PPT-Volcanoes UNIT - 8 WHAT IS A MAGMA

Magma is a mixture of molten rock volatiles and solids that is found beneath the surface of the Earth In some instances it solidifies within the crust to form plutonic rocks In others it erupts onto the Earths surface to form . Lava Video. Volcanoes, magma, and lava. Volcanoes are weak spots in the crusts where molten material, or magma, comes to the surface.. When magma reaches the surface it is called lava.. The lava released during volcanic activity builds up Earth’s surface, it is a constructive force.. Chapter 5. Rigid Earth to Plate Tectonics. Learning Objectives. Know the different types of volcanoes and their associated features. Understand the relationship of the volcanoes to plate tectonics. Know what geographic regions are at risk from volcanoes. Yellowstone Park is not only spectacular but also unique. It is the result of three volcanic eruptions, the likes of which have never been seen in all of recorded history. The first eruption occurred 2 million years, followed by two more eruptions 1 million years and 600,000 years ago. Below Yellowstone Park there is a hot spot that is generating basaltic magma. At the time of each of their three eruptions, the magma chamber began to produce large volumes of basaltic magma. Because of its low viscosity, the basaltic magma quickly rose to the bottom of the granitic continental crust. However, because the density of basaltic magma (density about 3) is slightly higher than that of granite (density about 2.9) it could not force its way through the granite to the surface. Instead, it began to pool beneath the granitic crust. The amount of heat trapped within the molten basaltic magma was enough to melt the minerals making up the overlaying and surrounding granite, forming a growing mass of granitic magma. Granitic magma is highly viscous and extremely gas-charged. Although it rose only very slowly, the granitic magma advanced upwards by melting even more of its own overlying granitic rock. At some point, radial fractures began to form around the rising mass of granitic magma. These fractures allowed steam eruptions to vent gas. Shortly after, with the overlying granitic rock severely weakened by the fractures, the highly gas-charged granitic magma erupted. The land to a distance of 200 miles in all directions was decimated. Pyroclastic flows, the most destructive eruptive features known, swept across the countryside. Ash fell across the country from the eruption site to the Atlantic Ocean. Ash polluted the world’s atmosphere, blocked the energy of the Sun, and plunged the Northern Hemisphere into a frozen wasteland for years. Can such an eruption occur in the Yellowstone region again? All the evidence suggests that the magma chamber below Yellowstone Park is current rising. According to the director of the Yellowstone Volcanic Observatory, it is not a question of whether or not another super-eruption CAN happen; it’s a question of WHEN it will happen!. Lava begins as . . , which usually forms in the asthenosphere. The materials of the asthenosphere are under great pressure. Liquid magma is . . dense than the solid material around it. Therefore, magma flows upward into any cracks in the rock above. As magma rises, it sometimes becomes trapped beneath layers of rock. But if an opening in weak rock allows the magma to reach the surface an . The Nature of Volcanic Eruptions. Volcanoes give the opportunity to look at what happens deep beneath the Earth’s surface. . On May 18, 1980 Mount St. Helens erupted and change the surrounding area in Yakima, Washington. It released a lot of ash and debris into the air and surrounding area. . Volcanism is mostly focused at plate margins. Pacific Ring of Fire. This map shows the margins of the Pacific tectonic plate and surrounding region. The red dots show the location of active volcanism. Notice how the majority of the volcanism is focused in lines along the plate boundaries? For this region is the area known as the “Pacific Ring of Fire”.. Earth Science Fall . 2012 . Vocabulary: . aa. – jagged chunks of lava formed by rapid cooling on the surface of the lava flow . Vocabulary:. Caldera- large basin-shaped depression formed when an explosion destroys the upper part of a volcanic cone or when the magma chamber below a volcano is emptied during an eruption. By Robbie Barker, Maximilian Bryson, and Brendan . P. etrili. What is a volcano. A volcano is an opening in the Earth’s surface through which magma rises.. Formation of volcanoes. 1.Most volcanoes occur at colliding boundaries.. What You Will Learn. Describe the formation and movement of magma. . Explain the relationship between volcanoes and plate tectonics. . Summarize the methods scientists use to predict volcanic eruptions. . Volcanism is mostly focused at plate margins. Pacific Ring of Fire. This map shows the margins of the Pacific tectonic plate and surrounding region. The red dots show the location of active volcanism. Notice how the majority of the volcanism is focused in lines along the plate boundaries? For this region is the area known as the “Pacific Ring of Fire”.. 8. th. . Grade Science. Earth. ’. s crust is made up of huge slabs called . plates. , which fit together like a jigsaw puzzle. These plates sometimes move.. Between the Earth. ’. s crust and the . 9.1 – How & Where do Volcanoes Form?. One of the most dramatic activities associated with plate tectonics is the eruption of a volcano.. Volcano refers to both:. The . opening. in Earth’s crust through which molten rock, gases, and ash erupt.. What You Will Learn. Describe the formation and movement of magma. . Explain the relationship between volcanoes and plate tectonics. . Summarize the methods scientists use to predict volcanic eruptions. . . . Cause. most volcanoes are formed when two of Earth’s plate collide. the collision drives one of the plates under another . the plate that is under the other one begins to melt-->this melted rock is known as magma.