1. Volcanoes
Geography 12
Ms. Inden

2. Volcanology; volcanologist
The study of the ways solid, liquid or gaseous materials are forced into the earth's crust or ejected onto the surface; a person who does this studying

3. A few terms Molten – melted
Magma – molten rock when it is still underground
Lava – magma that has reached the surface

4. Where does magma come from?
Radioactive decay or uranium and thorium
Friction created by the movement of plates
The magma develops in a magma chamber below the earth

5. Ka-boom!
The rock expands as the temperature rises, and also gas is produced
This causes pressure underground
The magma will erupt (now lava), along with gasses, steam, ash, volcanic bombs and rock fragments
The eruption, and the violence involved depends on the sort of volcano the type of rock involved (more on this later)

6. Animation of a strata volcano

7. Extrusive
Intrusive
When lava or other materials reach the surface they are called extrusive
Form extrusive igneous rock when cooled
When magma is injected into the crust (never reaching the surface), it is called intrusive
Form intrusive igneous rock when cooled
Sometimes exposed through erosion

8. You need to know batholith, laccolith, sill and dike
Which landforms on this image are intrusive, and which are extrusive?
What would cause a batholith to be exposed?

9. Intrusive landforms Most magma is intruded
Intrusive igneous rock has bigger crystals than lava which is cooled quickly at the surface
Batholith – at least 100 km, magma cools slowly
Sill – horizontal intrusion
Dikes – cuts through bedding planes vertically
Laccolith – smaller than batholith - fills up a chamber or cavern

10. This volcanic flow probably ran into a glacier, or possibly a cliff – this part of the lava cooled quicker, creating these columns
Look for columns like this on the highway toward Vancouver – south of Quesnel

12. Giant’s Causeway in Northern Ireland