Claire Chadwick; Lauren Maurizio; Robin Humphreys; and Vijay Vulava
Magma and Volcanoes
In this section, we will explore the properties of magma and how their mineral composition and physical properties may impact their behavior during volcanic eruptions. Magma can have different amounts of silica (SiO4) and dissolved gases (like CO2, SO2, and H2O). These factors affect how magma erupts and the type of volcano it will form when it solidifies. Note that the amount of silica in magma and its viscosity are positively correlated. Magma can contain 1% to 10% dissolved gases, much like a soda contains dissolved CO2.
Exercise 1: Properties of Magma
Let’s examine the physical and chemical properties of magma, which controls the type and impact of volcanic eruptions. Use the resources below and answer the following questions.
- Watch the above video for a quick introduction to volcanoes and magma. As always take notes while you watch the video.
- 4 Igneous Processes and Volcanoes – An Introduction to Geology (opengeology.org)
Watch the video above for
- What is magma and where does it come from?
- What is lava?
- Magma does not rise to the surface to form volcanoes everywhere. Where do most volcanoes form?
Let’s explore how the silica (SiO4) and dissolved gas (like CO2, SO2, and H2O) composition affect the eruption style.
- Define viscosity.
- What is more viscous: Water or Maple syrup?
- Lava with low viscosity will be able to flow a long distance before it cools and hardens into rock, or to cool and harden close to the vent?
- The lava in the above question has low silica or high silica?
- Lava with high viscosity will be able to flow a long distance before it cools and hardens into rock or cool and harden close to the vent?
- The lava in the above question has low silica or high silica?
- Contents from one of the two sealed bottles will erupt when vigorously shaken: Plain water or Soda?
- Compared to magma with lower gas content magma with a higher gas content will erupt: More explosively or Less explosively
- Define an effusive eruption.
- Define an explosive eruption.
- Silica and gas content in effusive eruptions are high or low?
