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Chapter 10 Volcanoes.

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Presentation on theme: "Chapter 10 Volcanoes."— Presentation transcript:

1 Chapter 10 Volcanoes

2 What is A Volcano? A VOLCANO is an opening in Earth’s surface that often forms a mountain when layers of lava & ash erupt After many thousands or even millions of years, magma reaches earth’s surface and flows out through an opening called a VENT. The steep walled depression around a volcano’s vent is the CRATER.

3 Magma vs. Lava Magma – molten material inside a volcano
Lava – molten material on earth’s surface

4 Draw & Label the parts of a Volcano

5 Where do volcanoes occur?
Where plates move APART AKA: Divergent plate boundaries Where plates move TOGETHER AKA: Convergent plate boundaries

6 Where do volcanoes occur?
3. HOT SPOTS areas of earth that melt rock & force magma upward

7 Pacific Ring of Fire area around the pacific plate where earthquakes & volcanoes are common

8 Active vs. Dormant Most of Earth’s volcanoes are DORMANT, which means they are not currently active There are more than 600 active volcanoes in the world The most active volcano in the world is Kilauea in Hawaii

9 VIDEO how volcanoes form

10 Eruptions Eruptions can either be quiet or explosive.
Two factors to determine the type of eruption: Amount of water vapor and other gases trapped in the magma. Whether the magma is basaltic or granitic.

11 Trapped Gases Gases like water vapor and carbon dioxide are trapped in magma by the pressure of the surrounding magma. As magma nears the surface, pressure is reduced. Gas escapes easily = quiet eruption Gas trapped under high pressure = explosive eruption

12 Magma Composition Basaltic Magma – contains less silica, very fluid, and produces quiet, nonexplosive eruptions. Example: Kilauea, Hawaii Granitic Magma – contains a lot of silica, very thick, and high water content. Gets trapped in vents causing pressure to build up resulting in explosive violent eruptions. Example: Mount Saint Helens

13 VIDEOS Kilauea Eruption Mount Saint Helen Eruption

14 TYPE 1: SHIELD VOLCANO Broad volcano Gently sloping sides
Hawaiian Islands Broad volcano Gently sloping sides Quiet Eruption

Paricutin, Mexico - steep, smooth sides - loosely consolidated Explosive eruptions throw lava into the air Lava then cools & hardens into TEPHRA

Mount Saint Helens Vary between quiet & explosive eruptions Lava & tephra is repeated over & over

17 Brain Pop

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