1. Shield volcano - Low, broad slopes - Basaltic (mafic) magma
2. Composite volcano (Stratovolcano) - Steep, conical shape - Andesitic to rhyolitic (intermediate to felsic) magma
3. Cinder cone - Small, steep-sided cone - Basaltic (mafic) magma
a. The relationship between the amount of gases in magma and the explosiveness of a volcano eruption is direct: higher gas content leads to more explosive eruptions. Dissolved gases expand as magma rises and pressure decreases; if the magma is viscous, gases cannot escape easily, building pressure until a violent explosion occurs.
b. The relationship between the silica content of magma and the explosiveness of a volcano eruption is also direct: higher silica content leads to more explosive eruptions. Silica-rich magma is more viscous, which traps gases and prevents their easy escape, resulting in pressure buildup and explosive eruptions. Magma with low silica content is less viscous, allowing gases to escape more readily, leading to gentler, effusive eruptions.
Parent Tip: Review the logic above to help your child master the concept of types of volcanoes worksheet.
