Science is showing that the potential for an eruption of some of the earth’s biggest and deadliest volcanoes is very real and imminent. In order to understand why volcanoes are deadly, one must know what causes volcanoes to erupt. Deep down in the earth’s crust or mantle there is melting occurring. This heat is coming from the earth’s core and the constantly moving materials within the earth. When parts of the mantle or crust melt, magma is formed.
It allows us to understand how sedimentary rocks, metamorphic rocks, and Igneous Rocks use one another to not only form the Rock Cycle, but also other processes that are important to our planet. The rock cycle beings with hot magma, deep below the earth’s surface. Once the magma dries, crystallization occurs, and results in igneous rocks. Over time weathering occurs to the igneous rocks. Over time weathering takes over the igneous rocks.
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.
If the redeposit particles are bound together by compaction or | |cementation (formation of new secondary minerals in the spaces between the loose particles), sedimentary rocks are formed. In | |regions where the Earth’s interior temperature and pressure are high enough to change the chemical composition and mineralogy of | |buried igneous or sedimentary rocks, without completely melting them, metamorphic rocks are formed. Distinct groups or assemblages | |of minerals are typically associated with the formation of each of the three major rock types—igneous, sedimentary, and metamorphic| |rocks. Plate tectonics play a major role in the processes of mineral and rock formation. In geologic terms, a plate is a large, | |“rigid” slab of solid rock.
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.
One hazard can often trigger others (e.g. Earthquakes can cause landslides and tsunamis). The San Andreas Fault is a conservative plate boundary that runs 1300km along the Californian coastline. The fracture within the crust, causes crustal instability, between the North American and the Pacific plate. As it traverses, due to convection currents, the tectonic plates are dragged along the entire length of the Californian coast.
In which ways does volcanic activity vary in relation to the type of plate margin along which it occurs? (10 Marks) Volcanic activity can occur at constructive or destructive plate margins, but it can also occur at hotspots in which no plate margin is involved. At destructive margins two plates which are moving together can be either both oceanic plates or one continental and the other oceanic. In the case of one continental plate and one oceanic plate, volcanic eruptions are very violent and emit andesitic or rhyolitic lava. These types of lava are very viscous due to its high silica content.
The nature of an event is initially determined by how the cause was stimulated. Volcanic eruptions occur in many different forms determined by the plate margin they are on. The eruptions on Montserrat 1995 show a strong example of the nature of a volcano at a destructive plate margin. The Soufriere Hills volcano had lay dormant for a long period of time. When the eruption did occur it was seen as explosive as it produced large volumes of acidic lava, ash, pyroclastic flows and steam.
Eventually, the friction is overcome and the blocks slip abruptly, releasing pent-up energy with a huge “snap”—an earthquake” (The Plate Tectonic Model – Page 107). Plates diverge at volcanic zones by the ocean basins. These are long huge cracks were lava rises from below and freezes into the Lithosphere (About.com – Geology). In which plates move past each other is call a transform boundary. These are not that common as the converge or diverge plates and the most common one is the San Andreas fault of California [About.com – Geology].