Theme 2 - 2.1 - Earthquakes And Volcanoes Flashcards
(95 cards)
1
Q
Define crater.
A
Depression at the top of a volcano following a volcanic eruption. It may contain a lake.
2
Q
Define lava.
A
Molten magma that has reached the Earth’s surface. It may be liquid or may have solidified.
3
Q
Define shield volcano.
A
Gently sloping volcano produced by very hot, runny lava.
4
Q
Define cone volcano.
A
Steeply sloping volcano produced by thick lava.
5
Q
Define ash.
A
Very fine-grained volcanic material.
6
Q
Define cinders.
A
Small-sized rocks and coarse volcanic materials.
7
Q
Define magma.
A
Molten rock within the Earth.
8
Q
What is the difference between magma and lava?
A
Magma is in the Earth, while lava is above the surface.
9
Q
Define magma chamber.
A
The reservoir of magma located deep inside the volcano.
10
Q
Define pyroclastic flow.
A
Super hot (700*C) flows of ash, pumice and steam at speeds of over 500km/h.
11
Q
Define vent.
A
The channel through which volcanic material is ejected.
12
Q
Define dormant.
A
Volcanoes which have not erupted for a very long time but could erupt again.
13
Q
Define active.
A
A volcano currently showing signs of activity.
14
Q
Define extinct.
A
A volcano which has shown no signs of volcanic activity in historic times.
15
Q
Define intensity.
A
The power of an earthquake (generally measured using the Richter or Mercalli scale).
16
Q
Define Richter scale.
A
An open-ended scale to record magnitude of an earthquake.
17
Q
Define Mercalli scale.
A
A scale used to determine the ground movement of an earthquake by using observations of light bulbs, book cases, etc.
18
Q
What is the difference between the Richter scale and Mercalli scale?
A
- Richter -> Energy of an earthquake -> seismograph
* Mercalli -> Effect of an earthquake -> Observation
19
Q
Define epicentre.
A
The point on the Earth’s surface directly above the focus of an earthquake.
20
Q
Define focus.
A
The position within the Earth where an earthquake occurs. This determines whether the earthquake is shallow-focus or deep-focus.
21
Q
What determines whether an earthquake is shallow-focus or deep-focus?
A
The depth of the focus below the surface.
22
Q
What determines the shape of a volcano?
A
The type of lava it contains.
23
Q
What type of volcano does hot, runny lava produce?
A
Gently sloping shield volcanoes.
24
Q
What type of volcano does thick material produce?
A
Steep sided cone volcanoes.
25
What type of scale is the Richter scale?
Logarithmic - an earthquake measuring 7.0 is 10 times as powerful as a 6.0
26
Describe the structure of the Earth from centre to outside.
* Inner core
* Outer core
* Mantle
* Crust
27
What is the lithosphere?
The uppermost mantle and crust.
28
What is the asthenosphere?
The upper part of the mantle, just below the lithosphere. Convection currents happen here.
29
What are the main types of volcano?
* Composite
* Shield
* Supervolcano
30
What is another name for a composite volcano?
Stratovolcano
31
What is a composite volcano and what are its features?
* Formed from viscous acidic lava, ash and cinders
* Steep sides
* Alternating layers of lava and ash
* Periodic explosive eruptions -> Pyroclastic flows
* Found at destructive margins
* May have several secondary cones
32
What is a shield volcano and what are its features?
* Formed of runny basaltic lava
* Gentle sides
* Frequent but gentle eruptions
* Found at constructive margins
33
What gives a composite volcano its shape?
The lava it erupts does not travel very far and there is not usually much of it.
34
What gives a shield volcano its shape?
The lava it erupts travels quite far and is runny.
35
Give an example of a composite volcano.
Mt. Saint Helens - USA
36
Give an example of a shield volcano.
Mauna Loa - Hawaii
37
What is an earthquake?
A sudden, violent movement of the Earth, which occurs after a build-up of pressure causes rocks to give way.
38
What is a plate?
A section of the lithosphere.
39
What is a vent?
A long pipe or tube which allows magma to escape to the surface.
40
What is a magma chamber?
An underground store of magma.
41
What is a crater?
The giant hole left by a volcanic eruption.
42
What are the major tectonic plates?
1) Eurasian
2) North American
3) South American
4) African
5) Indo-Australian
6) Pacific
7) Antarctic
43
Name some minor plates.
* Caribbean
* Juan de Fuca
* Cocos
* Aegean
* Adriatic
* Turkish
44
Learn the location of each plate.
Diagram - Pg 31 of revision guide
45
What are the two types of crust?
* Oceanic
| * Continental
46
What are the features of continental crust?
* Thick
* Very old
* Light
* Light in colour
* Many rock types -> Mainly granite
47
What are the features of oceanic crust?
* Thin
* Young
* Heavy
* Dark in colour
* Few rock types -> Mainly basalt
48
What is the average thickness of continental and oceanic crust?
Continental: 35-70km
Oceanic: 6-10km
49
What is the age of continental and oceanic crust?
Continental: Mainly over 1500 million years
Oceanic: Mainly under 200 million year
50
What is the density of continental and oceanic crust?
Continental: Average density 2.6
Oceanic: Average density 3.0
51
What is the colour of continental and oceanic crust?
Continental: Light
Oceanic: Dark
52
What is the material make-up of continental and oceanic crust?
Continental: Granite (+ silica and oxygen)
Oceanic: Basalt
53
What are convergent plates?
Plates that move towards each other.
54
What are divergent plates?
Plates that move away from each other.
55
What is a transform boundary?
When two plates move along each other.
56
What happens when a continental and an oceanic plate converge?
1. The denser oceanic plate is subducted under the continental plate
2. The continental plate is crumpled and forced up to form fold mountains
3. As the oceanic plate is subducted, friction and heat cause it to melt
4. This make it less dense and causes the magma to rise up through weaknesses in the fold mountains, forming volcanoes
5. A deep ocean trench is formed when the oceanic crust is subducted
6. If this happens at sea, the continental crust is forced up, but forms an island arc instead of fold mountains
7. The build up of pressure can also result in earthquakes
57
What happens when an oceanic and continental plate converge at sea?
It is the same as usual, except when the continental crust is forced up, it forms an island arc instead of fold mountains.
58
Can earthquakes occur where an oceanic and continental plate converge?
Yes, very powerful ones can, due to the build up of pressure during subduction.
59
What happens when two oceanic plates converge?
1. The denser oceanic plate is subducted under the less dense oceanic plate
2. As the oceanic plate is subducted, friction and heat cause it to melt
3. This make it less dense and causes the magma to rise up through the oceanic crust
4. This forms volcanic islands
5. A deep ocean trench is formed when the oceanic crust is subducted
6. The build up of pressure can also result in earthquakes
60
At what boundaries are island arcs made?
Converging oceanic and continental (at sea!)
61
At what boundaries are volcanic islands made?
Converging oceanic and oceanic
62
Give some examples of island arcs.
* Caribbean
* Indonesia
* Japan
* New Zealand
63
Give some examples of volcanic islands.
Aleutian islands
64
Give an example of a convergent continental-oceanic boundary.
South American (Continental) and Nazca (Oceanic)
65
Give an example of a convergent oceanic-oceanic boundary.
South American subducts under the Caribbean
66
What happens when two continental plates converge?
1. Large deformation of rock with no subduction (because plates are of similar density)
2. Rock is 'piled up' and forms fold mountains
3. This pressure can result in earthquakes
4. No volcanes -> Because of no subduction
67
Give an example of a convergent continental-continental boundary.
Indian and Eurasian plate -> Formed the Himalayas
68
What happens when two oceanic plates diverge?
1. Movement of plates allows magma to escape through gap
2. This cools and forms new land - this is called an oceanic ridge (like an underwater mountain range)
3. Eventually, the ridges can break the surface of the water and form new islands
4. Rare and gentle earthquakes
5. Gentle but constant volcanoes
69
Give some examples of islands formed by an oceanic ridge breaking the water surface.
* Iceland
| * Surtsey
70
Give an example of a divergent oceanic-oceanic boundary.
North American and Eurasian -> Mid-Atlantic Ridge + Iceland
71
What happens when a continental plate pulls itself apart (diverging boundary)?
1. Crust pulls in opposite ways, causing land in the middle to collapse
2. This forms a rift valley
3. The Valley fills with lakes and then sea
4. When the ripping is happening, magma can also rise and form volcanoes
72
Give an example of a rift valley.
Great African Rift Valley
73
Give an example of a diverging continental-continental boundary.
The African plate ripping itself apart -> Forming the Great African Rift Valley.
74
Give an example of a volcano formed at a diverging continental-continental boundary.
* Mt. Kilimanjaro
| * Mt. Kenya
75
Wat happens when two continental plates move alongside each other?
1. There can be a huge build up of pressure -> Massive earthquakes
2. No major landforms or volcanoes
76
Give an example of a conservative continental-continental boundary.
North American and Pacific - San Andreas Fault
77
What are the causes of earthquakes?
```
NATURAL
• Release of pressure, usually at plate boundaries
HUMAN ACTIVITY
• Nuclear testing
• Weight of large dams
• Drilling for oil / fracking
```
78
What causes volcanoes?
* Mostly at plate boundaries
| * Some at hotspots
79
What is a supervolcano?
Any volcano capable of producing an eruption with an ejecta volume greater than 1000km3.
80
What is a hotspot?
A hot area with an anomalously hot underlying mantle, often far from any boundaries.
81
What can happen at hotspots?
Over time, magma enters into a magma chamber. When the pressure is great enough, an eruption may occur.
82
What are the primary and secondary hazards of earthquakes?
```
PRIMARY
• Ground shaking
• Surface faulting
SECONDARY
• Ground failure and soil liquefaction
• Landslides and rockfalls
• Debris flows and mudflows
• Tsunamis
```
83
What are the impacts of earthquakes?
* Loss of life
* Loss of livelihood
* Destruction or damage of building structure
* Interruption of water supplies
* Breakage of sewage disposal systems
* Loss of public utilities (e.g. electricity)
* Floods from collapsed dams
* Release of hazardous material
* Fires
* Spread of chronic illness
* Out-migration
* Decreased productivity
* Lack of investment
84
What are the direct and in-direct hazards of volcanoes?
```
DIRECT
• Pyroclastic flows
• Volcanic bombs (projectiles)
• Lava flows
• Ash fallout
• Volcanic gases
• Lahars (mudflows)
• Earthquakes
IN-DIRECT
• Atmospheric ash fallout
• Landslides
• Tsunamis
• Acid rainfall
```
85
What are the (negative) impacts of volcanoes?
* Destruction of settlements
* Loss of life
* Loss of farmland and forests
* Destruction of infrastructure
* Disruption of communications
* Reduced tourist arrivals
* Lack of investment
* Fewer jobs
* Reduced earnings for farmers
* Decreased productivity
* Out-migration
86
What are some opportunities provided by volcanoes?
* New land and islands for people to live on
* Fertile soils
* Soils rich in minerals
* Tourism
87
What can be done to reduce the impact of earthquakes and volcanoes?
* Better forecasting and warning
* Building design
* Building location
* Emergency procedures
88
How can earthquakes by monitored?
* Small-scale ground surface changes
* Ground tilt
* Changes in rock stress
* Micro-earthquake activity (clusters of small quakes)
* Changes in radon gas concentration
* Unusual animal behaviour, especially toads
89
What are lava or volcanic bombs?
Semi-molten pieces of rock thrown out by volcanoes, although they do not travel very far.
90
What are the hazards/problems caused by ash clouds and poisonous gases released by a volcano?
* Ash can cover crops and collapse buildings and cars
* Ash blocks out sunlight for plants
* Ash can disrupt air travel
* Poisonous gases can harm people who breathe them in
91
What are lahars and what hazards do they pose?
* Lahars form when hot ash and gases melt snow and ice, and then mix together.
* The fast moving mudflow can destroy plants and buildings in the way
92
What are the hazards caused by lava flows?
* Can destroy building and property
| * Not much of a hazard to humans, because the flow is very slow
93
What is a pyroclastic flow?
A giant cloud of ash and gas which travels down a volcano at speeds of up to 500km/h, temperatures of over 700*C and can travel over 30km. It will burn, knock over or bury anything in the way.
94
Why do people live in areas at risk of seismic or volcanic activity?
* Opportunities of these things
* May have no money to move
* Other pull factors of the region -> E.g. Employment
95
What causes a tsunami?
1. Volcanic or earthquake activity causes an underwater wave
2. This wave travels to the shore
3. When the waves reach shore, they increase in height, slow down and get closer together
(The initial wave is usually generated at a subduction zone, where there is an elastic rebound of the overriding continental plate -> Ring of Fire)
