1 / 11

Volcanoes and Eruptions

Volcanoes and Eruptions. 8SCIENCE . Review. Where do volcanoes form? Plate boundaries How do volcanoes form? Heat and pressure from inside the Earth produces magma and pushes up to the surface What is a hotspot?

debbie
Télécharger la présentation

Volcanoes and Eruptions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Volcanoes and Eruptions 8SCIENCE

  2. Review • Where do volcanoes form? • Plate boundaries • How do volcanoes form? • Heat and pressure from inside the Earth produces magma and pushes up to the surface • What is a hotspot? • Very hot areas in the mantle that produce volcanoes although they are not found on plate boundaries

  3. Types of Volcanoes • Shield • Cinder cone • Composite

  4. Shield volcanoes • Quiet eruption that produces lava and spreads out in flat layers • These layers build to form slightly sloping sides • Ex: Hawaiian islands produces 2 different types of lava: • Pahoehoe(smooth) - A’a (rough and chunky)

  5. Pahoehoe and A’a lava A’a lava Pahoehoe

  6. Cinder cone volcano • Explosive eruptions that throw lava and rocks high into the air • These bits of rock and hardened lava are called tephra • Tephra layers build up to form steep sided volcanoes

  7. Tephra lava Tephra lava erupted from the 1980 Mount St. Helens Eruption in Washington State

  8. Composite volcano • Produces eruptions that are quiet then violent • Cycles of lava and tephra form different layers • Usually found where one plate is forced under another

  9. What causes an eruption to be quiet or violent? • Amount of water vapor and other gases trapped in magma • High gas content = more violent eruption • Gases are trapped in magma and pressure builds up • As magma moves closer to the surface, there is less pressure and the gas can escape • Amount of silica (silicon and oxygen) present in magma • Low in silica = more quiet eruption

  10. Other volcanic structures • Not all magma flows to the surface • Some may rise from the volcano and cools underground to form other rock structures • Erosion of the rock layers make these visible to us today

  11. CALDERAS IN OREGON (US) AND PHILLIPINES DEATH VALLEY, CALIFORNIA SHIPROCK, NEW MEXICO COLOMBIA

More Related