Tectonics (year 9)

Question 1

Draw and label a diagram of a volcano

Answer 1

Include:

Crater, Cone, Ash layer, Side Vent

Question 2

What is the definition of an active volcano

Answer 2

If it has erupted recently and is likely to do so again

Question 3

What is the definition of a dormant volcano

Answer 3

If it has not erupted for years, or even centuries, but still seeps has sometimes

Question 4

What is the definition of an extinct volcano?

Answer 4

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

Question 5

How are conservative plate boundaries formed and give an example of one

Answer 5

• 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

Question 6

How are destructive plate boundaries formed and what is an example of one

Answer 6

• 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

Question 7

How are collision plate boundaries formed?

Answer 7

• 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

Question 8

How is a constructive margin formed and what is an example of one?

Answer 8

• 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

Question 9

Where did the Haiti earthquake take place? ⭐️

Answer 9

In Haiti, the Caribbean and North American Plates slide past each other, forming a conservative plate boundary

Question 10

When did the Haiti earthquake take place? ⭐️

Answer 10

12th January 2010

Question 11

Why did the Haiti Earthquake happen? ⭐️

Answer 11

• 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.

Question 12

Explain the primary impacts of the Haiti earthquake ⭐️

Answer 12

• 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.

Question 13

Explain the secondary impacts of the Haiti Earthquake ⭐️

Answer 13

• 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.

Question 14

Describe briefly the global distribution of volcanos

Answer 14

• 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

Question 15

What is the mantle also known as?

Answer 15

The mesosphere

Question 16

What are the different layers of the earth, in order from the centre to the outer layer?

Answer 16

Inner core, outer core, mantle (mesosphere), asthenosphere and the crust

Question 17

What are features of the crust?

Answer 17

• solid rock
• depth of 10-70 km
• very thin compared to other layers
• sits on mantle
• two different types: continental and oceanic crust

Question 18

What are features of the mesosphere?

Answer 18

• 80% of earth’s volume
• upper part is rigid
• made of molten rock (magma)
• currents from this layer move the plates above

Question 19

What are features of the outer core?

Answer 19

• very dense
• surrounds the inner core
• very hot
• molten iron

Question 20

What are features of the inner core?

Answer 20

• solid, dense iron
• over 6000 degrees Celsius
• some heat from here rises and warms the crust

Question 21

How are tsunamis formed?

Answer 21

Tsunamis form when a destructive plate boundary suddenly jolts. The energy released during this is put into the sea, causing a tsunami

Question 22

What are convection currents?

Answer 22

• 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

Question 23

What is a shield volcano?

Answer 23

• it is round and has smooth sides, like a shield
• it is formed through gentle lava eruptions
• it has many solid lava layers

Question 24

What is a composite cone?

Answer 24

• a volcano with many layers
• very tall
• often have side vents and conelets
• have a large crater on top

Question 25

Draw a diagram of a shield volcano

Answer 25

Include:

Vent, lava layers, crust, magma chamber

Question 26

Draw a diagram of a composite cone

Answer 26

Include:

Crater, dyke, ash layers, flank eruption, lava flow, conelet, crater, lava layers, crust

Question 27

What are three examples of eruptions of shield volcanoes?

Answer 27

Kilauea (last eruption May 2018)
Mauna Loa (last eruption April 1984)
Kathala (last eruption 2007)

Question 28

What are three examples of eruptions of Composite Cones

Answer 28

Mayon volcano (last eruption 2018)
Mount Fuji (last eruption December 1707)
Mount Rainier (last eruption 1894)

Question 29

What are the differences between composite cones and shield volcanoes?

Answer 29

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

Question 30

What are the different consequential activities of volcano eruptions?

Answer 30

Pyroclastic flows, ash clouds, Lahars, poisonous gases, lava or volcanic bombs, lava flows

Question 31

What are pyroclastic flows?

Answer 31

• 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

Question 32

What are ash clouds?

Answer 32

• 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

Question 33

What are Lahars?

Answer 33

• 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

Question 34

What are poisonous gases?

Answer 34

• 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

Question 35

What are volcanic/lava bombs?

Answer 35

• 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)

Question 36

What are lava flows?

Answer 36

• flows of lava
• travel at a couple of mph (easy to escape)
• can bury and incinerate land
• easy to run away from

Question 37

Draw a diagram showing how an earthquake happens

Answer 37

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

Question 38

What is the Richter scale?

Answer 38

The Richter scale can be used to measure the magnitude (power) of an earthquake using an instrument called a seismograph

Question 39

What are factors which differ the impacts of an earthquake?

Answer 39

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

Question 40

How can buildings be made earthquake proof?

Answer 40

• 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

Question 41

Why do people live in areas with earthquakes and volcanoes?

Answer 41

• 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