Analyse the factors that cause differences in the hazards posed by volcanoes around the world (40 marks) June 2013 Volcanoes are forms of major extrusive activity and are openings in the Earth’s crust where molten rock and gases reach the surface. The eruption of volcanoes throws out lava, rocks, ash and gases in various proportions. How hazardous a volcano is, depends on a variety of human and physical factors that work in conjunction to determine the level of damage a volcano can have on the human population. The location of a volcano is a large variable which determines the nature of its eruption. Volcanoes are found mainly in three locations, at constructive and destructive plate margins and at hotspots.
The area is subjected to frequent earth movements and has a long history of volcanic activity. The mountains have formed as a result of seismic activity. The American coast is part of the North American Plate; the Pacific Ocean to the west lies on the Juan de Fuca plate. The Juan de Fuca plate is subducted below the North American plate. As the subducted Juan de Fuca plate is subjected to increasing pressure it becomes hotter and begins to melt.
These types of lava are very viscous due to its high silica content. This is because the lava rises from the subduction zone through continental lithosphere which has a low density and is filled with air spaces containing gases which become incorporated into the lava. This very viscous lava often blocks off vents of volcanoes and when the pressure building up in the vent is eventually released, the top of the volcano can be blown off leaving a huge crater, such as in the 2002 eruption of Mount Etna in Sicily. When the two plates involved are oceanic, explosions tend to be less violent than this as the melted lithosphere which forms the lava is denser and so contains fewer gases. At constructive boundaries where plates are moving apart from one another, basaltic lava is erupted between the gaps.
Before the eruption of May, 1980, the elevation at the top of Mount St. Helens was about 3 km. Mount St. Helens is a composite volcano (or stratovolcano), a term for steep sided, often symmetrical cones constructed of alternating layers of lava flows, ash, and other volcanic debris. Composite volcanoes tend to erupt explosively and pose considerable danger to nearby life and property. Mount St. Helens last eruption was from October 2004 to
A volcano is a surface landform resulting from the extrusion of magma from underground as lava, ash, rocks, and gasses are erupted in various proportions. A hazard is something that poses a threat to life, the environment or property. Volcanoes can compromise all these things through the many hazards volcanoes presents. These include lahars, flash flooding, landslides, pyroclastic flows, ash clouds and many others. Each year, around 60 major volcanoes erupt globally.
NOVA: Volcanoes Volcanoes are landforms where molten rock erupts through the surface of the planet. Think of them as pimples on the face of the earth. Today, there are over 1,500 active volcanoes on earth’s surface. Volcanoes cause serious hazards to not only people, but the environment and the nature around us as well. If an eruption were to occur, a number of life-changing things would happen.
4. Define silicate and name one. Most igneous rocks are composed of mainly silicate materials, Quartz is a light silicate. 5. What is at the difference between light and dark silicate minerals?
8. How does hornfels form? Rock contacts with magma and bakes rock. 9. Know that the type of metamorphic rock relates to how much heat and pressure the rock was exposed to.
Associate Level Material History of Rock Worksheet Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of igneous rocks. |Two cycles determine how mineral deposits are formed the rock cycle and the tectonic cycle. Heat from the Earth’s interior melts | |some of the rocks in the crust; the upper part of the lithosphere. Molten rocks lower in density than the surrounding cooler | |material rise toward the Earth’s surface and eventually cool and harden near to or on the surface. The composition, temperature, | |pressure, and cooling process of the molten material determine the minerals and rock types formed.
In the earth's atmosphere, neon only comprises 0.0018 percent of the volume. On the earth, neon is always present as a gas. There are many physical properties of neon, such as the fact that it is colorless, odorless, and tasteless. Also, neon is lighter than air. With a density of density 0.89990 g/liter.