Earth Structure and Formation

1. Summarize advances over time in determining the age of the Earth, including the importance of the discovery or radioactivity.

Some of the advances over time in determining the age of the earth were that back in the 450 B.C.E. the Egyptians digged trenches along the Nile River because the Nile deposits a layer of sediment every year, so they went in and counted the layers and they were able to identify 5,000 different layers and figured that the earth was at least 5,000 years old. Others such as people in the middle ages often used sacred texts like the bible in order to determine the age of the earth. During the 18th and 19th century people used variety of techniques. Those techniques were to look at the salinities of the oceans, the rates of sedimentation and models in order to figure out the age of the earth. The importance of radioactivity is that it plays a big role. Radioactivity provides heat that keeps our planet going. In other words we owe our existence to the radioactive decay of three elements, uranium, thorium, and potassium. If not for radioactive decay of these elements, we would not exist, because life would not be here and the planet would be a dead cinder floating in space, no oceans, no atmosphere, no plate tectonics and no continents. All of these exist now because of the slow decay of radioactivity.

2. What makes Earth a habitable, relatively stable environment within which we exist and survive? Review the early development of the solar system, including the Big Bang theory, to support your answer.

Earth is habitable because of its location in the solar system. It is the goldilocks zone where water is liquid. The gridlocks planet is where the planet falls within a stars habitable zone and this name is used for those planets that are close to the size of earth. The habitable zone is the intersection of two regions that are favorable of life. The one is within the planetary system and the other is within the galaxy. The solar system has many candidates' habitable worlds and they do not exhibit the full breadth of phenomena that we find on earth. Also the liquid water once flowed on Mars; Europa, a moon of Jupiter is to have sub surfaced liquid water ocean which has been covered by a thick layer of ice. However in order for habitable worlds we must find starts at the right stage of their life cycle, and of suitable spectral type.

3. Alfred Wegener was a polar explorer and visionary. Describe how his early work was viewed with skepticism and how ultimately his theory on continental drift was proven. What kinds of evidence did Wegener rely on to substantiate his continental drift hypotheses (Pangaea).

Alfred Wegner once said that all our present continents had once been together as a large super continent that he called Pangaea and that these continents had broken apart. He stated that not just did the continents fit together, but he said look at the different rocks, and that you will find the same ricks on the west coast of Africa and the east coast of South America. He stated that most of the rocks formed when the continents were together. He said that you can find fossils, plants and animals, organisms that lived 250 years ago on parts of India, Africa, Antarctica, and South America. His point on this view was that they must of have been at one point because these plants could not have floated across the ocean, and these animals could not swim. However, Alfred Wegener shot himself in the foot because come to find out he was a weather man and he did not understand things like rocks, and flow and geophysics, so he came up with the idea that the reason these rocks were moving was because they were fleeing the pull from some centrifugal of tides from the sun and the moon broke them apart or that they once were moving, their own momentum would move them. To prove his theory he citied many examples including the apparent fit between the coastlines of South America and Western Africa as well as North America and Northwestern Africa. He also stated that the existence of rocks apparently gouged by glaciers in South America and India far from the modern day glacial activity. He even showed that Greenland was drifting slowly away from Europe. Wegner theory was right, but had one short come and that was that there was no explanation of exactly how the continental drift had taken place.