1
Q
Draw and label a diagram of a volcano
A
Include:
Crater, Cone, Ash layer, Side Vent
2
Q
What is the definition of an active volcano
A
If it has erupted recently and is likely to do so again
3
Q
What is the definition of a dormant volcano
A
If it has not erupted for years, or even centuries, but still seeps has sometimes
4
Q
What is the definition of an extinct volcano?
A
If it has not erupted for thousands of years and is not expected to erupt again. Its shape has been worn away by the wind and rain
5
Q
How are conservative plate boundaries formed and give an example of one
A
- when two plates move past each other
- this can build up pressure and friction which can be overcome by a huge jolt forwards
- the seismic waves released by this cause an earthquake
- no major landforms are formed by this as the crust is not being formed nor destroyed and they just slide past each other (no volcanic activity)
- e.g the San Andreas fault in California, where the Pacific and North American plates are moving against each other
6
Q
How are destructive plate boundaries formed and what is an example of one
A
- an oceanic (nazca) plate and a continental plate move towards each other
- a build up of pressure causes the oceanic plate to slide under the continental plate, causing magma to be pushed up to the surface from the mantle. the magma erupts on the surface
- the oceanic plate is pushed under because it is more dense, and will therefore sink whilst it melts under the heat+ pressure
- earthquakes are produced during this by the subducting plate (the nazca plate) because energy is released during the jolt as seismic waves
- an oceanic trench forms because the nazca plate is under the continental plate, creating a dip
- e.g the nazca plate is forced under the South American plate
7
Q
How are collision plate boundaries formed?
A
- two continental plates move towards each other because of convection currents
- when the pressure has built up very much, the plates jolt towards each other, releasing energy as seismic waves, resulting in an earthquake
- when the plates collide, they buckle and bend upwards as they have the same density, forming a mountain range
8
Q
How is a constructive margin formed and what is an example of one?
A
- Two plates move apart due to convection currents
- this creates a gap in the earth’s crust where magma can rise from the mantle and solidify on the surface
- this creates a shield volcano, which has gentle, sloping sides
- these volcanoes have gentle eruptions
- e.g the North American and Eurasian plates
9
Q
Where did the Haiti earthquake take place? ⭐️
A
In Haiti, the Caribbean and North American Plates slide past each other, forming a conservative plate boundary
10
Q
When did the Haiti earthquake take place? ⭐️
A
12th January 2010
11
Q
Why did the Haiti Earthquake happen? ⭐️
A
- There was a slippage along the conservative plate boundary that runs through Haiti.
- many years of built up pressure was released in a sudden jolt and seismic waves of magnitude 7 were the result.
12
Q
Explain the primary impacts of the Haiti earthquake ⭐️
A
- the initial earthquake caused 380,000 buildings to collapse, 30,000 of which were commercial buildings. This endangered people on streets and killed people inside. Haiti is a very poor country so buildings were not well built or earthquake proof. 316,000 people were killed
- there was severe damage to pipes, leading to the outbreak of cholera which killed 7,000 people and affected 530,000. Fresh water was limited.
13
Q
Explain the secondary impacts of the Haiti Earthquake ⭐️
A
- the initial earthquake was followed by two aftershocks of magnitudes 5.5 and 5.9
- the main road in Haiti was blocked for 10 days, slowing down emergency services
- the earthquake left 1.5 million people homeless. These survivors had to be supplied with food, clothes and water as many of the had all of their possessions destroyed
- the airport and port had also been damaged, so it was hard for neighbouring countries such as the Dominican Republic to help.
14
Q
Describe briefly the global distribution of volcanos
A
- Volcanoes are found in belts along plate boundaries
- They are formed by moving continental plates
- only occur at constructive and destructive plate margins.
- e.g the San Andreas fault in California (Pacific and North American plates slide against each other), the Mid Atlantic Ridge (North American and Eurasian Plates in a Constructive plate boundary), the Nazca Plate is pushed under the South American plate in a Destructive plate boundary
- some volcanoes are not found on plate boundaries, these are called hotspots
15
Q
What is the mantle also known as?
A
The mesosphere
16
Q
What are the different layers of the earth, in order from the centre to the outer layer?
A
Inner core, outer core, mantle (mesosphere), asthenosphere and the crust
17
Q
What are features of the crust?
A
- solid rock
- depth of 10-70 km
- very thin compared to other layers
- sits on mantle
- two different types: continental and oceanic crust
18
Q
What are features of the mesosphere?
A
- 80% of earth’s volume
- upper part is rigid
- made of molten rock (magma)
- currents from this layer move the plates above
19
Q
What are features of the outer core?
A
- very dense
- surrounds the inner core
- very hot
- molten iron
20
Q
What are features of the inner core?
A
- solid, dense iron
- over 6000 degrees Celsius
- some heat from here rises and warms the crust
21
Q
How are tsunamis formed?
A
Tsunamis form when a destructive plate boundary suddenly jolts. The energy released during this is put into the sea, causing a tsunami
22
Q
What are convection currents?
A
- Convection currents happen due to the core
- the core is very hot and causes rock in the mantle to rise slowly towards the crust, where it is trapped and is pushed sideways, then it will cool and finally sink back through the mantle
- this causes plates to move either together or apart
23
Q
What is a shield volcano?
A
- it is round and has smooth sides, like a shield
- it is formed through gentle lava eruptions
- it has many solid lava layers
24
Q
What is a composite cone?
A
- a volcano with many layers
- very tall
- often have side vents and conelets
- have a large crater on top
25
Draw a diagram of a shield volcano
Include:
| Vent, lava layers, crust, magma chamber
26
Draw a diagram of a composite cone
Include:
| Crater, dyke, ash layers, flank eruption, lava flow, conelet, crater, lava layers, crust
27
What are three examples of eruptions of shield volcanoes?
Kilauea (last eruption May 2018)
Mauna Loa (last eruption April 1984)
Kathala (last eruption 2007)
28
What are three examples of eruptions of Composite Cones
```
Mayon volcano (last eruption 2018)
Mount Fuji (last eruption December 1707)
Mount Rainier (last eruption 1894)
```
29
What are the differences between composite cones and shield volcanoes?
Shield Volcanoes:
- found in many places, often near the coast
- produced at divergent plate boundaries
- formed by slowly flowing lava which gradually builds up
- typical shield volcanoes measure 3-4 miles in diameter and 1,500-2,000 ft in height
- is shaped like a shield: round, dome shaped and large
Composite Cones:
- found at destructive plate margins
- produced at convergent plate boundaries
- composed of layers of lava, ash and rock debris
- grow through eruptions
- highest in the world is 6.9 km high
- very tall, with many layers and dips
30
What are the different consequential activities of volcano eruptions?
Pyroclastic flows, ash clouds, Lahars, poisonous gases, lava or volcanic bombs, lava flows
31
What are pyroclastic flows?
- giant clouds of ash and gas which will bury anything in its’ way
- travel up to 500km per hour, making them hard to escape and impossible to run from
- can be over 700 degrees Celsius - this would kill anyone instantly
32
What are ash clouds?
- ash released by a volcano in massive clouds
- the weight of falling ash can collapse buildings
- blocks sunlight; blinding humans
- the ash can destroy crops, which is a long term problem, and can lead to starvation
33
What are Lahars?
- fast mudflows
- are impossible to run from as they are very fast
- they drown and bury anything in their’ path
- they happen on snowy mountains, therefore they can be prepared for
34
What are poisonous gases?
- Toxic gases released by volcanoes
- spread very quickly, so are hard to escape
- bad for environment, so are long lasting
- deadly but could be prepared for
35
What are volcanic/lava bombs?
- small balls of lava which spring out of volcanoes
- not serious as they would only do small damage to buildings
- can be prepared for by distancing
- could start fires (very serious)
36
What are lava flows?
- flows of lava
- travel at a couple of mph (easy to escape)
- can bury and incinerate land
- easy to run away from
37
Draw a diagram showing how an earthquake happens
Include:
The focus- the point within the earth where the seismic waves start
The epicentre- the point above the focus on the surface
Seismic waves-waves of energy in an earthquake
The fault
38
What is the Richter scale?
The Richter scale can be used to measure the magnitude (power) of an earthquake using an instrument called a seismograph
39
What are factors which differ the impacts of an earthquake?
Depth of focus- shallower focus means that shaking is more intense, so building are more likely to collapse
Length of earthquake- longer tremors means more damage
Secondary hazards-if earthquakes happen underwater, a tsunami could occur which has devastating effects. Landslides could also happen which are very dangerous
Time of day- at night time, people are more vulnerable as they are unaware of the earthquake
Type of Housing- flats and tower blocks have greater population, so more are injured/killed if they collapse.
Search+rescue- these are better trained in MEDCs than in LEDs
Wealth- MEDCs have more money to repair damages, so it has a lower impact
Magnitude- higher magnitudes mean higher impact because more shaking will cause more buildings to collapse
Location of epicentre- if the epicentre is near a city with a high population, damage will be greater than somewhere more isolated
Building structure- poorer building structures (in LEDCs) mean the buildings are more likely to collapse, causing more deaths
40
How can buildings be made earthquake proof?
- sheer walls with steel bars inside to reduce rocking movement
- automated window shutters to prevent falling glass
- open areas where people can assemble if evacuated
- foundations sunk into bedrock, not clay because clay is very soft
- roads to provide quick emergency access for emergency services
- steel frames which can sway during earth movements and reinforce walls
- computer controlled weights on roof to reduce movement during earthquake
41
Why do people live in areas with earthquakes and volcanoes?
- some people are desperate or don’t have the financial resources to move
- volcanic rock and ash provide fertile land
- tourists are attracted to volcanoes, which increases money for the local economy
- geothermal energy can be harnessed, which is very cheap for locals
- minerals such as diamonds are contained in the lava, these can be mined to make money
- many people stay due to religion e.g in Hawaii people believe the land doesn’t belong to them, it belongs to the gods
- some people don’t want to leave hazardous zones because their family live there
- hazardous zones offer good employment opportunities
Year 9 Geography
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