Volcanic eruptions

Question:

How are volcanic eruptions related to properties of magma?

Background:

The table has data for 16 volcanic eruptions. The eruptions are rated by eruptive violence, magma viscosity, silica content in the magma and water content in the magma. Silica (plural silicates) are minerals that are compounds of silicon and oxygen. On scatter plot 1 you will plot data referencing the silica content. The water content of a magma will vary based upon the source of the rocks that melted to form the magma. On scatter plot 2, the water content data will be plotted.

Scatter Plot 1 (SILICA SiO₂) Procedure:

From the table, find the eruptive violence and magma viscosity for a volcanic eruption. Locate the appropriate square on the scatter plot y-axis for the eruptive violence and the square on the x-axis for the magma viscosity. In this intersection place a H or L depending if the eruption's magma silica content was high or low.
As an example, Mt. Etna in Sicily has been plotted for you. This eruption had a moderate eruptive violence and medium magma viscosity. The silica content of the magma was high so a H was placed in the center square of scatter plot 1.
Repeat step 1 for all the eruptions listed in the table.

Scatter Plot 2 (WATER H₂O) Procedure:

As you did for scatter plot 1, after locating the appropriate square on the y-axis for the eruptive violence and the square on the x-axis for the magma viscosity, plot a H or L depending on the eruption's water content.
Mt. Etna in Sicily has again been plotted for you. An L was plotted because the magma's water content was low.
Repeat step 1 for all the eruptions listed in the table.

Eruption Data Table

Volcano Location Year Type Eruptive Violence Magma Viscosity Magma SiO₂ Content Magma H₂O Content Eruption Products

Etna, Sicily 1669 Strato moderate medium high low lava,ash,cinders

Tambora, Indonesia 1815 Strato (caldera) high high high high ash,cinders,gas

Krakatoa, Indonesia 1883 Strato (caldera) high high high high ash,cinders,gas

Pelle, Martinique 1902 Strato (dome) high high high high gas,ash

Vesuvius, Italy 1906 Strato moderate medium high low lava,ash

Lassen, CA 1915 Strato (cinder) moderate high high low ash,cinders

Mauna Loa, HI 1933 Shield low low low low lava

Parcutin, Mexico 1943 Cinder moderate medium high low ash,cinders

Surtsey, Iceland 1963 Shield moderate low low high lava,ash

Kelut, Indonesia 1966 Strato (cinder) high high high high gas,ash

Arenal, Costa Rica 1968 Strato high high high low gas,ash

Helgafell, Iceland 1973 Shield moderate medium low high lava, ash

Mt. St. Helens, WA 1980 Strato high high high high gas,ash

Laki, Iceland 1983 Shield moderate medium low high lava,ash

Kilauea Iki, HI 1987 Shield low low low low lava

Fernandina, Galapagos 1994 Shield low low low low lava

Volcano Location	Year	Type	Eruptive Violence	Magma Viscosity	Magma SiO₂ Content	Magma H₂O Content	Eruption Products
Etna, Sicily	1669	Strato	moderate	medium	high	low	lava,ash,cinders
Tambora, Indonesia	1815	Strato (caldera)	high	high	high	high	ash,cinders,gas
Krakatoa, Indonesia	1883	Strato (caldera)	high	high	high	high	ash,cinders,gas
Pelle, Martinique	1902	Strato (dome)	high	high	high	high	gas,ash
Vesuvius, Italy	1906	Strato	moderate	medium	high	low	lava,ash
Lassen, CA	1915	Strato (cinder)	moderate	high	high	low	ash,cinders
Mauna Loa, HI	1933	Shield	low	low	low	low	lava
Parcutin, Mexico	1943	Cinder	moderate	medium	high	low	ash,cinders
Surtsey, Iceland	1963	Shield	moderate	low	low	high	lava,ash
Kelut, Indonesia	1966	Strato (cinder)	high	high	high	high	gas,ash
Arenal, Costa Rica	1968	Strato	high	high	high	low	gas,ash
Helgafell, Iceland	1973	Shield	moderate	medium	low	high	lava, ash
Mt. St. Helens, WA	1980	Strato	high	high	high	high	gas,ash
Laki, Iceland	1983	Shield	moderate	medium	low	high	lava,ash
Kilauea Iki, HI	1987	Shield	low	low	low	low	lava
Fernandina, Galapagos	1994	Shield	low	low	low	low	lava

Scatter Plot 1 - Silica Content

Eruptive Violence Magma Viscosity

High Medium Low

High

Moderate

H

Low

Scatter Plot 2 - Water Content

Eruptive Violence Magma Viscosity

High Medium Low

High

Moderate

L

Low

Questions:

What is the relationship between the magma viscosity and the eruptive violence?
Example: If magma is viscous, the eruptive violence will be ____. Then give the other example.
Which has the higher water content, a high or low viscosity magma?
What is the relationship of the magma's composition (SiO₂, H₂O) to the types of materials (ash, lava, etc) ejected from the volcano during an eruption? Give more examples than this one.
Example: If the magma's silica and water content are both high, the volcano ejects ___.
How is the magma viscosity related to its silica (SiO₂) and water (H₂O) content ?
What is the relationship between the magma's composition (SiO₂, H₂O) and the specific type of volcano (strato, cinder, etc) produced? Give examples for each type of volcano.
Example: If the magma's silica and water content are both high, the volcano will be a ___.