Tectonic Plates

Question 1

Convection current

Answer 1

• Mantle material is heated up by the core which expands and rises up and spreads out underneath the plates causing them to be dragged and move away from each other.
• Mantle material then cools slightly and sinks, dragging the plate along with it
• Mantle material is then heated up again by the core and the whole process reappears itself.

Question 2

Oceanic oceanic divergence

Answer 2

• When the 2 oceanic plates diverge, fractures are formed at the plate boundaries.
• Magma then rises from the mantle material and cools and solidify to form a mid oceanic ridge
• Various points along the mid oceanic ridge, magma continues to build up and solidify to form undersea volcanoes and eventually forms a volcanic island.

Question 3

Slab pull force

Answer 3

Subduction plates drive the downward moving portion of the convection current. Mantle material causes the upwards moving portion of the convection current.

Question 4

Continental continental divergence

Answer 4

• When 2 continental plates diverge, fractures will be formed along the plate boundaries when they are pulled apart
• The land in between the 2 continental plates sink to form a linear depression known as a Rift Valley.
• East African Rift Valley(Somalian and Nubian plate)

Question 5

Oceanic oceanic convergence

Answer 5

• When 2 oceanic plates converge and collide, the denser oceanic plate will subduction underneath the less dense oceanic plate
• A deep oceanic trench is formed at the point of subduction
• As the oceanic plates subduct underneath, it will cause the mantle material above it to melt and form magma.
• The magma rises through the crust which forms volcanoes and eventually a chain of volcanic islands is formed.

Question 6

Continental continental convergence

Answer 6

• When 2 continental plates converge, the plates are too buoyant and resist subduction
• This causes the plates to break up and slide along the fractures of the crust
• layers of rocks on the upper parts of the crust are compressed together and they fold upwards or sideways, forming fold mountains

Question 7

Oceanic continental convergence

Answer 7

• The denser oceanic plate will subduct underneath the less dense continental plate
• A deep oceanic trench is formed at the point of subduction
• Continental plates will buckle and fold to form fold mountains
• Mantle material will melt to form magma which rises through fractures to form a volcano and volcanic eruptions

Question 8

Transform plate

Answer 8

• Plates slide past each other ; results in fault lines along earth surfaces.
• As plate slide past each other, immerse stress is accumulated which is real eased in the form of earthquakes.

Question 9

Fold mountains

Answer 9

• Formed along convergent plate boundaries where plates move towards each other and collide
• Compressional forces creates immerse pressure which causes the plates to buckle and fold called folding
• Upfold is anticline; downfold is syncline

Question 10

Tsunami formation

Answer 10

• formation of a tsunami starts when the seismic energy of an offshore earthquake forces out a mass of seawater
• Tsunami waves may start at heights of less than 1m and width of 100-150km and speeds up to 800km/h and may pass undetected
• On reaching shallower waters, greater forces will cause it to slow down and increase in height
• On the point of impact on the coast, the tsunami waves could be travelling at 30-50km/h and heights up to 15m
• Sometimes the sea recedes before the tsunami reaches the shore.The sea recedes because water first rushes to fill up the void in the sea floor. Water is then forced out again soon afterwards, resulting in a tsunami

Question 11

Impacts of tsunami

Answer 11

1. Disruption of services-water and electricity
   ~Kobe Japan 1995, damaged pipes and transmission lines which disrupted electricity and water supplies to about a million of Kobe city’s population of 1.4 million people
2. Landslides- rapid downward movement of soil, rock and vegetation
   ~ Peru 1970, earthquakes off the shores of Peru destabilise the slopes of Mount Huscarán and triggered a massive landslide which travelled more than 160km/h and completely flattened out the town of Ranrahirca in a matter of seconds. The death toll was more than 180 000 and only 200 people survived the disaster

Question 12

Impacts of tsunami (2)

Answer 12

-Destruction of properties
~Tōhoku Japan 2011 , extensive structural damage resulted in hundreds of thousands of people being forced from their homes.
-Destruction of infrastructure
-loss of lives

Question 13

Rift Valley

Answer 13

• formed at divergent plate boundaries, where plates are pulled apart to give to faults which are fractures in the rocks
• tension always from these movements results in parts of the crust being fractured called faulting
• sections of the crust extends along daily lines, tensions forces cause a central block of land to subside between parallel faults, forming a Rift Valley

Question 14

Block mountains

Answer 14

• When tension always forces causes the land masses surrounding a block of land to subside, a block of land is formed between parallel faults
• A block mountain is a block of land with steep slopes left standing higher than the surrounding land.

~Vosges in France and Black Forest in Germany
-separated by Rhine valley, divergence of Eurasian plate and north American plate

Question 15

Extent of earthquake

Answer 15

• population density
• level of preparedness
• Distance from epicentre
• Time of occurrence
• Type of soil

Question 16

Volcano formation

Answer 16

• as more magma seeps into the magma chamber, the amount of pressure builds up giving rise to a volcanic eruption
• When a stratovolcano erupts, pyroclasts are released. The force of a volcano depends on the amount of pressure in the volcanic chamber
• A new eruption of lava covers up the pyroclasts building up the volcano
• lava build up around the vent solidifying to form a small volcanic cone
• During the formation of the volcano the vent may become blocked. This forces the magma to find a new exit route to the surface. A secondary cone of newer volcanic material will be formed
• The summit of the volcano may be blown off during an explosive eruption.the sides of the volcano may collapse due to the loss os structural support. A large depression known as a caldera is formed

Question 17

Earthquake

Answer 17

• Vibrations in the earths crust caused by the sudden release of stored energy in rocks found along the fault lines
• Occurs when there is plate movements along plate boundaries, due to the friction between moving plates, plate movements cause a slow build up of stress found on either sides of the faults
• when rocks can no longer withstand the increasing strength, they may suddenly slip a few metres, causing an earthquake

Question 18

Extent of earthquake

Answer 18

• Population density
• level of preparedness
• distance from epicentre
• time of occurrence
• type of soil