1. Volcanoes: The Eruptions, The Lava, and The Types

2. Volcanoes form around vents that release magma onto the Earth’s surface.
Lava
Magma chamber

3. What causes volcanoes? Where Volcanoes Form
Tectonic Plate Boundaries!!!
There are lots of uncertainties about why volcanoes form, because scientists have to rely on models based on rock samples and other data.
~75% world’s active volcanoes in Ring of Fire

4. What causes volcanoes?

5. What causes volcanoes?
Hot Spots

6. Types of Volcanoes Shield volcano Cinder cone volcano
Composite/Strato volcano

7. Are all Eruptions Equal?
A quiet eruption
An explosive eruption

8. Why are They Different All magma is not equal
One key factor that controls whether or not an eruption is quiet or explosive is the amount of trapped gases and water vapor in the magma
If gases can escape easily, the eruption is quiet. If the gas builds up high pressures, it eventually will cause an explosive eruption.
The more trapped water vapor in the magma, the more explosive the eruptions
The second factor is the amount of silica in the magma

9. Quiet Eruptions
Some eruptions, are quiet, with lava slowly oozing from a vent.
Magma that is relatively low in silica and other fluids is called Basaltic magma and produces quiet eruptions like those on Kilauea (Hawaii)
Trapped gases and water vapor can easily escape sometimes forming lava fountains
Quiet eruptions occur over hot spots (Hawaii) and divergent boundaries (Iceland)

10. Explosive Eruptions
Some eruptions are very violent. Gases from within the earth's interior mix with huge quantities of dust and ash and rise into the air as great, dark, poisonous clouds called a plume.
Andesitic magma has more silica than basaltic so it erupts more violently
Silica-rich (Granitic) or Rhyolite magma produces explosive eruptions like those at Soufriere Hills volcano.
Rhyolite magma is thick and can trap gas and water vapor causing and buildup of pressure

11. Buried in Ash and Mud
This photo was taken 2 years after the eruption, this once great forest was still trying to recover
Car buried in mud 17 miles away from Mt. St. Helens
Escaping the ash on a beautiful afternoon in May
Hot ash covered everything and traveled hundreds of miles

12. Balsaltic Lava 3 types
A'a Pronounced "ah-ah", this is a basaltic lava that doesn't flow very quickly. It looks like a slowly moving mass of hot Jello. Once it hardens, the sharp spiny surface of A'a lava is extremely difficult to walk across. These types of lava erupts at temperatures above to 1100 degrees C.
Pahoehoe Pronounced "pa-ho-ho", this type of lava is much thinner and less viscous than A'a. It can flow down the slopes of a volcano in vast rivers. The surface of the lava hardens into a thin crust that looks very smooth. Pahoehoe lava can also form lava tubes, where the rock hardens around a fast-moving liquid core. When that core flows out of the tube, a long tunnel remains. Pahoehoe erupts at temperatures of 1100 to 1200 C.
Pillow Lava Pillow lava is typically found erupting from underwater volcano vents. As soon as the lava contacts the water, it's cooled down and forms a hardened shell. As more lava issues from the vent, the shell of lava cracks and more "pillows" come out of these cracks.

13. Pahoehoe
Blocky lava Aa
Pillow lava

14. RHYOLITIC LAVA Relatively high viscosity (flows like wet concrete)
Rhyolite can look very different, depending on how it erupts. Explosive eruptions of rhyolite create pumice, which is white and full of bubbles. Quieter eruptions of rhyolite often produce obsidian, which is bubble-free and black.
Some of the United States' largest and most active calderas formed during eruption of rhyolitic magmas (for example, Yellowstone in Wyoming, Long Valley in California and Valles in New Mexico).

15. ANDESITIC LAVA
          
Intermediate viscosity* (does not flow readily)
Andesite magma commonly erupts violently from stratovolcanoes creating a pyroclastic flow
The word andesite is derived from the Andes Mountains, located along the western edge of South America, where andesite rock is common.
Andesite was the main rock type that erupted during the great Krakatau eruption of 1883.
*Viscosity is the resistance to flow (Molasses vs Water)