1. A Volcano is a weak spot in the crust where molten (melted)
rock is able
to come
to the
surface.

2. Rock can exist as a liquid between 700° - 2000° Celsius
- Molten rock comes from the Earth’s asthenosphere
- Below the Earth’s surface it is called Magma
- Above the Earth’s surface we call it Lava
Rock can exist as a liquid between
700° ° Celsius

3. There are hundreds of erupting volcanoes on our planet at all times!
Most of these volcanoes are found along plate boundaries.
The border of the Pacific tectonic plate has more volcanic activity than any other spot and because of this, we refer to this area as the
“Ring of Fire” .

4. Volcanic activity at plate boundaries
Review:
Volcanic activity at plate boundaries
Divergent Boundaries – Lava pours out of the ridge and can create whole underwater mountain ranges over time. If there is enough material it can rise above the surface of the ocean.
Convergent Boundaries – (Subduction Zones) Oceanic crust returns to the asthenosphere, melts and rises as lava. This can build an Island arc or coastal mountain ranges.

5. Remember, a volcanic area that is not at a plate boundary can exist because of a Hot Spot – a location where extra hot magma burns through the crust above it.
Yellowstone National Park, Wyoming

6. Volcanic Activity isn’t limited only to Lava……….
Hot Spring – a pool of heated water caused by a nearby underground body of magma
Geyser – a fountain of hot water and steam that erupts from the ground. Caused by the pressure that builds up when trapped water is heated.

7. *The force of an eruption depends on the gas content within the lava
During an eruption, the gases dissolved in magma (SO2, CO2) rush out, carrying the magma with it.
What Makes a volcano “erupt?”
*The force of an eruption depends on the gas content within the lava
1. Magma Chamber (underground pocket of molten rock)
2. Pipe (narrow crack in the crust)
3. Vent (where lava meets the surface)
4. Crater (bowl shape depression on top)
5. Side Vent (pressure and blockage creates other exits)
6. Lava Flow (gravity creates a river of lava)
7. Mountain (constructed out of material from past eruptions)
Mountain (built from the material from previous eruptions) 6 3 4 7 2 5 1