Volcanoes and Earthquakes

Question 1

How are volcanoes formed?

Answer 1

Volcanoes are formed by:

• subduction
• rifting
• hotspots

Question 2

What is subduction?

Answer 2

Subduction is the downwards and sideways movement of the edge of a plate of the earth’s crust.

Question 3

What is rifting?

Answer 3

A rift is a linear zone where the lithosphere is being pulled apart.

Question 4

What are hotspots?

Answer 4

Hot spots are placed within the mantle where rocks melt to generate magma.

Question 5

Define a Shield Volcano (Basaltic)

Answer 5

Shield volcanoes have runny magma and have gentle eruptions.
They form when layers of lava accumulate over time.
Eruptions are slow and non-explosive.

Question 6

Define a Cone Volcano (Andesitic)

Answer 6

Cone volcanoes have sticky lava and have more explosive eruptions.
They are formed when lava is ejected high into the air and piles up around the vent

Question 7

Define a Dome Volcanoe (Rhyolitic)

Answer 7

Dome volcanoes are the most dangerous. The lava is sticky molten rock. Magma often blocks the vents, causing pressure to build up, leadings to explosive eruptions

Question 8

Explain how and why magma can erupt from a volcano

Answer 8

Volcanoes erupt because of the density and pressure of the magma.
Volcanoes can either erupt in an explosive or effusive way.

Question 10

What causes earthquakes?

Answer 10

Earthquakes are caused by sudden movements in the tectonic plates

Question 11

What are the ways the strength of an earthquake can be measured?

Answer 11

The Mercalli Intensity Scale: 1 (not felt) to 12 (widespread devastation)

The Richter Scale:
An increase of 1 indicated 10 times more movement, and 30 times more energy

Question 12

How do mid-ocean ridges form?

Answer 12

When plates in the ocean are pushed together

[Convergent plate boundary]

Question 13

How are oceanic trenches formed

Answer 13

When two plates separate or diverge

[Divergent plate boundary]