5 billion years or more -- according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries. How then do scientists reckon geologic time, and why do they believe the Earth is so old? A great part of the secret of the Earth's age is locked up in its rocks, and our centuries-old search for the key led to the beginning and nourished the growth of geologic science.
Geologic time is often discussed in two forms: .
• Relative time ("chronostratic") -- subdivisions of the Earth's geology in a specific order based upon relative age relationships (most commonly, vertical/stratigraphic position). These subdivisions are given names, most of which can be recognized globally, usually on the basis of fossils. .
• Absolute time ("chronometric") -- numerical ages in "millions of years" or some other measurement. These are most commonly obtained by using radiometric dating methods performed on appropriate rock types. .
Some of the most important discoveries of modern science and technology have been the discovery of the Earth's age and the vast length of time encompassed by its history. This scale, comprised of billions and trillions of years is called the geologic time. In the mid-17th century an Irish clergyman, Bishop James Usher, added the years in the biblical genealogies and concluded that the Earth was created in 4004 BC. This idea persisted for a long while, although the 18th-century French scientist Georges Louis Leclerc, Comte de Buffon, reasoned that the Earth cooled from an originally molten body and that this would have required at least 75,000 years. .
Buffon had to recant, but development of the principle of uniformitarianism in the late 1700s and early 1800s provided geologists with new grounds for arguing that the Earth is far older than anyone had imagined.
Florida turned into its current shape during the Cenozoic Era. During this time, sea levels dropped and Florida rose from the ocean. ... After the Cenozoic Era, the Oligocene Era created deposits of clays and sands because of the fluctuations in sea-levels. ... The Keys at this time became islands and coral reefs were formed. ... This is the general geology of how Florida became Florida. ...
What is unique about the canyon's geology is the great variety of rocks present, the clarity with which they're exposed, and the complex geologic story they tell (Anonymous, 2000; p. geology). ... Therein lies the geological appeal of the canyon. ... This arrangement of conditions - a geologically young canyon cut through geologically old rocks - provides a setting in which there is contained two separate geologic stories. The older of the two, revealed in the rocks exposed in the canyon's walls, provide a record of several eras. ... "During this time, the North American craton...
Cenozoic Era, last of the five major eras of geologic time, beginning about 65 million years ago and extending through the present. The Cenozoic, shortest of the geologic eras, is that period during which the modern world, with its characteristic geographical features and its animals and plants, came into being. Paleontologists often call the Cenozoic the age of Mammals because mammals became common during this time. ... This era is sometimes called the Age of Man because the earliest humans are believed to have evolved then. ... All eventually faced a changing environment as time progress...
Washington State has a very interesting geologic history as does the rest of the Pacific Northwest. ... The Paleozoic Era was a quiet one, in which Washington experienced little action. ... Pangea brought the continents back together and formed another super continent during the later half of the Paleozoic Era. ... Eventually, Washington is buried in sediment mostly sand and silt, which preserved fossils of the time, which include palm trees, which give the coast a tropical setting of that time period. Finally there is the Cascade Episode, which brings us up to present time. ...
History of the Earth What has happened through earth geologic history? ... By looking at a stacked arrangement of rocks scientists can determine the age of fossils and rocks called a geologic column. Through this geologic column scientist have been able to break the earth's history down into different periods of time. ... Scientists have given names to these certain points of time or eras in history. ... The Paleozoic era is broken up into many periods because the amount of life during this time. ...
Geological Survey after the Civil War unified the major geological surveys around the country, and providing standard rules and guidelines to overzealous and failing expeditions. ... King brought new scientific techniques into use and was driven by exacting perfection created a detailed account of his travels, yet many believe he covered a huge expanse of land in to short a time. ... Powell coined several geological terms and was one of the first in what is now called geomorphology. ... The United States Geological Survey was created to create an ongoing study of geography. ... The United ...
The spectacular exhibits from all over the world offers a remarkable insight, from the era of dinosaurs to the era of space exploration. When entering the museum, one learns important concepts that derive from Geology, Chemistry, Physics and History. ... we also saw a diversity of fossils from Amphibians, reptiles from each era. ... There was also a Geology exhibition, in which one can learn the major events of evolution of the Earth and life. ... My son and I had a great time watching theses events on the computer. ...
I started at the geological exhibits and learned that the geode is the state rock. ... Over time, the outer shell of the spherical shape hardens, and water containing silica precipitation forms on the inside walls of the hollow cavity within the geode. ... (http://www.desertusa.com/magjan98/jan_pap/du_rock_geode.html) Other Geological Findings From My Adventures Iowa soil and rock has formed over millions of years of geological processes.. ... The limestone comes from a time when Iowa was covered in sea water and was nothing but as sea floor for the world (hard to imagine). ... The sh...
