chapter 10 volcanoes
DESCRIPTION
Chapter 10 Volcanoes. 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 . - PowerPoint PPT PresentationTRANSCRIPT
Chapter 10Volcanoes
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.
Magma vs. Lava
Magma – molten material inside a volcano
Lava – molten material on earth’s surface
Draw & Label the parts of a Volcano
Where do volcanoes occur?
1. Where plates move APART
AKA: Divergent plate boundaries
2. Where plates move TOGETHER
AKA: Convergent plate boundaries
Where do volcanoes occur?
3. HOT SPOTS areas of earth that melt
rock & force magma upward
Pacific Ring of Firearea around the pacific plate where earthquakes & volcanoes are common
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
Eruptions• Eruptions can either be quiet or explosive.
• Two factors to determine the type of eruption:
1. Amount of water vapor and other gases trapped in the magma.
2. Whether the magma is basaltic or granitic.
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
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
VIDEOS
• Kilauea Eruption
• Mount Saint Helen Eruption
TYPE 1: SHIELD VOLCANO
• Broad volcano• Gently sloping sides• Quiet Eruption
Hawaiian Islands
TYPE 2: CINDER CONE VOLCANO
• Explosive eruptions throw lava into the air• Lava then cools & hardens into TEPHRA
- steep, smooth sides- loosely consolidated
Paricutin, Mexico
TYPE 3: COMPOSITE VOLCANO
• Vary between quiet & explosive eruptions• Lava & tephra is repeated over & over
Mount Saint Helens
Brain Pop
http://www.brainpop.com/science/earthsystem/volcanoes/