Volcanic Hazards - DRRR 4Q

Volcano

A rupture in the Earth's crust.

Magma

Molten rock found within Earth.

Lava

Molten rock released from Earth's mantle.

Magma chamber

Large underground pool of magma within the volcano.

Crater

The opening at the top of a volcano.

Main Vent

Channel magma flows through to get to the surface.

At least 50

How many volcano eruptions happen each year?

Destructive plate margin/Convergent plate margin

The oceanic plate and continental plate move towards each other. The oceanic plate sinks under the continental plate, melting down into the Earth's mantle which releases gases that make their way through the crust above and erupt through the surface.

Constructive plate margin/Divergent plate margin

The two plates move apart. Overtime, this allows magma to rise up within the Earth, which fills the gaps created by the plates moving away from each other.

Pacific ring of fire

75% of the world's active volcanoes are located here.

Hotspot

These are columns of rising mantle materials that begin to melt as they rise to lower pressure and shallower depths.

High pressure buildup

When does an eruption take place?

Viscosity

A liquid's resistance to flow.

Composite volcano/Stratovolcano

Found on destructive plate margins and has a distinct conical shape. It has viscous, acidic lava, violent eruptions, and steep sides.

Shield volcano

Found at constructive plate margins or at hotspots and has gentle sloping sides. It has runny, non-acidic lava, and less violent eruptions.

Lava flow

It is a mass of magma that flows down the slope (at a rate of 3km per day or 45km per hour) of a volcano.

Volcanic gases

Gases emitted by a volcano that include water vapor, carbon dioxide, sulfur dioxide, and hydrogen halides.

Pyroclastic flow

Hot, dry masses of volcanic fragmented materials that move along a slope. It is faster than lava flow. Ashy and grey at day, and glowing hot red at night.

Tephra falls

Showers of fine to coarse-grained volcanic materials and other airborne products of a volcanic eruption. Can reach several 100 kilometers away as it is carried by the wind.

Less than 2mm

Ash in diameter.

2-64mm

Lapilli in diameter.

More than 65mm

Blocks, ash bombs, and ballistic projectiles in diameter.

Ballistic projectile

It is a type of tephra fall wherein rocks are released into the air by an erupting volcano. It can land within 2km of the vent but can travel as far as 5km or further if the eruption is very explosive.

Lahar

Flowing mixture of volcanic debris and water.

Primary or hot lahar

Associated directly with volcanic eruption.

Secondary or cold lahar

Caused by heavy rainfall.