Earthquakes & Volcanoes

Question 1

What are the main types of plate boundaries?

Answer 1

Main types of plate boundaries:
* Constructive (divergent)
* Destructive (convergent)
* Conservative
* Collision

Question 2

How do volcanoes form at constructive plate boundaries?

Answer 2

• Constructive plate boundaries often occur under the sea/ocean.
• Tectonic plates are moving away from each other.
• Lava rises from deep inside the Earth.
• The lava rises to fill the gap left as the plates move apart.
• It then erupts (through crack in surface).
• The lava cools and hardens, forming a new crust (oceanic - denser).
• These form shield volcanoes, which are gently sloped.

Question 3

How do volcanoes form at destructive plate boundaries?

Answer 3

• The heavier and denser oceanic plate subducts under the lighter continental plate.
• In the subduction zone, the two plates come together causing friction.
• Friction causes heat and pressure and the plate material melts, forming magma.
• The magma rises to the surface through crack in the crust.
• The cooling lava and ash build up, forming a volcano.
• Tend to form strato/composite volcanoes.

Question 4

How do volcanoes form at hotspots?

Answer 4

• At a hot spot, the tectonic plate passes over a plume of magma.
• The magma rises to the surface through cracks in the crust.
• As the tectonic plate moves slowly over the magma plume, a line of islands may form.

Question 5

How do earthquakes form at conservative plate boundaries?

Answer 5

• The plates move past each other in opposite directions or in the same direction at different speeds.
• Friction occurs causing plates to ‘stick’.
• Pressure and tension will build up.
• Pressure is released, so there is a sudden jerk.
• Seismic waves are transmitted to Earth’s surface.

Question 6

What is a collision boundary?

Answer 6

• Two plates of similar density move towards each other.
• Neither is dense enough to subduct, so the land is pushed upwards.
• This forms fold mountains.