Author Question: Kilauea, a volcano in Hawaii, generates fluid, extensive lava flows. Mount St. Helens, a volcano in ... (Read 49 times)

Beheh · **on:** Jul 16, 2018

Kilauea, a volcano in Hawaii, generates fluid, extensive lava flows. Mount St. Helens, a volcano in Washington State, can produce lava flows that are short and thick, but that can also erupt violently and generate large volumes of ash.

What might these differences indicate about each lava's silica content and temperature?
What will be an ideal response?

Question 2

Differentiate the three types of magma based on igneous composition and silica content.

What will be an ideal response?

epscape · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

Answer: The silica content can affect the temperature and the viscosity of the lava. The more silica that is present, the lower the temperature of the lava and therefore the higher the viscosity. Lava from Kilauea is low in silica and has a high temperature, producing thin, runny lava that can flow for long distances. Mount St. Helens has lava with a higher silica content, which results in a lower temperature and a higher viscosity, creating thick, blocky lavas when lava flows are generated.

Answer to Question 2

Answer: Basaltic magmas have a mafic composition and approximately 50 percent silica. Andesitic magmas have an intermediate composition and 60 percent silica. Rhyolitic magmas have a felsic composition and contain more than 70 percent silica.