Investigation 5 As you Read… Answers

# 1 What is the Cause of Earthquakes?

Earthquakes are caused by movement along a fracture plane in the Earth’s crust. When the rocks break, rocks on either side of the fracture plane slide past one another, and the strong vibrations that result are felt as an earthquake.

#2. How are faults and earthquakes related?

Faults are fractures in the Earth’s crust along which there has been rupture and movement in the past. Earthquakes occur when the forces that build up along faults overcome the strength of the rocks, the rocks on either side of the fault slide pass one another, and strong vibrations are generated.

#3. What is the cause of volcanoes?

Volcanoes are caused by the rising magma formed within the Earth Volcanoes are caused by the rising magma formed within the Earth. Magma rises because it is less dense than the surrounding rock. The rinsing magma does not always reach the surface, but when it does, it forms a volcano.

#4. How does gas content affect how a volcano erupts?

If the gas content of magma is low, the magma erupts gently If the gas content of magma is low, the magma erupts gently. If the gas content of magma is high, an explosive and violent eruption can occur.

#5. How is volcanism at a hotspot different fro volcanism at a mid-ocean ridge. How are they similar?

Volcanism at a hotspot can occur far from plate boundaries, where volcanism at a mid-ocean ridge occurs at a plate boundary (divergent). Both types result in the production and release of magma.

#6. Why are mountains found in regions where the lithosphere is thick?

When plates collide, the lithosphere becomes thicker When plates collide, the lithosphere becomes thicker. Because the lithosphere (continental crust) floats on the mantle, the thicker the Lithosphere (continent), the higher the mountain will be.