Geological history of PA
The earth is an ever-changing chunk of rock to put it at the lowest level of comprehension available. This rock that we call home is brewing with billions of life forms and is constantly changing every day. This can be attributed to the various cycles that are at work on this planet of our, from the hydrological system to the rock cycle the earth is an ever changing form. Pennsylvania is just a small part of this system we call our home. Formed millions of year ago by tectonic collisions and molten rock Pennsylvania is a part of the earth full of specially minerals and geological features that stand out as being come of the best in the world. What would our state be with out its coalmines and steel mills. Which of course are only possible through the unique geographic features of our state. The Pre-Achaean, Achaean and Proterozoic Eras. Geologists believe that Pennsylvania was formed by parts of the Laurentian continental crust block. This crust block is made up of many micro plates, which were accreted during the period from about 2.5 billion to 1.0 billion years ago. This was previously part of an even larger crustal block called Rodinia. Geologist believes that PA is full of rocks that were once part of this crustal b
During this time period there were really two big events that shaped PA. The first big event during this time period was the large amounts of coal found in PA were created. This coal was created when the sediment supply decreased to the swamps that had formed; the swamps slowly disappeared leaving behind a whole lot of peat. This cycle of peat formation was what is responsible for all of the coal. The second big event in this time period was that it was the last time that marine waters of the Appalachian basin covered any part of Pennsylvania. Instead swamps with huge amounts of vegetation replaced the waters. This vegetation was possible because PA was so close to the equator at this time. This was also the time period when many animals started showing up including, amphibians, reptiles and air breathing mollusks. This period was a relatively slow time for PA until the end of it. This period saw more deposition of carbonate for a few million more years. It also saw the formation of the Acadian Mountains. These were formed just east of PA when there was a collision between a landmass called Avalonia and Europe. This collision was called the Acadian orogeny. Once these mountains were formed they became a chief source of sediments, which were deposited in the Appalachian basin. The first of these sediments that was deposited became the black and gray shale that extends all the way from eastern PA to western Ohio. Ultimately the Acadian mountains were completely eroded and the sediment that came from them pushed forward the Appalachian basin to the Ohio border. Much of this sediment can be seen today as red clastic rock. During this period the mountains that were formed by the Taconic orogeny were still a good source of sediments. PA was covered with clastic sediment form these mountains for the first half of this 25 million year period. Sand and gravel composed mainly of quartz were deposited by stream to the eastern parts of the state. There was also quartz sand carried further west and deposited on the beaches and shores. Even today some of this sediment can still be found along the linear ridges of the Ap
Some common words found in the essay are:
, Alleghanina Mountains, Cenozoic Era, Periods Carboniferous, Silurian Period, America Pennsylvania, Appalachian Mountains, Northern Hemisphere, Taconic Orogreny, Eras Geologists, appalachian basin, period period, taconic orogeny, mountains formed, pa taconic orogeny, sediment found, mountains eroded, period water, composed mainly, clastic sediment, period life, rocks greenville rocks,
Approximate Word count = 1435
Approximate Pages = 6 (250 words per page double spaced)
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