2.1 Earthquakes and volcanoes

Question 1

Crater def?

Answer 1

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

Question 2

Lava def?

Answer 2

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

Question 3

Shield volcano def?

Answer 3

Gently sloping volcano produced by very hot, runny lava

Question 4

Cone volcano def?

Answer 4

Steeply sloping volcano produced by thick lava

Question 5

Ash def?

Answer 5

Very fine-grained volcanic material

Question 6

Cinders def

Answer 6

Small-sized rocks and coarse volcanic materials.

Question 7

Magma def?

Answer 7

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

Question 8

Magma chamber def

Answer 8

The reservoir of magma located deep inside the volcano

Question 9

Pyroclastiques flow def

Answer 9

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

Question 10

Pumice def

Answer 10

Volcanic rock

Question 11

Vent def

Answer 11

The channel through which volcanic material is ejected

Question 12

Dormant def? (volcano)

Answer 12

Volcanoes which have not erupted for a very long time

Question 13

Active def? (volcano)

Answer 13

A volcano currently showing signs of activity

Question 14

Extinct def? (volcano)

Answer 14

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

Question 15

Intensity def?

Answer 15

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

Question 16

Richter Scale def?

Answer 16

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

Question 17

Mercalli Scale def?

Answer 17

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

Question 18

Epicentre def?

Answer 18

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

Question 19

Focus def?

Answer 19

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

Question 20

What’s the shape of a volcano dependent on?

Answer 20

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

Question 21

Composite/cone (strato-volcanoes)

are?

Answer 21

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

Question 22

What are shield volcanoes?

Answer 22

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

Question 23

What is an earthquake?

Answer 23

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

Question 24

Types of crust

Answer 24

Continental

Oceanic

Question 25

Describe Continental crust

Answer 25

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

Question 26

Describe oceanic crust

Answer 26

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

Question 27

Describe the destructive boundary process

Answer 27

The oceanic crust moves towards continental.

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

Question 28

Describe the Constructive boundary process

Answer 28

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

Question 29

Describe the collision process from two continental crusts

Answer 29

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

Question 30

describe the Conservative boundary process

Answer 30

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

Question 31

What causes most earthquakes

Answer 31

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

Question 32

Where do most earthquake occur?

Answer 32

Plate boundaries

Question 33

How does an Earthquake happen

Answer 33

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

Question 34

Where do volcanoes occur

Answer 34

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

Question 35

What causes eruption

Answer 35

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

Question 36

Primary hazards of earthquakes

Answer 36

Ground shaking

Surface faulting

Question 37

Secondary Hazards of earthquakes

Answer 37

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

Question 38

impacts of earthquakes

Answer 38

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

Question 39

Volcanoes direct hazards

Answer 39

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

Question 40

Volcano indirect hazards

Answer 40

Atmospheric ash fallout
Landslides
Tsunamis
Acid rainfall

Question 41

Socio-economics impacts of volcanoes

Answer 41

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

Question 42

Opportunity’s provided by volcanoes

Answer 42

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

Question 43

Case study: Soufrière Hills, Montserrat

Answer 43

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

Question 44

How do you reduce impacts of earthquakes (main ways)

Answer 44

Better forecasting and warning
Building location
building design
emergency procedures

Question 45

How can you predict and moniter earthquakes

Answer 45

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

Question 46

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

Answer 46

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