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Volcanic Hazards Lesson

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Magma Basics

What are Igneous Rocks? "Igneous" is derived from the Latin word for “fire” - ignis. Thus, rocks that are “fire-formed”: molten rock (magma) cools to form a solid rock

What is magma?

Magma is molten rock, and contains:

Melt Solids Volatiles
Liquid, composed of mobile ions Silicate minerals that have already crystallized from the melt gases dissolved in the melt, including water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)

How is magma made?




How does magma get to the surface?

Rocks at great depth Rocks near the surface
  • Magma is less dense than the surrounding (host) rock
  • Host rock warm, deform plastically
  • Magma can easily push aside softened host rock
  • Host rock cold & brittle
  • Magma ascends through fractures or stoping (blocks of wall rock break off and then sink into the magma)