A volcano is a mountain that forms when molten rock is forced to the Earth’s surface. Volcanoes can by active, dorma

1. Volcanoes A volcano is a mountain that forms when molten rock is forced to the Earth’s surface. Volcanoes can by active, dormant, or extinct.

2. Active Volcano… Kilauea Volcano is presently one of the most active volcanoes on Earth.

3. Dormant “Sleeping” Volcano Mt. Hood, Oregon Dormant Volcano: A volcano which is presently inactive but which may erupt again. Most of the major Cascade volcanoes are believed to be dormant rather than extinct.

4. Extinct Volcano Kohala Volcano Extinct Volcano: A volcano that is not presently erupting and is not likely to do so for a very long time in the future.

5. Where do volcanoes form?

6. Volcanoes form when hot material from below rises and leaks into the crust. • Eventually, but not always, the magma erupts onto the surface. Strong earthquakes accompany rising magma.

7. Parícutin, Mexico, 1943 • In the winter of 1943, the countryside near Parícutin, Mexico was rocked by a series of earthquakes. The tremors lasted for nearly two weeks when a fissure open in a farmer's field and the birth of cinder cone was underway. Within 12 hours of the initial eruption, the fissure was ejecting pyroclastic material as well as huge clouds of gas and ash. Lava began to spill from the base of the cone building the volcano laterally.

8. Parícutin, Mexico, 1943 • Within 24 hours a 40 meter high cone hurling volcanic bombs several kilometers away had been built. • After nine years of activity, two villages had been buried

11. Anatomy of a Volcano… Crater- A bowl-shaped depression at the mouth of a volcano Magma chamber -A large underground pool of molten rock lying under the surface of the earth's crust Vent- The opening through which the molten rock flows onto the surface.

12. What is the difference between magma and lava?? Lava – molten rock on the earth’s surface. Magma – molten rock deep inside the earth.

13. II. What erupts from a volcano? • Gases: Water Vapor, Carbon Dioxide, Sulfur Dioxide, Nitrogen, Hydrogen, Argon • Rock Fragments: Dust, ash, bombs, and blocks • LAVA!!

14. IV. Types of Lava and Rock Fragments aa – Sharp, jagged lava Pahoehoe - Smooth, wrinkled lava

15. Pillow Lava… Pillow lava – forms on the ocean floor and cools into rounded blobs.

16. In Greek: Pyro – “fire” Clastic – “Broken” Mt. St. Helens Mt. Pinatubo Pyroclastic material - avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the side of a volcano

17. Rock Fragments Lapilli – less than 64 mm in diameter Volcanic ash – 2 mm in diameter Volcanic dust - < 0.25 mm in diameter

18. Volcanic blocks – greater than 64 cm in diameter Volcanic bombs – greater then 64 mm in diameter

19. III. Types of Volcanoes • Shield Volcanoes • Nonexplosive • Thin, runny lava • Gently sloping • Dome-shaped mountains

20. Stratovolcano or Composite • Alternating layers of rock particles and thick lava. • Violent eruptions • Large cone-shaped mountain • Most common type.

21. Cinder Cone • Different sizes of volcanic material • Explosive eruptions • Large bowl-shaped craters • Steep sides with loose rock particles

22. Mafic Lava Felsic Lava

23. What type of volcano am I? Stromboli Volcano in Italy

25. Mt. St. Helens, WA

27. Kanaga Volcano in Alaska

28. Sunset Crater, Arizona

29. Mauna Loa Volcano, Hawaii

30. Water (steam) 77.0% • Carbon dioxide 11.7% • Nitrogen 3.0% • Carbon monoxide 0.5% • Hydrogen 0.5% • Sulfur dioxide 6.5% • Sulfur 0.3% • Chlorine 0.05% • Argon 0.05%