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Effects of volcanoes on the environment
Essay on volcanoes effect on climate change
Essay on volcanoes effect on climate change
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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.
15. The pictures above show how the continents on Earth’s surface have changed position over a very long period of time. What explains this change? (S6E5e, f)
Since measurements began in 1958 -- and it can be assumed to have been the case since the industrial revolution -- emission of carbon dioxide into the atmosphere has risen steadily as a result of the burning of fossil fuels (Quay, pp 2344). Although there is much argument over the implications of increasing carbon dioxide levels in the atmosphere, there are several points that almost all scientists would agree on: firstly, carbon dioxide acts to absorb radiated heat; if present in our atmosphere will do just that to some extent. Second, the concentration of carbon dioxide in our atmosphere is rising. Third, the temperature of the planet is rising - although the amount of this increase and the causes of this rise are subject to disagreement (Philander, pp 193).
After the Laramide orogeny things were still happening, just as always with Earth. Something is always changing even if it is not detectable day by day. Due to the Farallon Plate subducting there was a suction like effect going on because of the water that was being taken in with it (Humphreys). This would cause the North American plate to become weak and unstable, because it was being hydrated. This eventually would result in large plateaus and large amounts of uplift (Humphreys). There are many things that have been going on through out this time period but it all turns around and creates and shapes the earth into what it is today as well as what it will be in the future.
The present climate change is mostly human induced; the increase in CO2 is mainly because of human activities. Activities like changes in land use pattern, deforestation, land clearing, agriculture, and other activities that have all led to a rise in the emission of carbon dioxide.
By the Carboniferous period (~359-299 Mya) Anglesey had passed the equator. The environment here was shallow marine and Carboniferous Limestone was formed. 255mya all continents managed to collide forming one supercontinent, Pangea. At this moment in time Anglesey was located in the Northern hemisphere.
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.
...t of laurasia, just like most of the other plates. North America,Europe, and Green land all used to be connect because of Pangea ( as mentioned earlier). But when everything started to separate, first europe, then green land, and lastly the North American plate. After pangea was no more and the plates all started moving, the continents started going their own ways, there fore putting the continents where they are today.
Han, J., Zhang, Z. F., & Liu, J. N. (2008). A preliminary note on the dispersal of the Cambrian Burgess Shale-type faunas. Gondwana Research, (1), 269-276. doi:10.1016/j.gr.2007.09.001
One of the most compelling and difficult environmental problems society faces today is climate change. People do not realize how much the environment has changed for the worse in the last ten years, until they are told that the last two decades of the 20th century have been the hottest in the last 400 years, according to climate studies (Conserve Energy Future). Today, the carbon dioxide levels have reached 396.81 parts per million (ppm). “Carbon dioxide (CO2) has also increased over the last 100 years-- from about 300 ppm to 370 ppm. Interestingly, the majority of these additions have occurred in the last 50 years, when temperature increases have been the slowest” (geocraft).
There are several theories about how the Cambrian Explosion started. There were major changes in marine environments and chemistry from the late Precambrian into the Cambrian, and these also may have impacted the rise of mineralized skeletons among previously soft-bodied organisms. One theory as to what happened is that oxygen in the atmosphere, with the contribution of photosy...
...deposition and blanket of sediment kept the organisms compressed with little exposure to oxygen for decay. If life was predominately terrestrial during the Cambrian, the organisms predictably would have been left untouched after death long enough to decay, preventing the fine preservation of many soft-bodied organisms. Fortunately enough, it was marine life that dominated the Cambrian (Scott, et al., 2000).
About 320 million years ago, precursors of Pangea Laurussia (combined Scotland, Greenland, North America and Russia) and Gondwana ( which was the rest of the earth's land mass ) converged and made a Godzilla continent surrounded by the huge panthalassic ocean. The collisions of Laurussia and Gondwana raised a mountain belt, present-day remnants of which are the Appalachians along North America’s eastern coast and highlands in central Europe. By 135 million years ago (dang plate tectonics, you move slow ) the breakup of pangea was well under way. Rifting and seafloor spreading opened the nascent North Atlantic Ocean between North America and the old continent Gondwana, in which South America and Africa were still Jointed. So wasn't that nice