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.
It is the viscosity of magma that largely determines the nature and power of an eruption and the resultant severity of the hazard. Basic magma has a high proportion of dissolved gases and low silica content, making it very fluid. On the other hand, acidic magma is very rich in silica and has a relatively lower temperature, making it very thick and slow moving. The more viscous the magma, the greater the potential for explosive eruptions and these represent the greatest potential hazards. Non-explosive eruptions tend to produce mostly lava flows, which do not represent a particularly serious hazard to people, however they will destroy farmland and buildings.
Ancient Atomic Warfare When the first atomic bomb exploded in New Mexico, the desert sand turned to fused green glass. This fact, according to the magazine Free World, has given certain archaeologists a turn. They have been digging in the ancient Euphrates Valley and have uncovered a layer of agrarian culture 8,000 years old, and a layer of herdsman culture much older, and a still older caveman culture. Recently, they reached another layer of fused green glass. It is well known that atomic detonations on or above a sandy desert will melt the silicon in the sand and turn the surface of the Earth into a sheet of glass.
Most of the sixty-plus volcanoes that erupt each year are low risk, however a combination of factors can cause a volcano to be a serious hazard. The factors causing these variations will be explained in this essay. The first factor that must be considered is the viscosity of the magma. This can determine how powerful an eruption is and what shape the volcano eventually becomes. Viscosity can be affected by three main factors, Firstly, the higher the temperature, the lower the density of the magma, causing it to flow more easily.
D. Scholar Geography 1 November 11, 2012 Test Corrections #1 Question: Which atmospheric heating process involves the emission of energy from an object? Correct Answer: E) Radiation My Answer: D) Why it’s Wrong: Radiation is the right answer because it has much stronger. It’s stronger than transmission, scattering, reflection and absorption. A good example would be: if your wearing a black shirt out in the sun you would be much hotter than if you’re wearing a white shirt. The black shirt would also fade over time because the suns rays would eat up the shirt.
Using the history of eruptions allows us to assess what is likely to happen in the future, for example, in the eruption of Mt. St. Helens in 1980 the volcano erupted on its side from a large bulge this left a huge crater as seen in the image. Because of this deep crater we know that neither a large debris avalanche nor a major lateral blast will like happen again. Mt. St. Helens is a very closely monitored volcano due to its previous eruptions.
While one might ask how water erosion can be so prevalent in the desert, it is important to note that like many Australian deserts, the area receives a surprisingly high amount of rain, about 200-250 millimeters a year. ("Ayers Rock Facts," 2009) It is believed that the mountain chains that once included Ayers Rock were as large as the surrounding peaks. Now, there is just one remaining piece of this long lost chain. Wind and water took an enormous toll on the surface of the area. When one considers other major mountain chains, and is informed that they were once much larger, it is hard to grasp the concept due to the fact that the mountains still exist, and are fairly large in their current state.
According to the same source, Iceland owes its existence to a large volcanic hot spot sitting on the mid-oceanic ridge. This being said, Iceland has a great number of volcanoes, and active ones at that. The most famous volcano in Iceland is Mount Hekla, which erupts magma. Hekla is still “very active”, according to the Iceland Total. It erupted in 1970, 1980, 1981, 1991, and the most recent eruption occurred in 2000 and lasted for 12 days.
Scientists have since seen these patterns as precursory to eruptions at many other volcanoes, including the 2004-2008 eruption of Mount St. Helens. At Mount St. Helens the value of an extensive system of seismic sensors has greatly improved our ability to determine the location and depth of earthquakes, and our ability to understand the physics of magma systems underground. The lack of short-term seismic or other geophysical indications in the hours and days prior to the May 18, 1980, debris avalanche, as well as prior to many short discrete explosions both before and after May 18, underscores that fact that scientists and public officials will not always have warning sufficient to issue short-term predictions of impending eruptive activity. Today, seismic
The largest shield volcano in the solar system is Olympus Mons, on the planet mars. Composite volcanoes can be identified by their symmetrical, wide-based shapes that consists of alternating layers of lava and cinder. Unlike any other type of volcano the composite volcano consists of both lava and cinder. The cone of a composite volcano is much steeper than the lava dome of a shield volcano. The cone of the volcano is formed partly by explosive eruptions of cinder.