Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
volcanism:any activity that includes the movement of magma toward the surface of the Earth volcano: place where magma reaches the surface magma: liquid, molten rock underground lava: magma that reaches the surface •lost gas, gained rock MID-OCEAN RIDGE: occurs where plates are moving apart •lava flows out smoothly and fluidly from cracks SUBDUCTION ZONE: occurs at subduction boundaries •usually explosive and erupted material is mostly lava HOT SPOTS: areas of volcanic activity in the middle of a lithospheric plates Hawaiian Islands are an example two types of lava: •felsic: much silica (Rhyolitic), light-colored, slow moving (viscous), continental crust •mafic: low silica (basaltic), dark-colored, fast moving (least viscous), oceanic crust • Pahoehoe (puhHOEEE-hoeee): thin mafic lava. – usually hardens with wrinkled surface – means “ropey” in Hawaiian Pahoehoe Lava • Aa (AH-ah): sharp block shapes of hardened mafic lava. – caused by rapid cooling on surface of lava – breaks into jagged chunks Aa Lava Aa Lava Pahoehoe Lava Pahoehoe Aa Pillow lava from Hawaii •many magmas contain dissolved gases that are given off •water vapor, carbon dioxide (CO2), sulfur (S) •magmas with more gases have more explosive eruptions tephra:solid fragments ejected from a volcano ash (<2mm) bombs lapilli (<64mm) blocks Sometimes called pyroclastic material lapilli bombs bombs blocks •Vent: opening from which lava flows •Crater: funnel-shaped pit or depression at top of volcano •Caldera:craters whose walls have collapsed •composed of quiet lava flows •form gently sloping, domeshaped mountain •basaltic (mafic) magma largest = Mauna Loa in Hawaii •Made mostly of tephra and other rock particles •Formed from explosive eruptions •Not very high, narrow base, steep sides •Rhyolitic (felsic) magma •built up of alternating layers of rock & lav •explosive eruptions at first with tephra then quiet with lava •forms large, cone-shaped mountains •made of rhyolitic & basaltic magma Mount Fuji