Volcanic Eruptions

Question 0

How does oceanic and continental crust colliding cause volcanoes?

Answer 0

Crust at ocean floor is denser than crust below continents
Collision = dense ocean plate is forced underneath less dense continental plate - subduction.
Oceanic plate cooler at edges so sink and pull the plate down
As oceanic plate forced down it melts and starts to rise - molten rock forms volcanoes

Question 1

How are volcanoes formed?

Answer 1

Magma (molten rock) from the mantle emerges through earths crust - below surface called magma
- above surface called lava

Question 2

What is igneous rock?

Answer 2

Cooled and solidified molten rock

Question 3

How can igneous rocks be different?

Answer 3

Depends on how quickly rock cools and composition of magma

• some volcanoes produce iron rich basalt - runny lava, fairly safe!
• silica rich rhyolite - thick and explosive! Dangerous!

Question 4

How do geologists predict volcano eruptions?

Answer 4

Study magma movements

Tricky to predict accurately but saves lives