Tectonic Plates, Plate Boundaries And Structure Of The Earth

Question 1

Layers of the earth in order from inside to outside and their properties

Answer 1

Inner core: 1250km, over 5000°C, Iron and nickel, lots of pressure so solid
outer core: Semi liquid iron, 2300km thick, earth’s magnetic field, 3700-5000°C
mantle: Thickest layer, moves in convection currents, semi-molten (semi-liquid) rock that can flow, 1000-3500°C
crust: Thinest layer (5-70km) and is solid rock

Question 2

What are plate tectonics?

Answer 2

• The Earth’s crust is made up of a number of large plates that are
  moving in constant, slow motion.
• Convection currents in the mantle move the plates. The source of heat
  driving the convection currents is radioactive decay which is happening
  deep in the Earth.
• The ocean floors are continually moving, spreading from the centre
  and sinking at the edges.
• At the edges of these plates (plate boundaries) earthquakes and
  volcanoes occur.

Question 3

Evidence to support plate tectonic theories

Answer 3

• Some continents fit together like pieces of a puzzle, implying they were once one big continent- Pangea (eg: Africa and India)
• Convection currents- movements of volcanic rock in the mantle. The magma rises to the crudt where they cool and sink again. This process was powerful enough to move the continents
• Similar fossils were found in different continents. Such species could not have crossed between the continents therefore the continents must have once been together. (Eg: Mesosaurus)
• Similar patterns of rock are found on different continents and when the continents are put together, these patterns almost perfectly come together (Eg: Coal in antartica)

Question 4

Explain why volcanoes and earthquakes are found along plate boundaries

Answer 4

• Earthquakes are found along plate boundaries because as the plates move past eachother, friction is created until the force is released causing an earthquake
• Volcanoes are found along plate boundaries when convergent plates move towards eachither and the oceanic plate sinks below the continental plate as it is thiner and more dense. Fold mountains form as the two plates clash and magma builds up under, eventually escaping through the mountains forming volcanoes.

Question 5

Explain why composite volcanoes and earthquakes occur on divergent/ constructive plate boundaries

Answer 5

The tectonic plates are moving away from one another. The Earth’s crust is pulled apart to create a new pathway for rising hot magma to flow on to the surface. The movement of the plates over the mantle can also cause earthquakes to occur.

Question 6

Subduction zone

Answer 6

where one plate is forced downwards below another plate and grinds past it causing huge amounts of friction and heat.

Question 7

Oceanic crust

Answer 7

plate that is made up of more dense rock. It sinks easily due to its density and is constantly created at boundaries. It is ‘young/new rock’ and forms our ocean bed.

Question 8

Destructive/ convergant plate boundary

Answer 8

where two plates are moving towards each other, one of which is continental crust and one is made of oceanic crust. The oceanic plate subducts under the continental plate as it is denser.

Question 9

Continental crust

Answer 9

this is a plate that is made up of less dense rock. Because it is less dense it doesn’t sink. It is exceptionally old and makes up our land surfaces

Question 10

Plate boundary

Answer 10

where two very large crustal plates meet on the earth’s surface. Earthquakes and volcanoes happen here.

Question 11

Fold mountain

Answer 11

are large mountain ranges formed by the collision and ‘folding’ of two plates as they plates continually push into one another.

Question 12

Ocean trench

Answer 12

a particularly deep point of the ocean bed where the oceanic and continental crust have dragged each other downwards.

Question 13

What is a conservative plate boundary? (give 1 example)

Answer 13

Plate boundaries where two plate are either slipping past each other in opposite directions or at different rates in the same direction. (Eg: San Andreas Fault line, California)

Question 14

What is a divergant/ constructiveplate boundary?

Answer 14

When two tectonic plates are moving appart from eachother due to convection currents.

Question 15

What is a collision plate boundary?

Answer 15

When two continental plates move towards eachother with similar densities, often creating fold mountains

Question 16

Explain why human and physical factors cuased the Haiti earthquake to be so destructive

Answer 16

Human- None of the Haiti residents were prepred as they had very little warning due to the high levels of poverty in the area. The population was also extremelly dense (10 million in Haiti) meaning the earthquake directly impacted more people. Buildings built poorly so they easily collapsed (poor quality concrete, no licencing requiremnts for engineers, builders or architects, no seismic design), very little development meaning they didn’t have the technology to sense/ predict earthquakes or the technology to send warnings
Physical- The epicentre was very close to the main city, Port-au-Prince, the focus was very close to the surface meaning the seismic waves were more poeerrul, very high magnitude

Question 17

Explain the impacts and responses from the Hait case study

Answer 17

The earthquake left 220,000 dead, over 300,000 injured and more than 1.5 million people homeless, resulting in an immense humanitarian crisis. An already severe situation deteriorated in the first year, with tropical storms causing more destruction and a cholera outbreak leaving thousands more dead. The World Bank provided extra funding of $100 million to support recovery and reconstruction in Haiti. UNICEF made an emergency appeal for assistance to aid the victims.

Question 18

What caused the Indian Ocean Tsunami- 2004 and what were the impacts?

Answer 18

On a plate boundary between the Eurasian and Indo-Australian plate, destructive (subduction occurs), and over many years, tension builds. An earthquakeoccurs and water is displaces upwards at the epicentre. In deep water, the waves are low and fast. As the waves approach shallow water they slow, grow taller and converge together. Waves spread out from the epicentre across the Indian Ocean and affect 12 countries and waves break onto the coastline at about 20-30m in height, killing more than 250,000 people in a single day, and leaving more than 1.7 million homeless.