Volcanoes

Zones of Volcanism Volcanism describes anything related to the release of heated fluid from the earth 3 types Convergent volcanism Divergent volcanism Hot spots Flood basalts happen when hot spots occur under continental crust This happens when lava flows out of long cracks called fissures

Volcanoes A volcano is a weak spot in the crust where molten material, or magma, comes to the surface. Volcanic belts form along the boundaries of Earth’s plates.

Ring of Fire – a major volcanic belt that rims the Pacific Ocean.

Volcanoes and Plate Boundaries Volcanoes often form where two oceanic plates collide or where an oceanic plate collides with a continental plate. In both situations, an oceanic plate sinks through a trench.

Rock above the plate melts to form magma, which then erupts to the surface as lava.

Hot Spot Volcanoes A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.

Magma Reaches Earth’s Surface When a volcano erupts, the force of the expanding gases pushes magma up until it flows or explodes out of the vent.

Volcanic Eruptions Within the last 150 years, major volcanic eruptions have greatly affected the land and people around them.

Eruption Cloud Clouds of tephra and gases from an eruptions spreads across the sky for hundreds of miles.

Shield Volcano Largest of the 3 types Long gentle slopes Layers of solid basaltic lava Quiet/gentle eruptions

Cinder Cones Smallest of the 3 types Steep sloped and cone shaped Usually basaltic lava Explosive eruptions Usually at the edges of larger volcanoes

Composite Larger than cinder cones Tall mountains Layered with granitic rock and lava flows Cycles through periods of dormancy and explosive eruptions. Sometimes called a stratovolcano

Landforms From Lava and Ash Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include composite volcanoes, shield volcanoes, cinder cone volcanoes, and lava plateaus.

Lava Plateau A lave plateau is a plateau that is formed by lava during a volcanic eruption.

Caldera A caldera forms when an volcano’s magma chamber empties and the roof of the chamber collapses. The result is a large, bowl-shaped caldera.

Landforms From Magma Features formed by magma include volcanic necks, dikes, and sills, as well as batholiths and dome mountains.

Volcanic Neck A volcanic neck is a cylindrical-shaped landform standing above the surface created by magma solidifying in the vent of a volcano. This is Devil’s Tower in Wyoming.

Dikes A volcanic dike is a rock structure that cuts across existing volcanic layers

Sills A volcanic sill is a sheet of magma which is parallel to the surrounding rock. Sills store magma compared to dikes which transport magma.

Batholiths A batholith is a mass of rock formed when a large body of magma cools inside the crust. Several large batholiths form the core of mountain ranges in western North America. Half Dome in Yosemite National Park, California, is part of the Sierra Nevada batholith.

Volcanoes in the U.S. Active volcanoes in the U.S. are found mainly in Hawaii, Alaska, California, Oregon and Washington.

Forecasting Volcanic Eruptions Volcanoes are difficult to forecast because they can cause so many different disasters themselves. The volcanic gases that come with a volcanic explosion mixes with the ash and clouds formed by the eruption and acid rain may fall in your area.  Volcano eruptions throw objects and debris during strong eruptions. Poisonous gases, lava, and ash are all major events during volcanic eruptions.  

Famous U.S. Volcanoes Mount St. Helens in Washington – last erupted in 1980 killing 57 people Mauna Loa in Hawaii – the largest volcano on our planet and also one of the most active volcanoes on our planet. It erupts quite often is and is constantly monitored for its next eruption

Resources http://library.thinkquest.org/CR0212082/ndvol.htm http://www.fema.gov/kids/volcano.htm http://belmont.sd62.bc.ca/teacher/geology12/photos/volcanoes/features.htm Prentice Hall, Inc.