Field report on observations taken

Field report on observations taken - Field report on the...

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(Figure shows the location of the Valles Caldera) yer (tan very top 1.3 million yrs old) and the pumice layer (white middle layer 1.6 million yrs old). showing a straight line. The contact point with layer two (pumice) and layer three (ignimbrite) joins at a slanted angle towards the bottom ure 5 shows the geothermal pool coming from the mountain side) Field report on the observations of outcrops along the Valles Caldera. The Valles Caldera located at N 31° 51’ 1” W 106° 27’ 35” within the Jemez Mountains of Northwestern New Mexico. The caldera sits upon the largest active rift in North America along with the most active volcanic range in New Mexico. The Valles Caldera was believed to have been formed around 1.6 million years ago when a massive explosion (300 km) erupted into the atmosphere and sent the debris across the landscape. Due to the immense amount of material projected into the air and spread across the landscape a large crater was left in the earth’s crust that was surrounded by extremely steep cliffs. These cliffs and surrounded landscape soon fell into the caldera and filled it up. This type of volcano is observed almost like a hole after the initial explosion being the letter “V” and being filled in almost like a bowl like structure or a much less stepper “U”. The Valles Caldera itself stretches roughly 22 kilometers or 10 miles in diameter. The reason for such a large eruption radius associated with a caldera as opposed to other volcano (i.e. lava domes) is due to the process in which the magma makes an attempt to surface. With a lava dome the magma find its way easily through a vent with little trouble which gives the “spewing” effect and a relatively small eruption radius. However, with a caldera as the magma approaches the surface from a hot spot and is unable to surface due thickness of crust or composition of it. This becomes a recipe for high pressure to build up beneath the surface due to the heat and overall volume of the magma wanting to surface. The pressure soon turns to a ticking time bomb as the overall surface of begins to rise generally around a large area of land which takes the shape of a
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dome. When the crust finally gives the explosion can be of nothing man has ever witnessed. In the case with the Valles Caldera over 300 km of material was projected into the atmosphere in three different forms. One of the being completely air borne until it lands in a somewhat cooled state known as pumice; while another comes crashing down in a fiery gaseous liquid. As for the third, it stays land borne throughout its journey. These three forms are the main pieces of evidence that can all be collected and observed being scattered around the caldera as far as other states and in some cases other countries. In the case that debris from an explosion is found on another continent, experts can conclude the theory of plate tectonics; however, no evidence will be gathered at the Valles Caldera with the only outcrops being ones immediately surrounding the caldera. With those points implied, the
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This note was uploaded on 07/17/2011 for the course GEOL 4201 taught by Professor Staff during the Fall '10 term at Texas Tech.

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Field report on observations taken - Field report on the...

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