Tectonic plates

Question 1

Describe the full definition of the internal structure of the earth

Answer 1

Crust(Continental/Oceanic): Less than 1% of earth vol

• Oceanic
  
  • Crust thickness: Thin (5-8km)
  • Denser rock
  • Younger rocks (less than 200 mil years)
• Continental Crust
  
  • Thicker (35-70 km)
  • Less dense rock
  • Mostly older rocks (recent to 4 bill years)

Mantle: 80% of the earth’s total volume

• Made up of mostly solid rocks
• Temperature between 800-3000 degrees
• Upper mantle/Lower mantle
• 2900 km thick

Core:

• The total thickness 3500km
• Temperature between 3000-5000 degrees
  
  • Inner core: solid, 1400km thick
  • Outer core: liquid, 2100km thick

Question 2

Explain why do tectonic plates move?

Answer 2

• Due to convection current
• Magma in the mantle is heated by the core, expands. rises and spread beneath the tectonic plates.
• Hence, this pulls the plates apart at the divergent plate boundary.
• The magma cools and sinks slightly.
• Slab-pull force occurs when the denser oceanic plates subduct beneath the less dense oceanic plate and pulls the rest of the subducting plate into the mantle under its own weight.
• Magma is reheated near the core, repeating the heat cycle movement in the mantle.

Question 3

Describe a mid-oceanic ridge

Answer 3

A ridge of new ocean floor/underwater mountain range that is caused by two oceanic plates moving away from one another
- e.g Mid-Atlantic Ridge

Question 4

Describe Volcanic islands

Answer 4

A range of underwater volcanoes that grow above sea level and are found along the mid-oceanic ridge
- Mariana islands

Question 5

Describe Block Mountains

Answer 5

A block of land with steep slopes that are left standing higher than surrounding land.
-Vosges mountain in France

Question 6

Describe Rift valley

Answer 6

A valley with steep sides

- East African Rift

Question 7

Describe Fold mountains

Answer 7

Compression of rocks when the continental plates move towards one another and collide. Thus, this causes the layers of rocks to buckle and fold upwards
- The Himalayas

Question 8

Describe Oceanic Trench

Answer 8

A depression in the seafloor when the denser oceanic plate subducts beneath the less dense oceanic/continental plate.
- Mariana Trench

Question 9

Describe Volcanoes

Answer 9

A landform formed by magma ejected from the mantle onto the earth’s surface

Question 10

Oceanic-Oceanic Divergence explanation

Draw and annotate

Answer 10

• Convection current in the mantle causes the NA and Eurasian oceanic plates to diverge.
• Tensional forces cause fractures to form at the plate boundaries.
• Magma rises at the zone of divergence, cools, and solidifies to form a ridge of seafloor, known as a mid-oceanic ridge(mid-Atlantic ridge).

Question 11

Continental-Continental Divergence explanation

Draw and annotate

Answer 11

• Convection current in the mantle causes Somalian and Nubian continental plates to diverge.
• Tensional force causes the two plates ofthick continental crust to be pulled apart, it is stretched thin, causing fractures and normal fault lines to form in the crust.
• When the central block of land between normal fault lines sinks due to tensional force, it forms a rift valley with steep sides (East African Rift Valley)

Question 12

Continental-Continental Convergence explanation

Draw and annotate

Answer 12

• As two Eurasian and Indian continental plates converge, they collide and push against but resist subduction as both plates are too buoyant to subduct.
• Plates break and slide along fault lines in the crust.
• Compressional force causes layers of rocks on the upper crust to buckle and fold, forming fold mountains(Himalayas).
• The folding process gives rise to a series of anticline and syncline evident in a fold mountain.

Question 13

Oceanic-Continental Convergence explanation

Draw and annotate

Answer 13

• Convection current in the mantle causes the dense Nazca oceanic plate to subduct under the less dense South American continental plate at the convergent plate boundary.
• A deep oceanic trench(Peru-Chile Trench) is formed at the point of subduction.
• The subducting plate melts under high temperature in the mantle to form magma. Magma rises through fractures in the crust, and reaches the earth’s surface as lava.
• With each volcanic eruption, lava cools, solidifies, and accumulates to form continental volcanic arcs.
• Compressional force causes layers of rocks to buckle and fold, forming fold mountains on the South American continental plate(Andes fold mountain).

Question 14

Oceanic-Oceanic Convergence

Draw and annotate

Answer 14

• Convection current in the mantle causes the dense oceanic Pacific plate subducts under the less dense oceanic Philippine plate at the convergent plate boundary.
• A deep oceanic trench is formed at the point of subduction(Mariana Trench),
• The subducting plate melts under high temperature in the mantle to form magma. Magma rises through fractures. With each volcanic eruption, the magma cools, solidifies, layers to form volcanic island arcs(Mariana Islands)

Question 15

Transform plate boundaries

Answer 15

• When two plates, Oceanic Pacific Plate and North American Plate slide past one another in the opposite direction along fault lines at transform plate boundary(San Andrea Fault Line), no features or landforms are formed.
• As plates slide past each other, friction and stress build up on the rocks along the fault lines.
• When the rocks can no longer withstand the increasing pressure, they slip, releasing stored energy in the form of seismic waves, triggering earthquakes.