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Describe the evidence for continental drift

Some of the geographical evidence collected in the last part of the 20th century to support the theory of the continental drift is the discovery of plate tectonics Hess and Deitz modified the theory called "Sea-floor Spreading".

In 1912 he first introduced the theory of the continental drift at a conference in Germany.

The theory of plate tectonics was developed from the theories of continental drift and sea-floor spreading and states that the earth’s surface is divided into several large plates, which are constantly in motion.

FREE Essay on Continental Drift Theory

Plate tectonics was developed through a theory once named continental drift.

As with previous critical events, , life helped terraform Earth. But the late Devonian is an instance when the rise of land plants may have also had effects. , which reduced the atmosphere’s carbon dioxide concentration by up to 80%, may have cooled Earth’s surface enough so that an ice age began and another one of Earth’s mass extinctions began. As with the , the ultimate cause for the Devonian extinctions seems to have been rising and falling sea levels, associated with growing and receding ice caps, as . Devonian extinction events began happening more than 380 mya, and a major one happened about 375 mya, called the . The reasons for the Kellwasser event are today generally attributed to the water becoming cold and anoxic.A bolide impact has been invoked in some scientific circles, but .Mountain-building and volcanic events also happened as continents began colliding to eventually form Pangaea (and the resultant silicate and basaltic weathering removed carbon dioxide from the atmosphere), and those dynamics may have been the previous major mass extinction. Black shales abounded during and after the Kellwasser event, and they are always evidence of anoxic conditions and how the oil deposits initially formed. However, the Kellwasser event anoxia may have not only been due to low atmospheric oxygen, but was also the result of eroding the newly exposed land and the detritus of the new forest biomes, which created a vast nutrient runoff into the oceans that may have initiated huge that caused anoxic events near shore.

After several million years of adaptation, tetrapods seemed ready to become the dominant land animals, but then came the second major Devonian extinction event, today called the . While the ice age conditions around the Kellwasser event are debated, there is no uncertainty about the Hangenberg event; there were massive, continental ice sheets, accompanied by falling sea levels and anoxic events, as evidenced by huge black shales. The event’s frigidity was probably a key extinction factor, and anoxia was the other killing mechanism. The Hangenberg event had ; it meant , the near-extinction of the (perhaps only one genus survived), oceanic went extinct, trilobites began to make their exit as seafloor communities were devastated, lobe-finned fish reached their peak influence, and forests collapsed.

Essay about Continental Drift - 678 Words

In developing plate tectonics, continental drift helped form hypothesis of a shifting landmass and sea floor....

Investigating the Cryogenian Ice Age led to finding evidence of runaway effects causing dramatic environmental changes, and the Cryogenian Ice Age’s dynamics will be investigated and debated for many years. The position of Antarctica at the South Pole and the landlocked Arctic Ocean have been key variables in initiating the current ice age, and another continental configuration that could contribute to initiating an ice age is , which and . A hypothesis is that can accompany supercontinents, so warm water is not pushed to the poles as vigorously. A supercontinent near the equator would not normally have ice sheets, which means that would be enhanced and remove more carbon dioxide than usual. Those conditions could initiate an ice age, beginning at the poles. It would start out as sea ice, floating atop the oceans.

Deep-ocean currents, , do not seem to have existed during supercontinental times, and atmospheric oxygen was likely only a few percent at most when the Cryogenian Period began. Canfield’s ocean-oxygenation evidence partly came from testing sulfur isotopes. As with , , and other elements, life prefers the lighter isotope of sulfur, and are two stable isotopes that can be easily tested in sediments. Canfield proposed that in pre-Cryogenian oceanic depths, , which are among Earth’s earliest life forms and produce as its waste product, abounded. Hydrogen sulfide gives rotten eggs their distinctive aroma and is highly toxic to plants and animals, as it . Hydrogen sulfide would react with dissolved iron to form iron pyrite and settle out in the ocean floor, just as the iron oxide did that formed the BIFs. The sulfate-reducing bacteria will enrich the sulfur-32/34 ratio by 3% and did so before the Cryogenian, but the Ediacaran iron pyrite sediments showed a 5% enrichment. A persuasive explanation is recycling sulfur in the oceanic ecosystem, which can only happen in the presence of oxygen.

In this essay I will be explaining what continantal drif is and discuss the arguments regurding continental drifting.
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whether some evidence is stronger link continental drift to plate ..

Also, the formation of Pangaea ( regarding what processes ) may have led to the dynamics that broke it apart. The Hawaiian Islands are that began forming more than 80 mya, and is due to a hotspot bubbling up from Earth’s mantle. Although the is , a prominent hypothesis is that the formation of Pangaea plugged hotspots and prevented heat from venting from Earth’s core, which led to a swelling and fracturing Pangaea. Part of the evidence for that hypothesis was relatively sudden and widespread volcanism sprouting up around Pangaea, which followed a known fracture pattern around such crustal upwellings. The volcanism and resultant fracture lines formed today’s continents. As can be seen in the during the late Permian, what became China and Siberia were on the northeast margins of Pangaea, bordering the Paleo-Tethys Ocean, and two volcanic events arising from China and Siberia are currently favored as key proximate causes of the Permian extinctions.

Free essay on Evidence in Support of the Continental Drift

Mass extinctions always have critical geophysical aspects to them, and often geochemical. Continental shelves under shallow seas, which are home to most marine life, are vulnerable to sea level and oceanic current changes. Stagnant waters, or waters that have too many nutrients dumped into them, can lose their oxygen, which triggers anoxic events that kill complex life. A continental shelf exposed to the atmosphere by a falling sea level would obviously lose its marine life, and that marine life might have had nowhere else to go. Sea levels can rise or fall for different reasons. The most obvious reason has been advancing and retreating ice sheets, as water is removed from or added to the oceans, but the aggregate continental landmass has always grown (possibly sporadically), continents can rise and can fall during the journeys of their tectonic plates, and the ocean’s collective basin has fluctuated in size, as water was hydrated into rocks, and also falling when and rising again as they fragmented. Generally, when , the continental shelves lost their marine life, and , anoxic conditions often accompanied them. There is evidence that the ozone layer has been periodically damaged, which stressed all plants and animals that the Sun directly shined on. The positions of the continents, both in relation to each other and their proximity to the equator or poles, can have dramatic effects, including impacts on global climate. Global climate changes and moving continents can turn rainforests into deserts and vice versa.

Continental drift theory supporting evidence for essays

The ecosystems may not have recovered from Olson’s Extinction of 270 mya, and at 260 mya came another mass extinction that is called the mid-Permian or extinction, or the , although a recent study found only one extinction event, in the mid-Capitanian. In the 1990s, the extinction was thought to result from falling sea levels. But the first of the two huge volcanic events coincided with the event, in . There can be several deadly outcomes of major volcanic events. As with an , massive volcanic events can block sunlight with the ash and create wintry conditions in the middle of summer. That alone can cause catastrophic conditions for life, but that is only one potential outcome of volcanism. What probably had far greater impact were the gases belched into the air. As oxygen levels crashed in the late Permian, there was also a huge carbon dioxide spike, as shown by , and the late-Permian volcanism is the near-unanimous choice as the primary reason. That would have helped create super-greenhouse conditions that perhaps came right on the heels of the volcanic winter. Not only would carbon dioxide vent from the mantle, as with all volcanism, but the late-Permian volcanism occurred beneath Ediacaran and Cambrian hydrocarbon deposits, which burned them and spewed even more carbon dioxide into the atmosphere. Not only that, great salt deposits from the Cambrian Period were also burned via the volcanism, which created hydrochloric acid clouds. Volcanoes also spew sulfur, which reacts with oxygen and water to form . The oceans around the volcanoes would have become acidic, and that fire-and-brimstone brew would have also showered the land. Not only that, but the warming initiated by the initial carbon dioxide spike could have then warmed up the oceans enough so that methane hydrates were liberated and create even more global warming. Such global warming apparently warmed the poles, which not only melted away the last ice caps and ended an ice age that had , but deciduous forests are in evidence at high latitudes. A 100-million-year Icehouse Earth period ended and a 200-million-year Greenhouse Earth period began, but the transition appears to have been chaotic, with wild swings in greenhouse gas levels and global temperatures. Warming the poles would have lessened the heat differential between the equator and poles and further diminished the lazy Panthalassic currents. The landlocked Paleo-Tethys and Tethys oceans, and perhaps even the Panthalassic Ocean, may have all become superheated and anoxic as the currents died. Huge also happened, which may have and led to ultraviolet light damage to land plants and animals. That was all on top of the oxygen crash. With the current state of research, all of the above events may have happened, in the greatest confluence of life-hostile conditions during the eon of complex life. A recent study suggests that the extinction event that ended the Permian may have lasted only 60,000 years or so. In 2001, a bolide event was proposed for the Permian extinction with great fanfare, but it does not appear to be related to the Permian extinction; the other dynamics would have been quite sufficient. The Permian extinction was the greatest catastrophe that Earth’s life experienced since the previous supercontinent existed in the .

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