James Smitt
12-7-12

Geology 1040

The two main books that were read and evaluated in this paper were first, “Adventures through Deep Time: The Central Mississippi River Valley and Its Earthquakes,” and second “Arkansas Review: A journal of Delta Studies.” Through looking and glancing at these two books, it explains the geologic structure of the Mississippi Valley and how Mississippi and Arkansas relate to it. It also discusses fault lines, and the earthquakes around the Mississippi and Arkansas regions. In the first book that I read, it started off reading the first chapter when it discusses the basics of the central Mississippi River Valley starting with the Precambrian time scale. During this period, North America was formed by different continents that were formed from the many tectonic plates over time. Most of the Precambrian rocks in the Mississippi Valley are metamorphic rocks. Before any of this, there was only one gigantic piece of land called Pangea. At that time all of the world’s continents were together, and over time the plates slowly shifted away from each other and eventually forming the different continents of what we know today. The only set back of the Precambrian time is that the rocks that were formed then now are buried deep within the soil and ground. It is very for geologist to study these rocks. The earth’s crust beneath the Mississippi Valley has a thickness of about 42 km. A later chapter that was very interesting was the chapter that discussed how Pangea ripped apart. When Pangea was tearing apart over time, it formed to what is to be called the Gulf of Mexico. There the water of the Mississippi River flows from as far as southern Canada, all the way into the Gulf of Mexico. Many types of sediment rocks poured into the Gulf of Mexico from many important streams that stretched all over Texas during the Paleocene period, through the Oligocene period. It later shifted to the Mississippi River Valley from the Miocene to present day. The end result of the Mississippi River Valley was that it made and transformed the Gulf of Mexico to 300 km of seaward growth. The Mississippi River today starts at Lake Itasca and has an entire length of 2,530 miles. In the late Cretaceous period, the sea level connected the Gulf of Mexico to the eastern part of the Rocky Mountains. Over time, the sea level dropped at the end of the Cretaceous. One thing that amazes geologists about the Mississippi River is the Mississippi Embayment. This Embayment is a landscape of flat river floodplains and low rolling hills. Deposition occurred intermittently during the late Cretaceous period through the Oligocene time. Even though the sea level was higher globally during Late Cretaceous time, the sea rise itself cannot explain the origin of the Mississippi Embayment. One of the most shocking aspects of the Embayment is that is sediments truncate and overlie the denuded Appalachian-Ouachita Mountain system. The second book that was read dealt with the pages 131 to 135. In these pages, it mainly discussed the perspective of a geologist on the Mississippi River. It talked about how the Mississippi Delta is around four hundred miles in length. It has many resources to give to the general public, especially to the people who live along the Mississippi River. The Delta begins in the Cairo, Illinois, all the way to the Gulf of Mexico. The geologist explains how it also had a literary, musical, sociological, economic, and ecological impact. From looking at the Delta, it is very remarkable because of its flatness. In the United States, the center of it is flat and completely the opposite on the western and eastern sides with hills and Rocky Mountains. Later in the chapter, it then talks about how over a long period of time the Gulf of Mexico used to be actually in the United States. Most of the south eastern part of the country would be underwater and uninhabitable. A good consequence from that happening was the rich and fertile grounds that we live on every day. The Delta is a pile of multiple things including, gravel, sand, and mud. The Gulf of Mexico started forming around two hundred million years ago, separating Pangea. This place was called Gondwana when Pangea still existed. The large remains however are now parts of Florida and Louisiana. Later with in the chapter, it talks about there is a possibility of volcanoes erupting within the Mississippi Embayment and Reelfoot Rift because of the soft ground made up from the gravel, sand, mud from the northern parts of the country. The Bermuda hotspot is what started the forming of what today is known as North America. Once the Northern part of America formed, it had a warm and tropical climate. But as time continued, it began to cool because of the continuation of the North American plate moving closer to the North Pole. It also explained how the six mile wide asteroid fell from the sky and pretty much created the Gulf of Mexico or simply expanded deep into the North American plate. As time rolled on, the sediment finally reached Louisiana. It took the Gulf of Mexico about 25 million years to reach back into what it is today. Through reading the two books that were assigned, it talked mainly about the Mississippi River Valley. It explained its beginning and how it began to what it is today. It also showed the geologic structure and how the different types it went through in order of becoming a very important system of travel and resources through the United State today. It is clear that the end of this is not over and who knows what it will be like in the near or distant future.