FACTORS AFFECTING THE IMPACT OF

VOLCANOES

Why some volcanoes are hazardous than the other?

• Type of Volcanic Eruptions• Type of Volcanic Materials Ejected• Geographical Location of a Place

Types of Volcanic Eruptions

EFFUSIVE ERUPTION EXPLOSIVE ERUPTION

Eruptions are quiet Non-explosive Spew basic lava that

spreads out over large areas

Less dangerous as people rarely get killed

E.g.: The Kilauea volcano in Hawaii.

Eruptions are loud & Violent

Explosive because of pressure building up in the magma

Eject acid lava, ash, gases & rock fragments

Dangerous as the materials can rain down on settlement

E.g. The Krakatau in Indonesia

LAVA FLOWS◦ Less dangerous to

humans◦ Travel slowly &

people are able to avoid them

◦ However, death may occur if the lava flows block people’s escape routes.

ASH –(smallest & finest fragments of lava or rock)◦ Ash in the air can

block sunlight & reduce visibility.

◦ Disrupt people’s activities.

◦ Cause asthma & coughs

Types of Volcanic Materials

VOLCANIC BOMBS◦ Large fragments of

volcanic rock. Semi-solid or partially molten

◦ Cause severe injuries & death to humans.

POISONOUS GASES◦ Trapped in magma are

released into the atmosphere when volcanoes erupt explosively

◦ Carbon Dioxide: can harm vegetation & air that has more CO2 can cause death in people & animals

◦ Sulphur Dioxide: contribute to the formation of acid rain. Causes skin, eye, nose & throat irritations.

PYROCLASTIC FLOWS◦ Gases mix with

volcanic materials◦ Fall down very quickly

down the slopes (up to 100km/h)

◦ Temp: 200 °C–700 °C◦ They will burn, knock

over or bury anything in their path

LAHAR (mudslide)◦ Occurs when water

mixes with ash & rock fragments.

◦ Flow very fast◦ Very destructive and

can bury anything in their path.

Volcanoes mostly located at plate boundaries◦ Countries that are in close proximity such as

Indonesia & Philippines will experience more impacts compare to Brunei.

The impact is greater if the volcanoes are located in close proximity to settlements.◦ Densely populated settlements will be at risk.

Geographical Location of a Place