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From: Josh
Date: 11/18/02
Time: 5:11:42 PM
Remote Name: 205.188.209.101
Here is what our sphere group came up with last week on the lithosphere.
What is the Lithosphere? The lithosphere contains all of the cold, hard solid land of the planet's crust, the semi-solid land underneath the crust and the liquid land near the center of the earth. The surface of the lithosphere is very uneven and divided into several layers. The solid, semi-solid and liquid land of the lithosphere of the earth can be pushed and deformed like silly putty in response to the warmth of the Earth, such that the rocks actually flow. The flowing lithosphere carries the crust of the earth, including the continents, on it's back. The rocky material that comprises the lithosphere of the earth is special, however, because the rocks contain water. These special minerals have the ability to slide against each other. The lithosphere is divided up into approximately 14 pieces called tectonic plates. These plates slide over the semi-molten layers below and form the continents and ocean basin. The process of moving plates is known as the Plate Tectonic Theory. Many calculations about the earth are needed to know the thickness of the lithosphere. Some assume that it is 120km, while others think it is closer to 250km. A study by Manga and O'Connell shows that the lithosphere probably has a variable thickness -250 km under continents and 100 km under the oceans.
What are Hurricanes?
A hurricane is a violent, spiraling tropical storm with fierce rotating winds and a calm central eye, usually develops over warm tropical seas, these storms are known as hurricanes in n the Atlantic Ocean, The Caribbean Sea, or west of the international dateline in the Pacific Ocean. In a mature hurricane, wind picks up warmth and moisture from the ocean, circling inward ever faster from outer cloud bands to inner eye wall, where winds are the strongest and where it finally rises rapidly and is pushed out the top. Most hurricanes that hit the United States begin either in the Caribbean or the Atlantic. In the beginning, a disturbance forms in the atmosphere, developing into an area of low atmospheric pressure. Winds begin to move into the center of the storm seedling from surrounding areas of higher air pressure. Warm water heats the air, and it rises as it nears the center. The ocean feeds warmth and moisture into the storm, providing energy that causes the warm air in the center to rise faster. It condenses high in the atmosphere, creating thunderstorms. The tropical depression develops into a tropical storm, and then finally into a hurricane, which is not unlike a giant swirling mass of thunderstorms. As rising air in the storm's center condenses, it produces heat, forcing it to rise even faster. The air is pushed out the top and more air has to rush in at the surface to take its place. This kicks the ocean up more and, the storm essentially feeds on itself. The Hurricane winds blow hard. In fact, they have to blow at least 74 miles an hour or a storm isn't even called a hurricane. But once a storm has enough wind speed to be called a hurricane, that's not the end of the story. One day it might be blowing 100 miles an hour and the next day 80. Then three days later it might be blowing 120. Hurricanes have the potential to spin off tornadoes, giving a one-two punch to coastal regions. Many tornadoes form in the right-front quadrant of a hurricane. Ground winds ease slightly once a hurricane hits land, but winds at 5,000 feet blow harder. This causes the air to spin around a horizontal axis. A tornado forms when rising air tilts these horizontal rolls into vertical columns of air. http://www.news-record.com/news/indepth/krt/html
Hurricanes are among the strongest climatic events on earth. It is type of tropical cyclone. This is a generic term for a low-pressure system normally forming in the tropical regions. This type of cyclone is accompanied by thunderstorms and in the Northern Hemisphere, a counterclockwise circulation of winds. The Atlantic hurricane season is June 1st through November 30th. http://www.hurricanes2000.com/FAQ.html http://www.miamisci.org/hurricane/howhurrwork.html
Event to Sphere Interactions:
E>L Hurricane force winds can also affect the lithosphere. The high winds associated with the hurricane can result in erosion the beaches and the surrounding area. Debris such as roofing material, siding and small items left outside become projectiles during the storm. The blowing debris will also damage the top layer of the lithosphere. The multiple layers of the earth's lithosphere will continue to be worn down by the trees and other plant life will be uprooted, damaging the lithosphere.
E>L The short-term evolution of landforms along a coastline represents the interaction of wave action with processes in the continental interior and human activity. The coastline is a dynamic environment that advances or retreats depending upon the balance between the supply of sediment and the material removed by wave erosion. This balance may upset by geological processes that act at a variety of time scales. Seasonal variations in stream flow and storm activity affect the volume of sediment supplied to the coast and the rate of erosion. Climate cycles that result in increasing or decreasing sea levels will have long term effects measured in decades or centuries. Finally, tectonic cycles measured in hundreds or thousands of years may continually revitalize rugged coastlines by periodic uplifts. The role plate tectonics plays in influencing the physical character of the coastline is exemplified by the contrast between the sandy beaches of the Atlantic shore (passive margin) and the rocky headlands of the Pacific coast (active margin). Some areas in the Gulf of Mexico coastline are actively subsiding. Sediment deposited in a delta at the mouth of the Mississippi River is submerged below sea level during compaction. Subsidence rates are approximately 1 meter per century. In the past this subsidence was compensated by additional sediment supplied during flood events. However, the construction of levees along the river’s channel prevents the redistribution of sediment during flooding. http://www.mhhe.com/earrhsci/geology/mcconnell/oceans/coast.html
E>L Storm surge flooding is a major cause of hurricane damage. Howling winds around the hurricane create storm surge by piling water up. In the ocean, this dome of water sinks and follows as the storm nears land, the rising sea floor blocks the water’s escape and it comes ashore as a deadly intense hurricane can send a dome of water more than 18 feet deep ashore as the storm hits land. This sudden dropping of water onto beaches causes erosion and gully formation. http://www.usatoday.com/weather/tg/wsurge/
E>L: Strong winds from a hurricane can spread vegetation and soil for miles around. The soil can be spread locally and also farther inland. This can have positive and negative effects. On the positive side, soil and vegetation can be spread elsewhere bringing newfound life. On the negative side, a rich soiled site can be ripped bare by torrent winds of a hurricane. http://davem2.cotf.edu/mtpe/courses/idaho/ievents/0038.html
E>L: Huge mounds of water imploding on the earth’s surface called “storm surges” can cause severe beach erosion. These implosions of water can also cause temporary and permanent changes in water channels and other waterways. Other effects of this are shoreline changes, movement of soil vegetation, and further extensive flooding. http://davem2.cotf.edu/mtpe/courses/idaho/ievents/0038.html ge.htm