Tectonics: 1.5 - If It Congo Wrong

Question 1

Lahars

Answer 1

Water mixed with volcanic deposits that flow rapidly along valleys

Can carry large amounts of material

Secondary hazard

Question 2

Lava flows

Answer 2

Magma that has reached the surface and flows

Question 3

Viscosity of lava

Answer 3

Viscosity depends on the amount of silicon dioxide (SiO2) in lava
Basaltic lava - 50% silica = low viscosity (forms shield volcanoes)
Andesitic lava - 60% silica
Rhyolitic lava - 70% silica = high viscosity (forms composite volcanoes)

Question 4

Gas/steam emissions

Answer 4

H2O vapour -> heavy rainfall -> lahars

Sulfur dioxide leads to acid rain

Fluorine gas is poisonous in high concentrations, contaminates farmland and water supplies

Question 5

Tephra falls (ash falls)

Answer 5

Ash is carried into the atmosphere, potentially transboundary

Most falls locally causing roofs to collapse, breathing difficulties, and buries crops and vegetation

Question 6

Pyroclastic flows

Answer 6

Magma stuck in the vent of a volcano explosively bursts out to eject a dense mixture of hot gases and pyroclastic material

Can reach temperatures up to 1000°C
Leaves volcanic deposits (ignimbrite) 200m thick

Question 7

Jokulhlaup

Answer 7

Flood of meltwater from ice cap or glacier due to a volcano erupting underneath

Secondary hazard

Warm water melts through ice, and carries glacial moraines (dirt and rocks) and blocks of ice that are deposited in lowland areas valleys