Hazards

Question 1

Hazard

Answer 1

A natural event becomes a hazard when it poses a threat to life, health, property of the environment.

Question 2

Pyroclasric flow ?

Answer 2

Ash gas, volcanic bombs
Destructive plate boundary
Biggest killer - Mount St. Helens - bulge then exploded laterally.
6,500 km pyroclastic flows.

Question 3

Pyroclastic deposits

Answer 3

Tephra- ash particles - mount pinatubo.

Question 4

Lava flows

Answer 4

• move very slowly from shield volcanoes.

- Hawaii - move timber houses because so slow moving

Question 5

Basaltic magma

Answer 5

Low silica, low gas, low viscousity, (runny) , gas bubbles easily expand on way up.
Form at constructive or oceanic hot spot.
Lava is slow.

Question 6

Andeisitic

Answer 6

High silica, high gas, high viscousity
Wet partial melting of subduction plates.
Destructive plate margin and island arc. ( Montserrat)
Pyroclastic flow, lahar, gas emitted.
Steep sided strato volcanoes
Andeisitic lava often solidifies before reaching surface, leading to build up of pressure - very explosive.
Calderas - build up of gases becoming extreme and huge explosion removes summit of cone, leaving opening several km side in diameter.

Question 7

Rhyolitic

Answer 7

High silica, high gas, high viscousity. Continental hotspot, pyroclastic flow. W

Question 8

Style of volcanic eruptions

Answer 8

Fissure - line of weakness, basaltic magma seen in Iceland.

Shield/ Hawaiian - Molten lava eruption from lake, little tephra, shield volcanoes.

Vulcanian/ strata or composite volcano, layers of ash and lava, destructive plate boundary.
Andesitic magma - very viscous, blocks funnel, high gas content, high silica produce pyroclastic flow.

Pelean or acid of dome volcanoes
Very viscous results in blockage of main vent, lava charged with gas escapes from weak points.