Volcanoes

Question 1

What are phreatic eruptions

Answer 1

Steam-driven explosions when water enters under the surface and is heated by magma.

Question 2

Decompression melting

Answer 2

solid mantle moves up to lower melting and pressure area. when the pressure decreases the bonds between particles can be broken down. It is common with subduction zones and divergent boundaries.

Question 3

Volatiles

Answer 3

1 Water (also CO2 and sulphur dioxide)

Question 4

Heat / Melt assimilation

Answer 4

Rising magma from the mantle heats and melts foreign rocks and materials around it.

Question 5

Pyroclastic density currents

Answer 5

Steam and ash emitted from the volcano is side-swept by wind, but tephra (the big chunks of rock and material) collapses and forms pyroclastic density currents that hang low to the ground and are the most hazardous.

Question 6

Landslides occur with which type of volcano? (not form but physical nature)

Answer 6

Tall, weak, and steep

Question 7

How does magma make landslides?

Answer 7

Magma produces volatiles like water which change the chemical makeup of material around the eruption resulting in mud etc.

Question 8

Lahar vs. a Landslide

Answer 8

Landslides are from the change in moisture around the volcano and its debris, the lahar is formed when rain or snow occurs during the eruption or after and mixes with any ash and debris caused by the eruption.

Question 9

What are the two types of volcanic gases?

Answer 9

Laze: lava/haze which is a mix of hydrochloric gas, steam and volcanic gas. Causes a type of acid rain and air pollution. usually occurs when molten lava enters cold oceans.

Vog: Volcanic fog which is a mix of sulphuric gas and for example ash, it mixes dust and gas.

Question 10

Example of a laze or vog

Answer 10

Laki, Iceland (1783)
released a hydrofluoric acid which killed livestock and caused a famine

Lake Nyos (1986)
emitted co2 and it outweighed oxygen killing livestock and people.

Question 11

Explain the Pinatubo event

Answer 11

In April 1991 there was phreatic emission from the area, so they added seismographs at the base. They began to survey the past activity and from this predicted that the volcano would erupt on June 6 with a 10-day window, they involved the media and emphasized the level of eruption. evacuated 5000 people within a 10km radius of the volcano. On June 8th ash-laden steam clouds were spewing out and then the next day there were two eruptions. Some people didn’t want to evacuate. It’s a convergent boundary between the Eurasia plate and the philippine mobile belt which caused subduction.

Question 12

What type of volcano is a mantle plume associated with?

Answer 12

Mantle plumes are hot spot volcanoes, which do not occur because of plate tectonics.

Question 13

Three types of assessment for volcanic activity

Answer 13

GPS
Seismographs
Infared

Question 14

Signs of volcanic activity

Answer 14

Gas leaks
Bulging
shaking 
drop in seismic activity
big buldge
phreatic emissions