1st student project - Term Paper Example

Earthquakes Introduction The mid western continental united s has suffered a considerable number of earthquakes, many of them being of great magnitude, reaching upto or above 7 points on the richter scale. Several of these quakes were in the New Madrid zone which covers the areas of Illinois, Indiana, Kentucky, Arkansas, Tennessee, Missouri and Mississippi. The geological reasons to these earthquakes are not thoroughly clear as the region lies in the middle of a tectonic plate. This paper discusses the possible geological circumstances that could have lead to the earthquakes in midwestern US, and the evidence that proves the events of massive earthquakes in the prehistoric period.

Geological circumstances giving rise to earthquakes in mid western US The geological reasons given to most earthquakes are the movment of tectonic plates, causing damage when two plates overlap, slide under or over or past one another. The puzzling aspect about the mid western quakes is that they do not come under the areas affect by fault lines or cracks. There is geological evidence that this area was shook by earthquakes during the period of A.D 490, A.D 900 and A.D 1450, after which there were quakes again in 1811 to 1812.

The details imply a five hundred year pattern, under the theory that faults build up stress, causing these violent earthquakes as a let out. Another hypothesis that has been suggested as the reason behind the mid western quakes is the effect of ice glaciers from 20,000 years ago. Once the ice melted, lifting the load, the land began to rise but the mantle is not as flexible and takes longer to respond to the release of pressure. (findarticles.com). This is believed to have created unusual tension in the mid western continental United States, causing the New Madrid quakes.

Scientists have pinpointed a number of faults that have caused earthquakes over the midwestern region, shown in the map below. (Gambrell, 2008).It is also believed by scientists after 9 years of observation, that the New Madrid fault line might be shutting down, as it has shown no activity in the observation span. As a consequence, the risk calculations have varied wildly, from a 10 percent chance of a disastrous earthquake in the next 50 years to a chance of just 1 percent or less. (Choi, 2009).

Evidence for earthquakes in southwest IndianaThe Lower Wabash Valley of southwestern Indiana and adjacent parts of Illinois is seismically active. (Hill, 2002). There have been reports of earthquakes in parts of southwestern Indiana, affecting different parts in the years 1968, 1987 and 2001. It has been noted that the Lower Wabash Valley is capable of causing disastrous earthquakes at any time. Geological evidence exists that there have been prehistoric earthquakes of great intensity in the southern Indiana region and the southeastern Illinois.

The map below shows the historic seismic activity in the Southwestern Indiana and eastern Illinios region. (Indiana.edu).The liquefaction seen in the areas and the fracture that sandy soils flow upward in, known as dikes , that are formed as a result of earthquakes help determine the intensity and period of the quake. Along the east bank of Wabasch river, Steven Obermeier found a major liquefaction. The gravel and sand from the Wabash river were thrown up in liquefaction, hitting a tree that grew on the bank.

When the tree was studied, it is seen to date 6100 years ago, proving that earthquakes of great intensity have been seen by the area of south western Indiana in the past. It is believed that it was a magnitude 7 earthquake. From field evidence at this and other sites in southwestern Indiana, we know that the Lower Wabash Valley is capable of producing large and potentially damaging earthquakes. (Hill, 2002). ConclusionThe mid western continental United States may be subject to more major earthquakes in the region.

However, scientists believe that the fault in the new Madrid region might be shutting down, lowering their risk. The southwestern Indiana region, however, maybe subject to disastrous earthquakes in the future, with evidence of prehistoric earthquakes and the fact that recently a number of quakes have been noted.ReferenceChoi, C.Q. (2009). Are mid-western earthquake faults shutting down? Retrieved April 16, 2010 fromhttp://www.scientificamerican.com/article.cfm?id=rumble-offfindarticles.com. (2001).

Midwestern Earthquakes? —Blame Old Glaciers - Brief Article - Statistical Data Included. Retrieved April 16, 2010 fromhttp://findarticles.com/p/articles/mi_m1272/is_2673_129/ai_75496832/.Gambrell, J. (2008). Newly found fault can cause US quake. Retrieved April 16, 2010 fromhttp://www.greatdreams.com/madrid.htmHill, J. R. (2002). Earthquake near Evansville, another warning of things to come. Retrieved April 16, 2010 fromhttp://igs.indiana.edu/geology/earthquakes/preparedness/index.

cfmindiana.edu. Historic seismic activity map. Retrieved April 16, 2010 fromhttp://www.indiana.edu/~pepp/earthquakes/images/wabash1_3_03/usgshistorical .jpg