Volcanoes

1. Volcanoes Chapter 11 Section 11-2

2. Volcano The place where magma reaches the Earth’s surface

3. Vent - The opening from which lava erupts Vent

4. Crater – funnel shaped pit or depression at the top of a volcano cone

5. 4 Major Types of Lava • Type 1 • Dark colored • Contains lots of water • Rich in iron and magnesium • When this lava cools, igneous rocks such as basalt are formed • Type 2 • Light in color • Contains little water • Rich in silicon and aluminum • Compounds of these elements account for the light color • When this lava cools, it forms the igneous rock rhyolite

6. 4 Major Types of Lava • Type 3 • Chemical composition close to the dark colored type and light colored type • Andesite is an example of the igneous rocks formed • Type 4 • Contain large amounts of gases such as steam and carbon dioxide • Forms rocks with many holes as lava cools because gas bubbles are trapped • Examples are Scoria and Pumice

7. During volcanic eruptions, many rock fragments are blown in the air. • VOLCANIC DUST: • very fine • Less than .25 millimeter in diameter • Tiny as grains of flour • VOLCANIC ASH: • Particle size is between .25mm to 5 mm • 5 mm is the size of rice grains • VOLCANIC BOMBS: • Centimeter to a meter in size. • Cinders are volcanic bombs the size of golf balls

8. Types of Volcanoes

9. Cinder Cones • Form from explosive eruptions of rock particles • Low cone, narrow base, steep sides • Paricutin, Mexico • Volcanoes that consist predominantly of pyroclastic materials are called cinder cones. These mountains, such as Capulin Mountain in New Mexico (USA), are easily eroded and usually do not reach great heights. Types of Volcanoes

10. Pyroclastic material is another name for a cloud of ash, lava fragments carried through the air, and vapor. Such a flow is usually *very* hot, and moves *rapidly* due to buoyancy provided by the vapors. Pyroclastic flows can extend miles from the volcano, and devastate life and property within their paths. Damage from pyroclastic flows can occur by impact of rock fragments moving at high speeds or burial of the surface with ash and coarser debris a foot or more thick. Hot pyroclastic surges may start fires and kill or burn people and animals. The most devastating pyroclastic flow occured during the eruption of Mt. Pelee in 1902.

13. Shield volcanoes, on the other hand, are predominantly lava-based landforms that have gradual slopes and wide bases, because they release fluid lava slowly. These volcanoes can create huge landforms. Mauna Loa and Mauna Kea on the island of Hawaii (The Big Island) are classic examples: Mauna Kea has a base on the ocean floor more than 200 kilometres (120 miles) wide. • Shield Volcano • Forms from quiet watery runny lava flow over large area • Gently sloping dome shaped mountains • Example: Mauna, Hawaii

14. Shield Volcano • Forms from quiet watery runny lava flow over large area • Gently sloping dome shaped mountains • Example: Mauna, Hawaii

15. Composite Volcano • Alternating layers of rock particles and runny lava • Violent eruption first then quiet eruption that covers the rock particles • Cone shaped mountains • Mt. Fugi

16. Caldera • Crater, top of a volcano, that collapses or explodes to form a large pit

17. Volcanic Activity • Volcanic activity is unpredictable • In order to indicate reactivity of volcanoes, scientist classify them as either active, dormant, or extinct. • Active volcano • Erupts continually and periodically • An active volcano is a volcano that has had at least one eruption during the past 10,000 years. • Dormant Volcano • A sleeping volcano • Known to have erupted in modern times • A dormant volcano is an active volcano that is not erupting, but supposed to erupt again. • Extinct Volcano • Not known to have erupted in modern times but remain unpredictable • An extinct volcano has not had an eruption for at least 10,000 years and is not expected to erupt again in a comparable time scale of the future.