EES Exam 2 Questions and answers. Latest Update. Verified.

EES Exam 2 Questions and answers. Latest Update. Verified. Is all volcanic activity violent and explosive? - -No What is magma? - -Melted rock material How does magma vary? - -It varies in composition. Some can have more silica than others. Silica content - -Silica makes magma more viscous because silica tetrahedra link together. Gas content - -Different dissolved gases, such as H2O and CO2, can control how a volcano erupts. What is the difference between rhyolitic and basaltic magma? - -Rhyolitic: high silica content, high gas content, and produces violent explosions. Basaltic: low silica and gas content and erupts peacefully. Andesitic lava - -Somewhere in between rhyolitic and basaltic Pahoehoe - -Smooth ropey flows formed by basaltic lava. It forms because magma is very hot and only the surface is solidifying. a'a - -Rough, blocky flows formed by basaltic lava flows. Forms from slightly cooler lava which is solidifying and breaking up into blocks as it flows. Volcanic ash - -Tiny fragments of lava, essentially glass. Bombs - -Pyroclastic products that form as blobs of lave fly through the air Does all volcanic activity form "volcanoes"? - -No What is a shield volcano and where/how do they form? - -Shield volcanoes are large, with gently sloping sides, and are composed of many basaltic lava flows. example: Hawaii What is a composite volcano and where/how do they form? - -Composite volcanoes have more steeply sloping sides and are composed of layer of lava alternating with pyroclastic debris. They build up steep sides because of the deposition of pyroclastic material during their generally explosive eruptions. Examples: Rhyolitic and Andesitic Which type of volcano is larger? - -Shield Volcano What are calderas and how do they form? - -A caldera forms when a volcano collapses after a large eruption How does volcanic activity occur at mid-ocean ridges? - -It is very common, volcanic activity occurs at two divergent plates. How does volcanic activity occur at continent-continent divergent plate boundary? - -Divergent plate boundaries allow lava to escape. How does volcanic activity occur at subduction zones? - -Volcanoes form as the subducted plate partially melts at a subduction zone. The magma rises towards the surface. example: Andes Mountains How does Volcanic activity occur at mantle plumes? - -Mantle plumes cause melting of the overriding plate which also causes volcanic activity. Example: Yellow Stone National Park Can volcanoes occur at continent-continent convergent boundaries? - -No Divergent Plate Boundaries - -Basalt flows at mid-ocean ridges Subduction Zones - -Rhyolitic/andesitic composite volcanoes Mantle Plumes beneath oceanic plates - -Basaltic shield volcanoes Mantle plumes beneath continental plates - -rhyolitic/andesitic composite volcanoes and calderas. What are some ways we can monitor a volcano and predict the likelihood of it erupting? - -The United States Geological Survey (USGS) monitors volcanoes. They monitor earthquakes, gas emissions and ground deformation. How dangerous are volcanoes, really? - -Volcanoes are dangerous: -Lava flows -Ash/lapilli -Pyroclastic flows -Blasts -Landslides -Mudflows -Earthquakes -Tsunami -Poisonous gas What are the four main causes of "death by volcano"? - --Pyroclastic flow -Tsunamis -Lahars (mudflows) -Indirect (famine) How does pyroclastic flow happen? - -Pyroclastic flow happens when pyroclastic material falls back down, then quickly flows down the slopes of the volcano. Why was the pyroclastic flow associated with the 1980 eruption of Mt. St. Helens especially deadly? - -The blast of the volcano came out of the side and the flow was concentrated on one side of the mountain. It affected 230 square miles. What is a lahar? - -A volcanic mudflow made of ash and water. What are some situations that might especially lead to the likelihood of a lahar associated with a volcanic eruption? - -If the volcano is covered in ice and if there are rivers and lakes at the base of the volcano. What happened at Nevado del Ruiz and why? - -There was a small eruption that traveled through the river and the town was located near the river. It happened very quickly. Why is a lahar flow path more predictable than that of pyroclastic flow? - -It follows preexisting