What are plate tectonics? The theory of plate tectonics is a interesting story of continents drifting from place to place breaking apart, colliding, and grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the earth's crust and upper mantle to be composed of several large, thin, relatively rigid plates that move relative to one another. The plates are all moving in different directions and at different speeds.
Sometimes the plates crash together, pull apart or sideswipe each other. When this happens, it commonly results in earthquakes. Continental Drift: To see this animation again, just refresh this page! This animation shows you what our planet looked like millions of years ago and what it looks like now! Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.
Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris. Rainier and Mount St. Helens are examples of this type of volcano. Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows.
My name is Vera and I would like to tell you a bit more about volcanoes. The name volcano comes from Vulcan, the Roman god of fire! The molten rock and ash solidify as they cool, forming the distinctive volcano shape shown here. As a volcano erupts, it spills lava that flows downslope. Hot ash and gases are thrown into the air. Some volcanoes are covered with snow and ice.
If they erupt, melted snow and ice mixes with mud and volcanic ash and flows down mountain. Volcanic flows are called lahars. Volcanoes are made of unique rocks called extrusive igneous rocks. They are shown on geological maps with bright colours, like this one.
It is marked with an X. The orange colour on the map indicates the rocks and lava from the volcano. Year Published: When volcanoes fall down—Catastrophic collapse and debris avalanches Despite their seeming permanence, volcanoes are prone to catastrophic collapse that can affect vast areas in a matter of minutes.
Siebert, Lee; Reid, Mark E. View Citation. Siebert, L. Geological Survey Fact Sheet , 6 p. Stovall, Wendy K. Stovall, W. Geological Survey Fact Sheet —, 6 p. Year Published: update to the U. Geological Survey national volcanic threat assessment When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location.
Ewert, John W. Ewert, J. Geological Survey national volcanic threat assessment: U. Geological Survey Scientific Investigations Report —, 40 p. Year Published: U. Geological Survey Volcano Hazards Program—Assess, forecast, prepare, engage At least volcanoes in 12 States and 2 territories have erupted in the past 12, years and have the potential to erupt again.
Geological Survey Fact Sheet —, 4 p. Year Published: A sight "fearfully grand": eruptions of Lassen Peak, California, to On May 22, , a large explosive eruption at the summit of Lassen Peak, California, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as miles to the east. Clynne, Michael A. Clynne, M. Year Published: Eruptions of Hawaiian volcanoes - Past, present, and future Viewing an erupting volcano is a memorable experience, one that has inspired fear, superstition, worship, curiosity, and fascination since before the dawn of civilization.
Tilling, Robert I. Year Published: Eruptions in the Cascade Range during the past 4, years Volcanoes have been erupting in the Cascade Range for over , years. Myers, Bobbie; Driedger, Carolyn L. Year Published: Geologic hazards at volcanoes Most volcano hazards are associated with eruptions. Year Published: This dynamic planet: World map of volcanoes, earthquakes, impact craters and plate tectonics Our Earth is a dynamic planet, as clearly illustrated on the main map by its topography, over volcanoes, 44, earthquakes, and impact craters.
Simkin, Tom; Tilling, Robert I. Year Published: Volcanoes! Geological Survey. Year Published: What are volcano hazards? Myers, Bobbie; Brantley, Steven R. Myers, B. Geological Survey Fact Sheet —97, 2 p. Year Published: This dynamic earth: the story of plate tectonics In the early s, the emergence of the theory of plate tectonics started a revolution in the earth sciences.
Kious, W. Jacquelyne; Tilling, Robert I. Filter Total Items: 5. Date published: May 6, Date published: May 17, This EarthWord is straight up steampunk Date published: May 16, Which sounds more dangerous, lava or mud? The answer may surprise you Date published: August 22, In the sky! Date published: February 1, List Grid. May 20, August 8, Tephra, the general term for volcanic rock fragments exploded or carried into April 19, July 30, Video Sections: Volcanoes: Monitoring Volcanoes.
Attribution: Volcano Hazards Program Office. June 5, Attribution: Natural Hazards. March 8, View looking down onto the northeastern vent.
March 6, This fissure began in the early hours of March 6, erupting spatter and producing lava flows. February 24, Listen to hear the answer.
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