The United States Geological Survey - Dynamic Earth - Essay Example

? United s Geological Survey (USGS) Dynamic Earth Questions Introduction The Dynamic Earth: The Story of Plate Tectonics is a website written by Jacquelyne Kious and Robert Tilling, and published by the United States Geographical Survey (USGS). It is a comprehensive site which contains information about plate tectonics on earth, how the theory of plate tectonics was developed and what effect this has on occurrences throughout the world. It also contains detailed examples of how specific parts of the earth or geological events are directly related to plate tectonics. The site was published in 1999 and was developed from a paper published in 1996. Consequently, some of the information in the site may be out of date and it does not represent state-of-the-art research. Nevertheless, the site provides a valuable resource, and the information that it contains is important for understanding geological phenomena throughout the world. The Glomar Challenger and JOIDES Resolution The Glomar Challenger is a research vessel developed in the 1960s, which studies of marine biology, and had the ability to collect core samples from the deep ocean floor. The ship was involved in a scientific expedition in 1968 that provided important evidence towards the seafloor spreading hypothesis. In the 1990’s a ship was designed for the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES), named the JOIDES Resolution. This vessel is also focused on research, and has the ability to drill deeper than the Glomar Challenger and to produce higher precision positioning. The ship carries more than 9,000 meters of pipe for drilling (Kious & Tilling, 1999b). Having research vessels such as these allows researchers to develop extensive knowledge about the way that the processes within the earth interact, and what can be expected from these interactions. Major concentrations of earthquakes Throughout the world, earthquakes tend to be centered along oceanic spreading ridges and trenches. The most prominent of these are the Wadati-Benioff zones. The continental earthquakes that occur are highly concentrated in The People’s Republic of China. Additionally, there is also a high concentration of earthquakes in the Pacific Ring of Fire. This is a particularly relevant area as it is considered to be the world’s most seismically active zone (Kious & Tilling, 1999d). The majority of earthquakes in Europe are concentrated in the Caribbean region, and there are relatively few inland. Undersea hot springs In 1977, scientists discovered hot springs that occurred on the Galapagos Rift at a depth of 2.5 kilometers. This discovery was significant as it was the first such hot spring that had been found on the deep ocean floor, although their existence had been predicted since the 1970s. The remarkable fact about these (and other) undersea hot springs is that diversity and abundance of unusual sea life that lives surrounding these springs. For example, large clams and mussels as well as giant sea worms, were found around the 1977 system. Unusual bacteria have also been found in these systems that oxidize hydrogen sulfide. These provide the lowest level of the hot springs ecosystem, and they obtain their nutrients from the gases which exit the hot springs. Consequently, these areas represent a unique ecosystem, as the temperature of the spring can be up to 380°C (Kious & Tilling, 1999a). Plate boundaries The first type of plate boundary is a divergent boundary. This occurs where the tectonic plates pull away from one another and a new crust forms in the area where the plates had previously been. An example of a divergent boundary is the Mid-Atlantic Ridge, which spreads through divergent boundaries at the rate of 2.5 centimeters each year. Over millions of years, this has caused the gradual movement of the ocean floor, and equates to a rate of 25 kilometers in expansion every million years. The second type of boundary is a convergent boundary. This occurs when two plats move together and part of the crust is destroyed, as one plate dives under the other as the result of the collision. Convergence can occur in three ways. It can be between an oceanic and a continental plate, two continental plates or two oceanic plates. An example of a convergent boundary is oceanic-continental convergent that occurs in many locations on the Ring of Fire, and results in many volcanoes being sustained. One specific example of this is the Marianas Trench, which was formed from the collision of the Pacific Plate against the Philippine Plate. The next type of boundary is a transform boundary, or a transform-fault boundary. Here no crust is destroyed, but instead the two plates slide past each other horizontally. This type of boundary is generally found on the ocean floor, and result in the formation of zig-zag margins. An example of this that occurs on the land is the San Andreas Fault. Here, the Pacific Plate and the North American Plate are grinding past one another, moving at an average rate of five centimeters per year. This process has been occurring for an estimated ten million years. The final type of boundary is plate boundary zones. This is a broad belt of land where the boundaries between the plates are not well defined and it is difficult to determine how the plates are interacting with one another. Boundary zones tend to be much larger than other types of boundaries between plates, as it is generally not known where the boundary exists, or there are multiple to contend with. An example of this is in the Mediterranean-Alpine region, which is between the African and Eurasian Plates. This region also contains a number of microplates (smaller fragments of plates). Consequently, the interactions which occur in this region are complex and are difficult to predict (Kious & Tilling, 1999e). The Ring of Fire The Ring of Fire is a term that refers to the pattern of oceanic trenches and volcanic arcs that partially circles the Pacific Basin. The ‘ring’ is not a full circle as it does not close on one end. All the areas of the ring are closely associated with land masses, such as New Zealand and Argentina. This area experiences frequent volcanic eruptions and earthquakes, and is considered to be the most active area in the world volcanically and seismically (Kious & Tilling, 1999d). It is hoped that researching the interactions between the Pacific Plate and those that surround it, researchers will be able to understand more about what occurs during the buildup for volcanic eruptions and earthquakes (Kious & Tilling, 1999e). Hot spots While most volcanic activity and earthquakes occur at the boundaries between two plates, this is not always the case. The basic theory of plate-tectonics explains the way that volcanoes and earthquakes occur at the edges of plates; however, it does not explain how these events can occur in the middle of a plate, at a significant distance from any edge. Yet, there are many examples of volcanic activity that is not associated with a plate boundary. Hotspot theory predicts that there are small, localized areas below plates that are very hot and last a long time. These areas would be able to sustain volcanoes, and drive the creation of volcanoes and volcanic activity within a plate. Perhaps the most well-known example of a hotspot is the Hawaiian Islands. These islands were formed entirely from volcanic activity and are located more than 3,200 kilometers from the nearest plate boundary. Other prominent hotspots include Yellowstone National Park, Iceland and the Galapagos Islands (Kious & Tilling, 1999c). It is estimated that there have been more than 100 different hotspots present beneath the earth in the last ten million years. However, the authors of the website caution that there has been significant debate on hotspots since the original book was published, and new theories may now be present. References Kious, W. J., & Tilling, R. I. (1999a, June 24). Exploring the deep ocean floor: hot springs and strange creatures. This Dynamic Earth Retrieved April 2, 2012, from http://pubs.usgs.gov/publications/text/exploring.html Kious, W. J., & Tilling, R. I. (1999b, May 5). Glomar Challanger. This Dynamic Earth Retrieved April 2, 2012, from http://pubs.usgs.gov/gip/dynamic/glomar.html Kious, W. J., & Tilling, R. I. (1999c, May 5). "Hotspots": mantle thermal plumes. This Dynamic Earth Retrieved April 2, 2012, from http://pubs.usgs.gov/gip/dynamic/hotspots.html Kious, W. J., & Tilling, R. I. (1999d, May 5). Plate tectonics and people. This Dynamic Earth Retrieved April 2, 2012, from http://pubs.usgs.gov/gip/dynamic/tectonics.html Kious, W. J., & Tilling, R. I. (1999e, May 5). Understanding plate motions. This Dynamic Earth Retrieved April 2, 2012, from http://pubs.usgs.gov/gip/dynamic/understanding.html Read More