Volcano

What is a volcano?

An opening in the crust where lava, ash and gases erupt.

What is magma?

Molten rock beneath Earth’s surface.

What is lava?

Magma that reaches Earth’s surface.

What is a tectonic plate?

A large moving section of Earth’s lithosphere.

What drives tectonic plate movement?

Processes in the mantle, including convection and slab pull.

What is a constructive plate boundary?

Two plates move apart and magma rises to form new crust.

What is a destructive plate boundary?

Plates converge; one may subduct beneath the other.

What happens at a collision boundary?

Two continental plates collide and fold into mountains.

What is a hotspot?

A location where hot mantle material causes volcanism away from boundaries.

What is subduction?

One tectonic plate sinks beneath another.

Why do volcanoes form at destructive boundaries?

Subduction helps generate magma, which rises through the crust.

Why do volcanoes form at constructive boundaries?

Magma rises through gaps as plates separate.

What is a composite volcano?

A steep volcano made of alternating lava and ash layers.

What is a shield volcano?

A broad, gently sloping volcano formed by fluid lava.

Why are composite volcanoes often explosive?

Viscous magma traps gases, building pressure.

Why are shield volcano eruptions often gentler?

Runny basaltic lava lets gases escape more easily.

What is a crater?

A bowl-shaped depression around a volcanic vent.

What is a volcanic vent?

The opening through which eruptive material escapes.

What is an ash cloud?

Fine rock and volcanic glass particles released into the air.

What is a pyroclastic flow?

A fast-moving, extremely hot mixture of ash, gas and rock.

What is a lahar?

A volcanic mudflow of water mixed with ash and debris.

How can volcanic ash affect transport?

It can close airports and reduce road visibility.

How can volcanic ash affect people?

It can cause breathing problems and contaminate water.

How can lava damage settlements?

It burns or buries roads, buildings and farmland.

How can volcanoes benefit farming?

Weathered volcanic material can create fertile soils.

How can volcanoes benefit energy supply?

Geothermal heat can produce electricity and heating.

How can volcanoes benefit tourism?

Scenery, hot springs and hiking attract visitors.

Why do people live near volcanoes?

Fertile soil, jobs, tourism, geothermal energy and family ties.

How can scientists monitor volcanoes?

Measure earthquakes, gas emissions and ground deformation.

Why does the ground swell before some eruptions?

Rising magma can push the surface upwards.

How do hazard maps reduce volcanic risk?

They identify dangerous zones for planning and evacuation.

How do evacuation plans reduce volcanic deaths?

They help people leave high-risk areas before eruptions.

Why can volcano predictions be uncertain?

Monitoring signals do not always lead to an eruption.

Where is Mount St Helens?

Washington State, north-western USA.

When did Mount St Helens erupt famously?

18 May 1980.

What triggered the 1980 Mount St Helens eruption?

An earthquake and landslide removed part of the volcano’s flank.

Name a major impact of Mount St Helens in 1980.

57 people died; ash and debris damaged forests and infrastructure.

What happened to forests near Mount St Helens?

The lateral blast flattened large areas of forest.

How did ash affect Mount St Helens surroundings?

Ash disrupted roads, flights, agriculture and machinery.

What was one long-term response at Mount St Helens?

Monitoring and restricted access in hazardous areas.

What is the difference between primary and secondary volcanic hazards?

Primary: lava and ash; secondary: lahars and landslides.

What is the difference between active and dormant volcanoes?

Active has erupted or shows activity; dormant is currently quiet but may erupt.

What is an extinct volcano?

A volcano not expected to erupt again.

Why does distance from a volcano affect risk?

Hazards like lava and pyroclastic flows usually affect nearer areas most.

How can heavy rainfall worsen volcanic hazards?

Rain can mix with ash to form destructive lahars.

When did Mount St Helens erupt catastrophically?

18 May 1980.

What triggered the main Mount St Helens eruption?

An earthquake and huge landslide released pressure.

How many people died in the 1980 Mount St Helens eruption?

57.

What were two effects of the Mount St Helens eruption?

Forests flattened and volcanic ash disrupted transport.

How is volcanic risk managed at Mount St Helens?

Monitoring, hazard maps and restricted access to high-risk zones.