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Devil's Tower


Extra Credit: Create your own working volcano models to compare two types of volcanoes (two different models).
Worth 10 points on your next exam!
  • Due before your next exam.

Volcanoes!

View an Eruption (quicktime)
More at Mr. Cohen's Earth Science Site

Check out the Anatomy of a volcano! 

Can we predict a Volcanic Eruptions?

Deadliest and Most Famous Eruptions Since 1500 A.D.

Eruption
Year
Deaths
Major Cause
Nevado del Ruiz 1985 25,000 Mudflows
Mont Pelée 1902 30,000 Pyroclastic flows
Krakatau 1883 36,417 Tsunami
Tambora 1815 92,000 Starvation

Types of Volcanoes depend on types of Magma.

View the "Earth Revealed": Volcanoes provide clues about what is going on inside Earth. Animations illustrate volcanic processes and how plate boundaries are related to volcanism. The program also surveys the various types of eruptions, craters, cones and vents, lava domes, magma, and volcanic rock. The 1980 eruption of Mount St. Helens serves as one example.

Felsic magma: Explosive Volcanoes, high in Silica,
light colored, slow moving, Subduction Boundaries

Mafic magma: Low in Silica, dark colored, faster moving, not as explosive, Divergent Boundaries

Types of Volcanoes:

Stratovolcano

  • Explosive Volcano 
  • Felsic Magma
  • Found at convergent plate boundaries. 
  • Example: Mount St. Helens
  • Also Called Composite Volcanoes

Shield Volcano

Caldera Volcanoes

Path of the Yellowstone hotspot

  • Yellow and orange ovals show volcanic centers where the hotspot produced one or more caldera eruptions- essentially "ancient Yellowstones"- during the time periods indicated. As North America drifted southwest over the hotspot, the volcanism progressed northeast, beginning in northern Nevada and southeast Oregon 16.5 million years ago and reaching Yellowstone National Park 2 million years ago.

Brainpop

Mount Saint Helens (webcam)

  • 1980 Eruption
  • Subduction boundary
  • Felsic Lava
  • Pyroclastic Flows blew down trees up to 25 kilometers away
  • Result of the Juan de Fuca Plate subducting under the North American Plate.

Mount Vesuvius, Italy

Vesuvius

  • 79 A.D. eruption
  • Buried three Roman Cities
  • Most Famous is Pompeii
  • People were sealed in tombs of volcanic ash

Pyroclastic Flow

  • Killed and covered the people of Pompeii. 
  • The flow of hot ash and rock traveled down the slope of the volcano so fast that no one could escape
  • Videos

Krakatoa: A Volcano that blew up an island. NPR

  • Most violent eruption of historic times
  • Erupted August 27th, 1883
  • Sound of the explosion sent shock waves around the world seven times
  • Caused Tsunamis that killed more than 36,000 people
  • Created beautiful red sunsets even two years after the eruption.
  • People in New York City thought buildings were on fire because of the red sunsets.

Volcanoes in the Solar System

Plutons: Magma chambers cooled underground

Igneous Intrusions:

  • Dike: Sheets of igneous rock that cut across rock layers
  • Sill: Sheets of igneous rock that are between rock layers
  • Laccolith: sills pushed up in a dome shape
  • Batholith: Largest of the plutons or magma chambers
  • Volcanic Neck: Plug of hardened magma in an eroded volcano

Volcanic Life!

Rift eruptions

  • Divergent boundaries
  • Mid-Ocean ridges
  • Produce hydrothermal vents (super-heated water)
  • This hydrothermal vent is called a Black Smoker
  • See the Chimneys!

Hydrothermal vents cause deep ocean life.

  • Bacteria feed off this energy from the earth
  • Other animals feed on the bacteria (tube worms)
  • Only food chain on earth that does not get energy from the sun
  • Aliens of the Deep!
  • See Shrimp Eat!

Go to these links to find out more about volcanoes!