volcanic landforms 6 th grade. 2 kinds of volcanic eruptions quiet eruptions: – if magma is low in...
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2 Kinds of Volcanic Eruptions
• Quiet Eruptions:– If magma is low in silica– Lava is low in viscosity and flows easily
• Explosive Eruptions:– If magma is high in silica– Lava is high in viscosity and flows slowly– Explosive eruptions breaks lava into fragments that quickly
cool and harden into pieces of different sizes like ash, cinders, bombs in a pyroclastic flow
Pyroclastic Flow: when an explosive eruption hurls out a mixture of hot gases, ash, cinders, and bombs
• Ash: fine, rocky particles as small as a speck of dust
• Cinders: pebble-sized particles
• Bombs: large particles that range from the size of a baseball to the size of a car
Volcanic Ash Cloud
• http://www.youtube.com/watch?v=Jav4-GLXecQ
Volcanic Eruptions create landforms made of lava, ash, and other materials.
4 Types of Landforms: 1) Shield Volcanoes
2) Cinder Cone Volcanoes
3) Composite Volcanoes
4) Lava Plateaus
Characteristics of a Shield Volcano• A short, but wide, broad volcano (can be as much as 4 miles wide!)
• Caused by thin layers of basaltic lava with low viscosity
• Caused by quiet eruptions
• has a caldera (large, cauldron-shaped crater) on top
• Hawaiian Islands are made up of shield volcanoes (including Mt. Kilauea and Mouna Loa –2 of the most active volcanoes in the world!)
• Very little pyroclastic material
Cinder Cone Volcanoes
• A volcano with a steep slope and a large crater
• Lava has a high viscosity
• Ex. Paricutin in Mexico built up a cinder cone 400 meters high
Composite Volcanoes
• Tall volcanoes with small craters
• Alternate between quiet eruptions and explosive eruptions
• Alternate between lavas that contain basalt and lavas that contain rhyolite
• ex. Mount St. Helens in Washington State and Mount Fuji in Japan
Lava Plateaus
• Eruptions of lava that form flat, level areas
• Thin, runny lava flows out of long cracks and then cools and solidifies
• Ex. Columbia Plateau covers parts of the states of Washington, Oregon, and Idaho