1. Volcanoes

2. A volcano is an opening where molten rock reaches the Earth’s surface. The rock may come form the crust or from the mantle. Volcanoes release internal pressure under the crust.

3. Types of Volcanoes 1. shield volcano: this is a short dome shaped volcano. It usually produces mafic lava, which is dark, hot, thin, and erupts gradually. Shield volcanoes are usually in the ocean (Hawaii).

4. 2. Cinder cone volcano: a cinder cone is tall and cone shaped. It produces felsic lava, which is cool, thick, and erupts violently. –Cinder cones also erupt solid material called tephra. Cinder cones are usually on continents

5. 3. Combination- Combination volcanoes contain both felsic and mafic lava. –They are found throughout the world

6. Types of Lava 1. Pillow lava: this forms when a volcano erupts under water. It cools instantly, forming pillow shaped rocks.

7. 2. Pahoehoe: long ropy strands of rock. Forms when hot (mafic) runny lava cools.

8. 3. Aa (ah-ah): lumpy jagged rocks. Forms when thick (felsic) lava cools. Types of tephra: 1.Volcanic ash (less than 2mm) 2.Volcanic dust (2-10mm) 3.Volcanic lapilli (10-100mm) 4.Volcanic bombs (largest). Bombs are molten when they erupt, and harden on the way to the ground.

9. Plutons Plutons: when magma cools under the surface, it forms masses called intrusions, or plutons. Batholiths: large (over 1000km) plutons Sills: horizontal plutons Dikes: vertical plutons Laccoliths: dome shaped

10. Plutons usually push up on the crust and create hills or mounds. Some batholiths form the base of mountains.

11. Caldera Caldera: when a volcano erupts with incredible force, the sides are weakened. In some cases, the volcano caves in after an eruption. This forms a caldera (cauldron). The caldera fills with rain water and can create a lake (Crater Lake in Oregon)