Keywords

Chapter 2: Volcanoes (pg.17-25)

Volcano

A mountain formed by the eruption of magma on earth’s surface through a hole or vent in the earth’s crust. Eg. Mount Fuji in Japan

Lava

Hot molten rock that has erupted above the earth’s surface from a volcano or fissure.

Fissure

A long, narrow crack in the Earth’s crust though which magma or gases can rise to the surface.

Plateau

A flat-topped upland area with steep sides that forms when lava flows out of q fissure in the Earth’s crust and spreads out in layers. Eg. The Antrim Plateau

Silica

A mineral made of silicon and oxygen that is found in rocks and affects how thick or runny lava is, influencing how explosive a volcano is.

What makes a volcano violent and explosive?

If magma contains a lot of silica, a lot of gas is trapped in it. This causes a violent explosive eruption, which usually makes a typical volcanic cone-shaped mountain, Eg. Mount St. Helens in the US.

What makes a volcano less explosive?

If the magma contains less silica, less gas is trapped making it more runny like water so when it erupts it s less explosive, making a wider shield-shapes volcanic cone. Eg. Hawaiian Islands

Pyroclast/pyroclastic flow

A superheated mix of rock fragments, ash and gas that is ejected from a volcano during a violent eruption. It can travel at great speeds of 100km/h to 800km/h Eg. Mount Pinatubo, Philippines

Where do volcanoes form?

Where plates collide, where plates separate and at hot spots

Pacific Ring of Fire

The largest zone of volcanic and seismic activity caused by the collision and movements of the Pacific plate with the surrounding plates of Asia, North and South America and Australia. Over 90% of the world’s volcanoes occur here. Eg. Mount Fuji, Japan

What are the three stages of a volcano life cycle?

Active, dormant, extinct

Active volcano

A volcano that is continuously erupting. Eg. Mount Etna in Italy

Dormant volcano

A volcano that has not erupted for a long time but could erupt again at any time. Eg. Mount St Helens in the US

Extinct volcano

A volcano that has not erupted for at least 10,000 years and is not expected to erupt again. Eg. Slemish Mountain, County Antrim