1. Restless Earth

Question 1

What is the Crust?

Answer 1

The crust is the top layer of the Earth. It is made from thin layers of tectonic plates.

Question 2

What are the different types of crust?

Answer 2

Continental Crust
• made of old rock, e.g granite
• 20-75km thick

Oceanic Crust:
•mainly young basaltic rock
•5-10km thick
•temperatures up to 1200°C

Question 3

What is the Earth made up of?

Answer 3

The Earth is made up of several layers.

Question 4

What is the Mantle?

Answer 4

The mantle is the second layer of the earth.
•divided into solid upper part and semi-liquid lower part
•temperature up to 5000°C

Question 5

What is the Core?

Answer 5

The centre of the earth.
•outer core is liquid
•inner core is solid
•alloys of nickel and iron at 4000°C

Question 6

How do convection currents cause plate movement?

Answer 6

1. The core heats the molten rock in the mantle to create a convection current
2. Heated rock from the mantle rises to the Earth’s surface
3. At the surface the convection current moves the tectonic plates in the crust
4. Molten rock cools and flows back to the core to be reheate

Question 7

What is the difference between continental and oceanic crust?

Answer 7

Continental crust is thicker but less dense than oceanic crust.

Question 8

What are the different types of plate boundaries?

Answer 8

• destructive plate boundaries
• constructive plate boundaries
• conservative plate boundaries
• collision plate boundaries

Question 9

Describe destructive plate boundaries + give an example

Answer 9

Example: Nazca Plate and South American Plate
•Two plates collide, one plate flows beneath the other (subduction)
•Many earthquakes and volcanoes

Question 10

Describe constructive plate boundaries + give an example

Answer 10

Example: Eurasian and North American plates

•Rising convection currents pull crust apart forming volcanic ridge, e.g Mid-Atlantic Ridge

Question 11

Describe conservative plate boundaries + give an example

Answer 11

Example: San Andreas Fault, California
•Two plates slide past each other
•Earthquakes

Question 12

Describe collision plate boundaries + give an example

Answer 12

Example: Indo-Australian and Eurasian plates
•Two continental plates collide and the two plates buckle
•Many earthquakes

Question 13

How is a tsunami formed?

Answer 13

A tsunami can be triggere when an earthquake or a volcanic eruption happens at sea. The movement of the plates makes all of the water on top of this part of the seabed rise up. This creates two blocks of water which move in opposite directions, away from the epicentre, as huge waves.

Question 14

Describe a shield volcano

Answer 14

• they are found on constructive plate boundaries
• are formed by eruptions of thin, runny lava which flows a long way before it solidifies
• have gently sloping sides and a wide base
• contains basaltic magma which is very hot with low silica and gas content
• erupt frequently but not violently

Question 15

Describe a composite volcano

Answer 15

• are found on destructive plate boundaries
• are formed by eruptions of viscous, sticky lava and ash that don’t flow far
• have steep sloping sides and a narrow base
• made up of layers of thick lava and ash
• contain andesitic magma which is less hot but contains lots of silica and gas
• erupt infrequently but violently, including pyroclastic flows (mixes of ash, gases and rock)

Question 16

How is the Earth’s core heated?

Answer 16

by radioactive decay

Question 17

What are the primary impacts of earthquakes?

Answer 17

•injured and dead trapped under rubble
•people sleeping on the streets for fear of more earthquakes
•mortuaries unable to deal with number of dead people
-mass graves dug to bury people
•phone and power lines shut down
•streets blocked by huge piles of rubble from collapsed buildings

Question 18

What are the secondary impacts of earthquakes?

Answer 18

• disease may spread
• people need to be rehoused
• cost of rebuilding things
• businesses are destroyed
• jobs are lost

Question 19

What are the different ways of measuring the magnitude (strength) of an earthquake?

Answer 19

The Richter Scale
•measures the energy released
•maximum of 10

The Mercalli Scale
•measures the effects or impacts
•is measured in roman numerals I to XII

Question 20

why is it difficult to predict earthquakes and volcanoes?

Answer 20

we do not know:
•exactly where it will happen
•how big it will be
•what other impacts it may have

Question 21

what can help us predict earthquakes and volcanoes?

Answer 21

looking out for:
•animals acting strangely/change in behavioural patterns
•an increase in gas emissions
•an increase in soil temperature
•the volcano swelling
•an increase in small earthquakes
•water in ponds getting warmer

Question 22

what is needed after an earthquake or volcanic eruption?

Answer 22

• trained volunteers to help the injured people and to clear away the debris
• clean water to prevent the spread of disease
• food because often shops, towns, roads and farms have been damaged
• radio communication because phones will often not work
• medical help to care for the injured people
• a plan to evacuate the area if needed

Question 23

how can you strengthen a building?

Answer 23

• very strong framework in skyscrapers
• strengthening walls
• making foundations from rubber and steel which can move slightly
• digging deeper foundations
• reinforce gas and water pipes so they do not break
• pendulums that swing the other way
• criss-cross structures/framework to reinforce the building
• double or triple glazed windows