Volcanoes form when magma from under the Earth's surface escapes through openings called vents. There are over 600 active volcanoes worldwide, with the most active being Kilauea in Hawaii. Magma is less dense than the surrounding rock so it moves upward towards the surface, eventually erupting and causing effects like lava flows, ash in the air, and new land formations, as well as destruction. Volcanoes occur at divergent plate boundaries where plates move apart, convergent boundaries where they move together, and at hot spots where the Earth's crust is thinner.

1. What are volcanoes? How many active volcanoes in the world? Over 600 What is the world’s most active volcano? Vocab words: Vent Magma chamber Crater lava

2. Why does magma move towards the surface? Magma is less dense than surrounding rock.

5. Where does magma form?

6. Volcanic Vent The opening of a volcano where the magma escapes to reach the earth’s surface

7. Craters The steep walled depression around a volcanoes vent

8. How do Volcanoes Form? heat and pressure changes the rock to melt forming liquid magma Magmas less dense than rock, forced slowly towards earth’s surface

9. Effects of Eruptions Floods Lava Flows Ash, rock, chemicals in the air (acid rain) Burning New land masses Destruction Mud Flows

10. Kilauea in Hawaii

11. The Hawaiian name "Kilauea" means "spewing" or "much spreading," in reference to the lava flows

12. Most Recent Eruption Continuous since January 3, 1983 Number of Historical Eruptions 61

14. Effects of Eruptions Ash – harmful to life, buildings, roads High temperatures – can ignite wood

18. Mt Spur, Alaska

20. Montserrat

21. Montserrat 1995 - 2004

24. Pyroclastic flow – hot volcanic gas and ash moving in a cloud directly over the Earth’s surface Acid rain – results when sulfur gases from volcano mix w/ water in the atmosphere Harmful to vegetation and aquatic life

29. Where do volcanoes occur? They often occur when Earth’s tectonic plates: Move apart – divergent boundary Move towards each other – convergent boundary At “Hot Spots” – where crust of Earth is thinner than normal

31. Divergent boundary

32. Iceland Mid-Atlantic Ridge

33. Hekla Hekla is located in Iceland last erupted on February 20, 2000 At a divergent plate boundary composite volcano began erupting in 1819

34. Iceland

35. Iceland

36. Convergent boundary

37. Mt St Helens

38. Soufriere Hills on Montserrat Example of a convergent boundary responsible for volcanism