Eruptions Involving External Water

Question 1

Phreatomagmatic Volcanism

Answer 1

Volcanic eruptions resulting from interaction between magma and water.

This includes groundwater, shallow standing water, ice

Question 2

Fragmentation

Answer 2

Shattered magma driven by interacting with external water.

Question 3

Littoral Explosions

Answer 3

From lava entering body of water

Pu’u Hou (dark, mafic material from Littoral piled)

Question 4

Surtseyan Eruptions

Answer 4

Interacting through body of standing water.

Tuff cones

Question 5

Maar Eruptions

Answer 5

Lava interacting through groundwater

Question 6

What eruption types fall under Mafic Phreatomagmatic Volcanism?

Answer 6

Maar, Surtseyan, Littoral

Question 7

What controls explosivity (efficiency of fragmentation) of Phreatomagmatic Volcanism?

Answer 7

1. Magma Composition & Viscosity
2. Water to Magma Ratio
3. Pressure in System from rocks or water

Question 8

What is the ratio of Water to Magma for a Phreatomagmatic Volcanism?

Answer 8

Dry Phreatomagmatic - 0.2 to 1.1 mass ratio

Wet Phreatomagmatic - 5.0 to 50 mass ratio

Surtseyan Eruptions are in between the two from 0.8 to 5.0

Question 9

What magma types can interact with external water?

Answer 9

All but more likely more Mafic (silica)

Question 10

How are eruptions involving external water studied?

Answer 10

Look at products of past eruptions to determine conditions that supported explosive behavior.