Transcript Volcanoes
Volcanoes What are the 3 major types of volcanoes? • Shield – Gentle sloping sides, slow moving/runny lava • Composite – Tall, steep sides. Very violent eruptions. Thick sticky lava. Layers made of __________, _____, and pyroclastic materials • Cinder Cone – Short, ______ sides. Layers made of ash. – What do you think pyroclastic means? LAVA DOME A type of volcano often formed on or near another active volcano. Magma rises just under the crust and cools. What is volcanism? Any activity that includes the movement of _________ toward or onto the ________ of the earth. Because of high temperature and pressure in the earth- pockets of magma form when surrounding rock ______, as more rock melts, the pocket grows Predict what happens next. Why does the magma come to the surface? The magma is hotter, and less _______ than rock so it rises to the surface through _______ in the rocksmelting more rock. This occurs mostly at plate boundaries Any magma that makes it to the surface is called ______the opening it comes through is called a ______. The build up of material over the vent is a _______. http://www.youtube.com/watch?v=mYekQtFLT2A http://www.youtube.com/watch?v=ZZnvzSpNLAE&feature=related What state do you think has the most volcanoes? Volcanoes at subduction zones What happens here? Draw a picture of what you think happens. Volcanoes at subduction zones O-C plate boundaries: Oceanic is pushed under the continental, melting the plate. Magma rises to the surface _________, the crust buckles _______, trenches form at the boundary. O-O Same as O-C, just under water. Volcanoes here are called island ______volcanoes. Japan and Alaska Why does Oceanic plate subduct more often the cont? What happens at divergent boundaries? What happens at divergent boundaries? As plates move apart magma comes to the surface making mid ocean _________ Most of the eruptions here goes unnoticed, mountains and volcanoes are continuously forming. They can be seen only on land in ___________. Iceland is in part a __________. Where is Iceland? Hot Spots Not all volcanoes are on __________. Sometimes magma can rise to the surface in the _____________ of a plate. These volcanoes seem like they are stationary, however, as the plate moves over the hotspot new volcanoes are formed, and old ones are __________ away. http://www.youtube.com/watch?v=tfXGbzgGJ74&feature=related Types of lava Different types of ____________ make different types of lava. Mafic- oceanic crust- full of ________ and magnesium- dark in color- small __________quiet eruptions Felsic- continental crust- ________rich- light in color- large crystals-violent eruptions Pahoehoe (Pah-Hoy-Hoy)- slow moving- “______” Aa (Ah Ah)- quick cooling- jagged chunks Pillow lava- when lava flows onto the ocean floor through ____________ Write 2 things you learned about volcanoes today.