1. Unit 5 Volcanoes

2. I. Volcano Basics a.A volcano is a mountain that forms in the Earth’s Crust when molten material (magma) reaches the surface b. Volcanic belts form along the boundaries of the tectonic c. The Ring of Fire is a major belt of volcanoes in the Pacific Ocean

3. II. Volcanoes and Boundaries a.Volcanoes at divergent boundaries are found at the mid-ocean ridge b. Volcanoes at convergent boundaries occur at the subduction zones i. The rock goes under the continental crust and melts back into magma ii. This magma then is rising to the surface because it is less dense and forms a volcano iii. This can sometimes cause an island arc when the subduction zone happens in the middle of the ocean

4. III. Hot Spots a.Magma erupts through the crust and reaches the surface b. This does not happen at a plate boundary c. Hot spots stay at one place for millions of years

5. IV. Volcanic Eruptions a.Inside the Volcano i.Magma Chamber: this is where the magma is kept until it is forced up through the volcano ii.Pipe: magma moves through this from the earth’s crust and up through the top of the volcano iii.Vent: The opening at the top of the volcano iv.Lava Flow: the lava that pours out the vent v.Crater: bowl-shape that may form at the top of the volcano around the vent

6. IV. Volcanic Eruptions b. An eruption is when expanding gases push magma from the magma chamber through the pipe and out through the vent c. Two Types of Eruptions i. Quiet eruption ii. Explosive eruption d. Quiet Eruptions i. Has low-silica magma ii. The magma is thin and runny iii. The magma can flow for kilometers iv. This magma oozes out of the vent v. Most Hawaiian Islands are formed from these eruptions

7. IV. Volcanic Eruptions e. Explosive Eruptions i. Has high-silica magma ii. Magma is thick and sticky iii. Magma clogs the pipe and as the gases build up it causes pressure iv. Eventually, this pressure explodes through the vent of the volcano with incredible force v. Lava is thrown from the vent vi. This lava quickly cools when in the air and turns to small rocks called volcanic ash vii. Lava can sometimes from large pieces called bombs

8. V. Volcanic Hazards a.Pyroclastic Flow: a mixture of hot gases, ash, cinders, and bombs that flow from the volcano during an explosive eruption b.List reasons why this would be dangerous 1. ___________________________________________________ 2. ___________________________________________________ 3. ___________________________________________________

9. VI.Stages of Volcanic Activity a.Active: continuing to erupt and shows signs of future eruptions b.Dormant: expected to erupt again but has not erupted for a while c.Extinct: unlikely to erupt ever again (hot spot volcanoes)

10. VII. Volcanic Landforms from Lava a.Cinder Cone: When the volcano is built up by thick, sticky magma (holding a lot of silica) creating a cone shaped hill

12. VII. Volcanic Landforms from Lava b. Composite Volcanoes: this is a cone shaped mountain that was created by magma and lava with different levels of silica

14. VII. Volcanic Landforms from Lava c. Shield Volcanoes: a wide, sloping mountain due to the low silica lava that is always flowing out of the vent

16. VII. Volcanic Landforms from Lava d. Lava Plateaus: the thin, runny lava flows out of cracks in the crust and flows long distances before hardening creating a high, level platform called a plateau.

18. VIII. Volcanic Landforms from Magma a. Volcanic Neck: forms when magma hardens in the pipe and the rest of the surrounding rock wears away

20. VIII. Volcanic Landforms from Magma b. Dome Mountains: Hardened magma is forced up to the surface. Causes the rock to bend

22. VIII. Volcanic Landforms from Magma c. Batholith: A large body of magma cools inside the crust. This can form the core of many mountain ranges