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Volcanoes
Question | Answer |
---|---|
Hot Spot | An unusually hot region of Earth’s mantle where high-temperature plumes of mantle material rise toward the surface. Hawaiian islands. |
Hawaii | The oldest island, Kauai is no longer active because the island no longer sits above the hot spot. Kilauea, the world’s most active volcano is currently located over the hot spot. Plate is moving Northwest. |
Volcano | An opening in the Earth's crust through which molten magma and gases erupt. Heat and pressure cause rocks to melt and form magma. Mostly associated with subduction, rifting, or seafloor spreading. |
Magma | Molten rock that is under Earth’s crust. Is forced to the Earth surface when a volcano forms. |
Pyroclastic flows | Clouds of tephra that travel down the flanks of volcanoes. They move at high speeds, are very hot, and contain poisonous gases. |
Tephra | Rock fragments and other particles ejected from a volcano. |
Viscosity | A substance’s internal resistance to flow. The more viscous something is, the slower it flows. The less viscous something is, the faster it flows. |
Types of Volcanoes | Classified by the eruption type, magma type and volcanic cone shape. |
Shield | Form from hot, thin, runny lava flows that is erupted from the volcano (low viscosity – low resistance to flow). Usually form at hot spots, from non-explosive eruptions. Are low, very broad, and gently sloping. Biggest type of volcanoes. Ex: Hawaii |
Cinder Cone | Form from explosions of red, hot magma cinders and ash that settle around the main vent and build a steep sided cone. Smallest type of volcanoes – most common. Magma in the vent solidifies – never erupts again. Short lived. |
Composite cones (Stratovolcano) | Formed from a combination of eruptions (explosive (tephra) and non-explosive (lava)). Most violent. Examples: Mount St. Helens, Mount Fuji and Mount Rainer, Mount Vesuvius |
Fissure | A volcanic eruption from a fracture (divergent) in the earth’s surface rather than a volcanic vent. |
Crater | Bowl-shaped depression at top of cone. |
Caldera | Large craters that forms when the top of the volcano collapses into magma chamber, creating a deeper depression, sometimes forming a crater lake. |
Lahar | A flow of volcanic ash and water. |