Volcanic Landforms 6th Grade 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=Jav4GLXecQ 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 Types of Volcanoes: Composite, Cinder Cone, and Shield Shield Volcano Shield Volcanoes Shield Volcano Shield Volcano Shield Volcano Shield Volcanoes 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 Cinder Cone Volcanoes Cinder Cone Volcanoes Cinder Cone Volcanoes Cinder Cone Volcanoes Cinder Cone Volcanoes Cinder Cone 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 Composite Volcanoes Composite Volcanoes Composite Volcanoes 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 Composite Volcano Composite Volcano 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 Lava Plateaus Lava Plateaus Lava Plateaus