Volcanoes & Volcanic Eruptions

What is a Volcano? A volcano is an opening where magma comes to the Earth’s surface. Magma at the Earth’s surface is called lava. Lava Vent Magma chamber

Example: honey has a higher viscosity than water Volcanic Eruptions Not all volcanoes are explosive. The type of eruption depends on the composition of the volcano’s magma, its viscosity and the amount of dissolved gases. Viscosity is the resistance to flow. High viscosity = thicker magma, flows more slowly Low viscosity = thinner magma, flows quickly Example: honey has a higher viscosity than water

Magma Composition - Explosive Magma that has high silica content has a higher VISCOSITY and lots of dissolved gases. This type of magma leads to EXPLOSIVE volcanic eruptions.

Magma Composition – Non-explosive Magma that has LOW silica content has a lower VISCOSITY and less dissolved gases. This type of magma is thinner and flows more easily causing NON-EXPLOSIVE eruptions.

Non Explosive Eruptions Quiet eruptions rivers of red hot lava flow across the surface slowly Lava is extruded Example: Hawaii

Non-explosive Eruptions Lava flows slowly out of the volcano’s vent traveling down the sides of the volcano. Hawaii

Explosive Eruptions Debris and gases shoot out at high speeds No lava flow Molten material is blown into pieces, some stay in the atmosphere for years! Pyroclastic material is forced out Example: Mount Saint Helens in Washington

Explosive Eruptions Lava erupts out of the volcano’s vent sending gases and pyroclastic material into the air. Mount Saint Helens in Washington

Keep these notes in your binder – we will go over them tomorrow Keep these notes in your binder – we will go over them tomorrow. We will also go over this week’s quiz review 

How the Universe Works: Volcanoes Start Discovery Education Video “How the Universe Works: Volcanoes” username: uticascience password: discovery

Brain Pop http://www.brainpop.com/science/earthsystem/volcanoes/