1. Volcanic activity
Pg. 89

2. Magma Temperature beneath the lithosphere causes rock to melt
As pressure increases, the melting point of rock increases
At any pressure, a wet rock will melt at a lower temp

3. Types of magma
Magma formed from the 3 major types of igneous rock- basalt, andesite, and granite
Major types of magma: basaltic, andesitic, and rhyolitic
Hawaiian volcanoes- basaltic
Mt. St. Helens in Washington are andesitic
Dormant volcanoes in Yellowstone are rhyolitic

4. Mt. St. Helens

5. Magma composition
The viscosity of magma is based on silica content more silica, higher viscosity
Basaltic magma
Volcanoes erupt quietly
About 50% silica
Made from rocks in the upper mantle
Oceanic and continental crust
Andesitic magma
found along subduction zones
Made from oceanic crust and sediments
60% silica, eruptions are in the medium range
Rhyolitic magma
Comes from water rich continental crust
Very explosive
70% silica content

6. Basaltic volcano Andesitic volcano Rhyolitic volcano
Andesitic volcano
Rhyolitic volcano

7. Intrusive activity
When magma cools, it forms structures called plutons
Plutons are based on size and shape
Largest plutons batholiths and stocks; form beneath earths surface; coarse rock
Laccoliths mushroom shaped pluton
Sills and dikes smallest pluton

8. Anatomy of a volcano Magma erupts in an opening called a vent
Around the vent is a crater
Calderas can form when a volcano collapses into the magma chamber

9. Types of volcanoes Shield volcano Cinder cone volcanoes
Mountain w/ broad gently sloping sides that forms when basaltic rock is layered
Cinder cone volcanoes
Forms when material is ejected high in to the air and piles up around a vent
Has steep sides
More explosive
Composite volcanoes
Much larger than cinder cone
Dangerous to humans
Lava alternates with volcanic fragments

10. Types
Shield
Cinder cone
Composite

11. Volcanic Material Tephra- rock fragments thrown into the air
Can be dust, ash, lapilli, volcanic blocks, or volcanic bombs
Rapidly moving volcanic material is called pryoclastic flow

12. Volcano occurrences Convergent volcanism Divergent volcanism
At a convergent boundary
Usually form in the sea
Divergent volcanism
Magma forced upward through faults
Causes seafloor spreading

13. Pg. 90
Create a foldable of the 3 different types of volcanoes. Include a diagram of each on your foldable ( look on pgs for diagrams)
Include the types of magma and how explosive it is