Impacts of hazards (volcanoes)

Question 1

Tephra

Answer 1

Any type and size of rock fragment that is forcibly ejected from the volcano and travels and airborne path during an eruption (including ash and volcanic bombs).

1991 Mt. Pinatubo, Philippines
○ Emitted huge amounts of ash
○ Buried more than 180km2 of forests in 25cm of ash
○ Destroyed about 800km2 of rice, affecting livelihood of farmers (no crops to sell - no incomes
○ Seven airports in the Philippines had to be closed due to many flights being cancelled.
○ Planes were also damaged.

Question 2

Volcanic gases

Answer 2

Volcanic eruptions can release large amounts of toxic gases such as sulfur dioxide and carbon dioxide. When magma rises towards the Earth’s surface, the pressure exerted on the magma decreases, allowing dissolved gases in the magma to expand and become less dense, which eventually escapes during an eruption.

1979 Dieng volcano, Indonesia
○ Released deadly amounts of CO2 and killed about 150 people.

Question 3

Lava flow

Answer 3

Lava flows are extremely hot and can travel over some distances away from the volcano. Can burn people and objects in its path.

2018 Kilauea volcano, Hawaii.
○ Far-reaching lava flows destroyed more than 600 homes.
○ Destroyed huge forests and ecosystems
○ Telephone and power lines were destroyed, causing widespread communication outages.

Question 4

Pyroclastic flow

Answer 4

Pyroclastic flow is a hot cloud of gas, ash, and rocks travelling down the slopes of a volcano at great speeds and high temperature. Usually travels several km away from the volcano.

2010 Mt. Merapi, Indonesia
○ Blasted a series of pyroclastic flows down the slopes of volcanoes, which were inhabited by many villagers
○ About 350 villagers were killed due to burns and blast injuries
○ Huge forest areas were destroyed.

Question 5

Lahars

Answer 5

Lahars are mudflows comprising water and volcanic ash. Lahars travel at high speeds to places far away from the volcano.

1985 Nevado Del Ruiz, Colombia
○ Meltwater from surrounding snow and ice mixed with ash and rocks to form lahars which are fast-moving, and buried more than 20, 000 people in the nearby town within seconds.
○ Rivers were filled with mud from the lahars, killing many fish.

Question 6

Volcanic landslides

Answer 6

Volcanic landslides are blasts from an eruption that trigger the downward movement of thousands of solidified lava layers and loose tephra. Volcanic landslides have high velocity and great momentum, which allow them to travel far distances.

1980 Mt St. Helens (USA)
○ North face of the cone collapsed, causing volcanic landslides that travelled as far as 23km from the volcano
○ Destroyed huge areas of land and killed many wildlife.