ORDOVICIAN PERIOD
The Ordovician Period is the second period of the Paleozoic Era and began 485.4 million years ago and ended 443.4 million years ago (when the Silurian Period began). Four continents were present and separated by three main oceans. Laurentia was composed of present-day North America, part of Scotland, and Greenland and was near the equator. Siberia-Kazakhstan was east of Laurentia, slightly north of the equator. The Iapetus Ocean separated these two masses on the south from the continent of Baltica. Avalonia (England, New England, and parts of Canada) was to the west of Baltica. England, Baltica, and Kazakhstan were separated from Gondwana by the Paleotethys Sea. At this time, Africa and South America were rotated almost 180° from their current location. The Panthalassic Ocean covered the Northern Hemisphere almost completely.
The rate of seafloor spreading was minimal during the Ordovician Period but thanks to high oceanic ridges, the seafloor became elevated and many parts of the continents were flooded. Shallow seas within the continents were thus formed. Sea levels fluctuated constantly maybe due to the rates of plate motion, ice caps, etc. The major tectonic plates were moving during this period so volcanism was extensive, peaking twice during the early Paleozoic Era. Mountain building belts were created wherever plates converged as well.
The levels of carbon dioxide in the atmosphere were 15 times higher than they are today and this was due to the volcanic activity, which released enormous amount of carbon dioxide gas into the atmosphere. The flooding of continents and the lack of plants on land also contributed to the heightened levels. These conditions created a greenhouse effect so tempera...
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...nd Stromatoporoids (a kind of sponge with a layered skeleton) were common rock builders of the Northern Hemisphere. Moss was common in shallow seas. Among the arthropods, the giant eurypterids (sea scorpions) have been found in the Old Red Sandston facies (see image above). The first insect was part of a group of wingless insects that feed off of debris and soil. Conodonts were vertebrate animals abundant in marine life. Many of the fish were heavily armored and the earlier fish (agnathans) had no jaws and were mud eaters and scavengers. Chondrichthians are sharklike fishes that were first found in the Middle Devonian. In terms of plants, many vascular plants emerged and a varied flora was established. There is evidence of algae, bryophytes, and charophytes. Algae and fungi also existed. As previously stated, the first known forests are from the Devonian Period.
A significant portion of New England was formed as a result of an accretionary orogen. Southeastern New England is marked by a series of terranes that accreted onto the Laurentian supercontinent during the Silurian and Devonian. The Terranes of Gander, Nashoba, Avalon, and Meguma are present from west to east in eastern Massachusetts and all of are Gondwanan provenance. Their modern-day juxtaposition suggests that the marginal Gondwanan micro-continents collided sequentially from west to east, expanding the Laurentian continent with each respective collision. As each subsequent plate collided, an intervening subduction zone died and a new subduction zone was created to the east. The oblique collision of the Avalon Terrane into Laurentia followed the accretions of the Gander and Nashoba Terranes and preceded the accretion of Meguma. The collision was marked by uplift, mylonitic metamorphism, and calc-alkaline Nashoba plutonism as the Iapetus Ocean subducted under the Nashoba and eventually the Avalon collided obliquely into the continental margin.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
...silophodon, a small, agile bipedal herbivore. The Ceratopsians appeared at beginning of cretaceous period from the family Ornithopoda. Pachycephalosaurs contained a ten inch thick skull, which was actually fairly fragile, and their first line of self defense would be to run away. Ceratopsians, which mean horned face, are large beasts with horns that can defend themselves pretty well. Both were very similar, but contained distinct differences.
One of the main causes of the increase in Earth’s temperature is greenhouse gases. Greenhouse gases are gases that are trapped in the atmosphere. The gases consist of carbon dioxide, nitrous oxide, and methane. They trapped heat from the sun from returning back into the atmosphere. Over the last 100 hundred years we have increased the earth’s average temperature by 1.4 degree fahrenheit (Carey). This is mainly due to the fact we are producing ten times more greenhouse gas than before. It is exp...
About 20 million years ago the last part of the Farallon sea floor plate subducted under the North American plate. This put the North American plate and the Pacific plate into contact, but unlike the Farallon sea floor plate, the Pacific plate sheared against the side of the North American plate. Because there was no plate subducting, the North American plate was in direct contact with the mantle (Tierney, 29). Heat from the mantle made the continental crust more ductile, which allowed the crust to extend and thin.
During the Devonian period (~390mya), Anglesey drifted toward the equator. Anglesey, (including Ireland, England and Scotland) as a result endured hot, arid, terrestrial conditions. Rocks, such as old Red sandstone were formed as a result and can be seen in Anglesey
"Climate and CO2 in the Atmosphere." Climate and CO2 in the Atmosphere. University of California, San Diego, 2002. Web. 26 June 2014. .
Summary: After the formation of the Earth, continents, once apart of a single supercontinent, slowly move away from one another. The shifting and movement of the continents created geographical landmarks such as mountains and large oceans. Later, enormous sheets of ice covered large areas of the Earth in a period known as the Ice Age. When the ice retreated from North America, it left the landscape as we know it today.
The Jurassic period was the second segment of the Mesozoic Era. It occurred from 199.6 to 145.5 millions years ago, following the Triassic Period and preceding the Cretaceous Period. During the Jurassic Period, the supercontinent Pangaea split apart. Laurentia, the northern half, made up what would eventually form North America and Eurasia. The creation of these opened basins for the central Atlantic and the Gulf of Mexico. The southern half, Gondwana, drifted into an eastern segment that now forms Antarctica, Madagascar, India, and Australia, and a western portion that forms the present Africa and South America. This rifting, along with generally warmer global temperatures, allowed for diversification and dominance of the reptiles known as dinosaurs. Along with dinosaurs, several different types of life and rock formations emerged during the Jurassic period.
The Permian Period occurred around 298 million years ago. It stretched from the Carboniferous Era to the Triassic. Sir Roderick Murchison in the early 1800’s noticed a differentiation among the overlay of the rock formation in the Ural Mountains in Russia. These rocks differed from the older Carboniferous rocks in Britain, and seemed younger than the Triassic rocks of Europe. Murchison named this differentiation after the prehistoric kingdom of Perm, thus the Permian Period.
In addition to ample global shifts, many important regional activities occurred. The continents of North America and Europe collided, resulting in massive granite formations as well as the formation of the Appalachian Mountains located on the eastern side of the North American continent. Extensive reef building produced some of the world's largest reef complexes (“More Info about the Devonian World”). These reefs were built in the equatorial seas between the two preexisting cont...
Throughout history climates have drastically changed. There have been shifts from warm climates to the Ice Ages (Cunningham & Cunningham, 2009, p.204). Evidence suggests there have been at least a dozen abrupt climate changes throughout the history of the earth. There are a few suspected reasons for these past climate changes. One reason may be that asteroids hitting the earth and volcanic eruptions caused some of them. A further assumption is that 22-year solar magnetic cycles and 11-year sunspot cycles played a part in the changes. A further possibility is that a regular shifting in the angle of the moon orbiting earth causing changing tides and atmospheric circulation affects the global climate (Cunningham & Cunningham, 2009, p.205). Scientific studies suggest that all these played a role in past global warming and cooling periods. Today, however, there is a lot of conflict on whether humans are causing a global warming that could be disastrous to humans and all species of plants and animals on this earth. This paper will first explain the greenhouse effect, then take a look at both sides argument, and, finally, analyze the effect of global warming on world-wide sustainability
The Hellenic and Hellenistic eras of ancient Greece brought forth new ideas in scientific innovation, art, philosophy, agriculture, warfare, and government. Hellenic Greece heralded leaders such as Pericles and Cleisthenes as well as the philosophers Socrates and Plato and playwrights Sophocles, Aeschylus, and Euripides. The Hellenistic era boasted the influence of Alexander the Great’s great empire from the Mediterranean to India, and the spread of Greek culture and knowledge to the conquered lands. The Roman war machine and the death of Cleopatra VII eventually brought an end to the Hellenistic era, but the Hellenistic and Hellenic eras’ continued to make a lasting impact on the future of humankind. Even the Romans became envious of Hellenic
“For centuries, atmospheric carbon dioxide has never been above” about three hundred parts million. However, in the 1950s it had reach about four hundred parts per million (Global Climate Change). The large spike of carbon dioxide levels could be explained by the Industrial Revolution. The Industrial Revolution lasted around until the 1870s and not only “redefine how people earned a living” but was a the leading cause of increasing carbon dioxide levels in the atmosphere (Marshall “Industrial Revolution”). Wind and water driven mills were no longer constrained to rivers and windy areas and was freed by the use of coal. Coal allowed industries to pop up anywhere and everywhere rather than sticking around coastal areas and by main ports. The availability to have factories function anywhere ramped up the use of coal, thus sending carbon levels sky high.
Schmidt, G. A., R. A. Ruedy, R. L. Miller, & A. A. Lacis (2010), Attribution of the present‐day total greenhouse effect, Journal of Geophysical Research, 115, D20106, doi:10.1029/2010JD014287.