Unit 2 - Tectonics

Question 1

What are the names for the 4 layers in the Earth?

Answer 1

1. Crust
2. Mantle
3. Outer core
4. Inner core

Question 2

State the following for the inner core:

1. temperature
2. thickness/radius
3. What it mainly consists of

Answer 2

1. around 5,200° C
2. radius around 3,485km
3. a hot dense ball of (mostly) iron

Question 3

State the following for the outer core:

1. temperature
2. thickness
3. What it mainly consists of

Answer 3

1. 4,500° - 5,500° C
2. thickness of about 2,200km
3. mostly liquid iron and nickel

Question 4

State the following for the mantle:

1. temperature
2. thickness
3. What it mainly consists of

Answer 4

1. 500-900°C
2. thickness of about 2,886km
3. it is a silicate rocky shell

Question 5

State the following for the crust:

1. temperature
2. thickness
3. What it mainly consists of

Answer 5

1. 200-400° C
2. average thickness of 0-60km
3. solid rock

Question 6

Explain how a convergent plate boundary forms fold mountains.

Answer 6

1. Plates move together and collide
2. Very violent volcanoes (e.g. Mt St Helens, USA) and Mt. Etna (Sicily) and earthquakes occur.
3. Subduction zones form due to downward movement of the dense oceanic crust into the mantle, beneath the less dense continental crust.
4. Fold mountains (e.g. the Alps and the Himalayas) can form when both plates are pushed upwards by the force of the collision.

Question 7

What type of plate boundary is Mt Laki (Iceland) on?

Answer 7

Divergent plate boundary (accept constructive)

Question 8

Explain how a divergent plate boundary forms ocean ridges e.g. the Mid-Atlantic Ridge.

Answer 8

1. Plates move apart.
2. Less violent volcanoes and earthquakes occur.
3. New sea floor is created at the mid-ocean ridges (e.g. the Mid-Atlantic Ridge) as magma rises up through the ridge and solidifies.

Question 9

Give a location affected by a conservative boundary.

Answer 9

Many locations accepted, examples are:

• San Andreas Fault
• Alphine Fault (N, Zealand)
• North Anatolian Fault (Turkey)

Question 10

Explain how earthquakes can occur with a conservative plate boundary.

Answer 10

1. Plates slide past each other.
2. No crust is destroyed or created, therefore no volcanoes are formed.
3. Plates can ‘stick’; this increases pressure which can be released as violent earthquakes.

Question 11

What is the difference between a collision and convergent plate boundary?

Challenge: Give a location affected by a collision boundary if you can.

Answer 11

A collision boundary has nearly of the same characteristics as a convergent boundary but instead of an oceanic and continental plate being involved, it’s a continental and continental plate e.g. Indo-Australian Plate and Eurasian Plate.

Challenge: A mountain range affected by a collision boundary is the Himalayas.

Question 12

GIve one general characteristics about a volcano.

Answer 12

• A volcano is formed by eruptions of lava and
  ash, with the lava later harding to become new
  rock

OR
- Volcanoes usually are cone-shaped and are
mountains or hills that have become active.

OR
- Volcanic eruptions can happen at convergent
and divergent boundaries but not conservative
boundaries

OR
- Some volcanoes happen underwater - like the
Mid-Atlantic Ridge

Question 13

Explain how a volcano is formed.

Answer 13

1. Magma rises through cracks or weaknesses in
   the Earth’s crust.

2.Pressure builds up inside the Earth.

3.When this pressure is released, eg as a result of
plate movement, magma explodes to the
surface causing a volcanic eruption.

4.The lava from the eruption cools to form new
crust.

5.Over time, after several eruptions, the rock
builds up and a volcano forms.

Question 14

Give 4 features located inside a volcano.

Answer 14

• The magma chamber is a collection of magma
inside the Earth, below the volcano.
• The main vent is the main outlet for the magma
to escape.
• Secondary vents are smaller outlets where the
magma escapes.
•The crater is created after an eruption blows off
the top of the volcano

Question 15

Briefly outline how an eruption occurs,

Answer 15

An eruption occurs when pressure in the magma chamber forces magma up the main vent, towards the crater at the top of the volcano. Some magma will also be forced out of the secondary vent at the side of a volcano.

Question 16

Name a type of volcano found at convergent plate boundaries.

Answer 16

Composite

Question 17

What is a pycroclastic flow?

Answer 17

A mixture of hot steam and debris (the more dense material)

Extra info:
Pyroclastic flows roll down the sides of a volcano at very high speeds and with temperatures of over 400°C.

Question 18

What type of flow causes the largest deaths?

Answer 18

Pyroclastic flows as once people are caught up in one, with all the ash and debris, they have a very little chance of survival

Question 19

Name 4 methods of predicting and preventing volcanic eruptions.

Answer 19

• Using GPS technology to check the bulging of the volcano as magma approaches the surface
• Gas sampling - as changes in the gas composition indicate the activity levels in the magma underground
• Geothermal monitoring from space, to record changes in heat as magma approaches to the surface
• Seismic monitoring, ‘to listen’ to the rising blobs of magma as they force their way upwards and cause small earthquakes

Extra info:
• Looking out the historical records of past eruptions, to tell you if there is a pattern and when the next eruption could occur

Question 20

Name 4 methods of protection against volcanic eruptions.

Answer 20

• Spraying the lava with water so it will harden and become rock, so it will stop flowing
• Putting concrete or rock barriers in the path of the lava, diverting the flow away from villages
• setting off explosives to divert the lava flow
• Digging ditches to divert the flow away from areas at risk

Question 21

State some possible causes for the Monsterrat (Chances Peak) volcanic eruption in 1997.

Answer 21

1. N. American (oceanic) plate is subducted below the continental plate (Caribbean), creating a trench (convergent plate boundary)
2. Oceanic crust melts due to the mantle’s high temperature
3. Build of pressure movement causes earthquakes
4. Molten rock is forced up through fissures in the continental crust, and explodes violently in volcanic eruptions

(Note: for cause 1, the specific plates must be named.)

Question 22

States the effects of the eruption [at Chances Peak (1997)]

Answer 22

1. 5 million cubic metres of ash and rock deposited
2. Trants village covered in 4 square kilometres of ash
3. 19 killed
4. 100-150 homes destroyed
5. Bramble airport destroyed, disrupting air traffic
6. people’s feet and car tyres burnt by ash

Question 23

State the responses made after the eruption.

Answer 23

1. The Montserrat Volcano Observatory was set up to monitor seismic activity
2. Face masks were issued to children to prevent silicosis.
3. 7000 people were evacuated from the island and the immediate danger zones to parts of the UK and other countries
4. The airport began to be rebuilt

Question 24

What type of country is Monsterrat?

Answer 24

LIC (Low income country)

Question 25

What type of country was Mt St Helens in?

Answer 25

US - HIC (High income country)

Question 26

State the possible causes of the 1980 eruption at Mt St Helens.

Answer 26

1. Divergent plate boundary | 2. on the Pacific Ring of fire

Question 27

State the effects of the eruption.

Answer 27

1. 57 dead 2. lateral (sideways) eruption 3. up to 1m of ash settled in the surroundings 4. millions of trees were destroyed

Question 28

State the responses of the eruption.

Answer 28

•monitoring - bulge - tilt meter with lasers ◦fissures going up •exclusion zone set up •evacuation saved 2500 lives (approx.)

Question 29

Explain the meaning of each of these terms: - the focus - the epicentre - seismic waves

Answer 29

focus: the point under the ground where the plates shift and earthquake tremors start epicentre: the point directly above ground and above the focus seismic waves: the tremors given off the plate movement. They are like ripples in a pond, giving off energy outwards

Question 30

Name some characteristics of a primary seismic wave.

Answer 30

- The primary waves are the first one given off. - - They are the faster ones - They can be crucial as a warning sign to the monitoring groups of where the secondary waves will hit first - causing warning systems to start and people getting to higher ground. - They are usually within 5 or 6 seconds between each wave and they travel very fast.

Question 31

Name some characteristics of a secondary seismic wave.

Answer 31

- The secondary waves are the second and the most destructive. - They travel at half of the speed of the primary waves and because of their slow speed - they travel over cities or towns more slowly, leading to tremors that may make buildings collapse and groundwater to surface.

Question 32

Name 2 methods of recording/measuring seismic activity.

Answer 32

Recording: - on a on a seismometer using the Richter scale ◦often referred as 1-10 but is actually unlimited Measuring aftermath: - Mecalli scale ◦a subjective scale that measures the impact of the earthquake ◦from one to twelve (in roman numerals)

Question 33

Name 4 ways of predicting earthquakes

Answer 33

•noting strange animal behaviour as this is often reported before earthquakes •monitoring electrical discharges, because there is some evidence that these rise before an earthquake •recording minor tremors, because some major earthquakes are preceded by small foreshocks •seismic gap theory - USGS (United States Geological Survey)

Question 34

Name 4 ways of protection against earthquakes.

Answer 34

•Providing education to local residents - so they can learn how to prepare and react •Designing buildings that can withstand earthquakes - e.g. flexible steel frames and shutters for windows that might shatter •Planning regulations •Nov. 2008 - L.A. had the largest earthquake drill in history - cost $2 billion •Transamerica Pyramid in Sans Francisco - withstood major earthquakes (swayed 30cm)

Question 35

Name the magnitude on the Richter scale of the Bam earthquake (2003).

Answer 35

6.6

Question 36

Name some possible causes of the earthquake.

Answer 36

-a result of stresses generated by the Arabian plate moving northward against the Eurasian plate at approximately 3 centimetres (1 in) per year -

Question 37

State the effects of the earthquake.

Answer 37

- 300,000 dead - 20,000+ injured - 75,000+ homeless - 85% of buildings destroyed/severely damaged

Question 38

State the responses to the earthquake

Answer 38

-Short term ◦1,600 aid workers from 44 countries helped -Long term ◦