formed of runny basaltic lava
found at constructive plate margins and hotspots.

23
Q

What is an earthquake?

A

A sudden, violent movement of the earth. It occurs after a build up of pressure causes rocks to give away

24
Q

Types of crust

A

Continental

Oceanic

25
Q

Describe Continental crust

A

35-70km thickness
very old, mainly over 1500 million years
Lighter, with an avarage density of 2.6
Usually made up of granite

26
Q

Describe oceanic crust

A

6-10km thickness
younger rock, under 200 million years
Heavier with an avarage density of 3
Mainly basalt

27
Q

Describe the destructive boundary process

A

The oceanic crust moves towards continental.

Due to oceanic being more dense it sinks beneath it, deep sea trenches and island arcs are formed

28
Q

Describe the Constructive boundary process

A

Two plates move apart from each other; new crust is formed, creating mid-ocean ridges, volcanic activity is common

29
Q

Describe the collision process from two continental crusts

A

Two congenital crusts collide, as neither of them sink they are folded up into mountains

30
Q

describe the Conservative boundary process

A

Two plates move sideways past each other but land is neither destroyed nor created

31
Q

What causes most earthquakes

A

Nuclear testing
the weight of large dams
drilling for oil/fracking

32
Q

Where do most earthquake occur?

A

Plate boundaries

33
Q

How does an Earthquake happen

A

Release of pressure as two plates move in different direction or at different speeds

34
Q

Where do volcanoes occur

A

Mainly at plate boundaries however some occur in the middle of a plate, at location known as hotspots

35
Q

What causes eruption

A

Rising magma entering a magma chamber…when pressure in the chamber is great enough eruption occurs

36
Q

Primary hazards of earthquakes

A

Ground shaking

Surface faulting

37
Q

Secondary Hazards of earthquakes

A

Ground failure and soil liquefaction
Landslides and rockfalls
Debris flows and mudflows
Tsunamis

38
Q

impacts of earthquakes

A

Loss of life
loss of livelihood
Total or partial destruction of building structure
interruption of water supplies
Breakage of sewage disposal systems
Loss of public utilities such as electricity

39
Q

Volcanoes direct hazards

A 
Volcanic bombs 
Lava flows
Ass fallout 
Volcanic gas
Lahars (mudflows)
Earthquakes
40
Q

Volcano indirect hazards

A

Atmospheric ash fallout
Landslides
Tsunamis
Acid rainfall

41
Q

Socio-economics impacts of volcanoes

A 
Destruction of settlements
Loss of life
Loss of farmland + forrest’s 
Destruction of infrastructure 
Distrusting of communications 
Reduced tourist arrivals
42
Q

Opportunity’s provided by volcanoes

A

Fertile soil
New land and islands for people to live on
mineral rich soil
important as tourist destinations

43
Q

Case study: Soufrière Hills, Montserrat

A

Thé Soufrière Hills volcanoes erupted in 1995 after being dormant for nearly 400 years. Killed 19 people. Evacuation of capital city Plymouth.
Major redevelopment of housing, schools, hospitals and a new airport.

Montserrat observatory set up to monitor changes…
checks size and shape of volcano
use seidmometers to check for internal changes within crust
measure emissions of sulfur

44
Q

How do you reduce impacts of earthquakes (main ways)

A

Better forecasting and warning
Building location
building design
emergency procedures

45
Q

How can you predict and moniter earthquakes

A

Small-scale ground surface changes
ground tilt
change in rock stress
micro-earthquake activity (cluster of small quakes)
changed in radon gas concentration
unusual animal behaviour, especially toads

46
Q

CASE STUDY: Nepal, 2015 - an earthquake in an LEDC

A

2015 Nepal Earthquake - magnitude 7.8 - 25tg April as a result of the indian plate colliding with the Eurasian plate.

Epicentre of the earthquake was 80km north of Capital, shallow focus of 15km.
Occurred around midday

9k deaths in main earthquake and 200 were killed in an aftershock of 7.3
Fatalities were less in rural parts as less buildings.
Economic cost of 7billion dollars - 35% of Nepals GDP. Asian development bank provided 3 million grant for emergency relief, including shelter, food, blankets and cooking utensils

Geography IGCSE (9 decks)

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