Use the following to complete the sentences. You may use several of these terms
ID: 299634 • Letter: U
Question
Use the following to complete the sentences. You may use several of these terms more than once (27pts):
pyroclastics high low escape shield
basaltic subduction composition parasitic
composite pressure silica rhyolitic
Pacific Ring of Fire andesitic gases temperature
The nature of a volcanic eruption is dependent upon the magma’s _____, _____, and the amount of dissolved ______ within the magma. Each of these will influence the viscosity of the magma. Viscosity is a measure of a fluid’s resistance to flow. Lavas that are _____ in viscosity may travel long distances before congealing and crystallizing into igneous rock. Lavas that are _____ in viscosity do not flow readily. Viscosity and _____ content are directly related. However, ____ temperature magmas and lavas have a higher viscosity than those that are ____ in temperature.
Dissolved gases will expand when magma nears Earth surface. If the magma has a high viscosity, the gases cannot readily ______ and the _____ will build – often resulting in very violent, explosive eruptions. Typically, magmas rich in _____ and that have a higher percentage of dissolved______ produce the greatest amount of _______ which are fragments of pulverized rock, lava, and volcanic glass that are often propelled by the explosive release of ____ under pressure. These magmas are classified as _____ when there are intermediate amounts of _____ and dissolved______ and are called ______ when these components are present in the greatest amount.
_____ cone volcanoes with steep, symmetrical slopes are the most violent of the volcanic mountains. These dangerous volcanoes are comprised of alternating layers of _____ such as ash, cinders, and pumice as well as layers of ______ rock produced by lava flows and are produced along _____ zones most of which are located along the _________.
The largest volcanoes on Earth and in the solar system are _____ volcanoes. These massive structures have low, broad slopes comprised primarily of _____ rock produced by very low viscosity lava flows and tend to form islands in intraplate hot spots or at divergent plate boundaries.
Cinder cones (also called tephra cones) are comprised of ______ . These volcanoes have steep, often asymmetrical slopes that can grow rapidly in height in less than a month. Some of these volcanic cones occur in large groups while others may form ______ cones along the flanks of larger volcanoes.
Explanation / Answer
The nature of a volcanic eruption is dependent upon the magma’s composition, temperature, and the amount of dissolved gases within the magma. Each of these will influence the viscosity of the magma. Viscosity is a measure of a fluid’s resistance to flow. Lavas that are low in viscosity may travel long distances before congealing and crystallizing into igneous rock. Lavas that are high in viscosity do not flow readily. Viscosity and silica content are directly related. However, low temperature magmas and lavas have a higher viscosity than those that are high in temperature.
Dissolved gases will expand when magma nears Earth surface. If the magma has a high viscosity, the gases cannot readily escape and the pressure will build – often resulting in very violent, explosive eruptions. Typically, magmas rich in silica and that have a higher percentage of dissolved gases produce the greatest amount of pyroclastics which are fragments of pulverized rock, lava, and volcanic glass that are often propelled by the explosive release of gases under pressure. These magmas are classified as andesitic when there are intermediate amounts of silica and dissolved gases and are called rhyolitic when these components are present in the greatest amount.
Composite cone volcanoes with steep, symmetrical slopes are the most violent of the volcanic mountains. These dangerous volcanoes are comprised of alternating layers of pyroclastics such as ash, cinders, and pumice as well as layers of andesitic rock produced by lava flows and are produced along subduction zones most of which are located along the Pacific Ring of Fire.
The largest volcanoes on Earth and in the solar system are shield volcanoes. These massive structures have low, broad slopes comprised primarily of basaltic rock produced by very low viscosity lava flows and tend to form islands in intraplate hot spots or at divergent plate boundaries.
Cinder cones (also called tephra cones) are comprised of pyroclastics . These volcanoes have steep, often asymmetrical slopes that can grow rapidly in height in less than a month. Some of these volcanic cones occur in large groups while others may form parasitic cones along the flanks of larger volcanoes.
Answers are given in bold and underlined manner.
[Explanations:
Relation between viscosity, composition of magma, temperature of magma, gas content and distance to flow -
Viscosity means resistance to flow. The magma with higher viscosity will go less distance like rhyolitic magma than the magma with lower viscosity, which will go more distance like basaltic magma. The magma with higher silica content, low temperature and higher dissolved gases is considered a magma with high viscosity. For example: rhyolitic magma. The magma with lower silica content, high temperature and lower dissolved gases is considered a magma with lower viscosity. For example: basaltic magma. Andesitic magma is intermediate type, which have intermediate silica content, intermediate temperature between basaltic and rhyolitic magma, intermediate viscosity and gas content.
An explosive eruption will give rise to andesitic-to-rhyolitic magmas which is characterised by having high viscosities and high gas contents. In this case, a high pressure is developed as gases cannot escape. Non-explosive eruptions will be found in basaltic-to-andesitic magmas which have low viscosities and low gas contents. Due to explosive eruption of lava, pyroclastics are produced which is the combination of rock fragments, lavas, ashes etc.
Types of volcanoes:
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