Volcanic eruptions for journal

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:

1. 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.
2. 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.
3. Repeat step 1 for all the eruptions listed in the table.

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Scatter Plot 2 (WATER H₂O) Procedure:

1. 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.
2. Mt. Etna in Sicily has again been plotted for you. An L was plotted because the magma's water content was low.
3. Repeat step 1 for all the eruptions listed in the table.

Questions:

1. What is the relationship between the magma viscosity and the eruptive violence.
   • Example: If magma is viscous, the eruptive violence will be ____.
   • Complete the above example and give the other example.
2. Which has the higher water content, a high or low viscosity magma?
3. 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?
   • Example: If the magma's silica and water content are both high, the volcano ejects ___.
   • Complete the above example and give other examples.
4. How is the magma viscosity related to its silica (SiO₂) and water (H₂O) content?
5. What is the relationship between the magma's composition (SiO₂, H₂O) and the specific type of volcano (strato, cinder, etc) produced?
   • Example: If the magma's silica and water content are both high, the volcano will be a ___.
   • Give examples for each type of volcano.