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Throughout the past 40 million years our Earth has been in a continuous ice age. This period is considered an ice age because of the ongoing presence of an ice sheet that currently covers Antarctica. An ice age can be thought of as a period of time where the Earth’s climate is constantly reducing in temperature, which causes the formation of ice sheets and glaciers. This cooling of the Earth doesn’t happen all at once, it goes through cycles of warm and cold weather. The colder cycles are referred to as glacial periods and the warmer cycles are referred to as interglacial periods. These periods occur on intervals of 40,000 and 100,000 years. During these cycles ice sheets and glaciers advance and retreat with respect to the climatic conditions. The last glacial period, the Wisconsin Glaciation, ended approximately 11,000 years ago. The deglaciation of ice sheets and glaciers, which happens when we enter a interglacial warming period, are important because they have an immense impact on the land structure and vegetation throughout our continent, as well as the rest of the world. The deglaciation of the Wisconsin Glacier caused the formation of the Great Lakes as well as Niagara Falls in New York. This melting of ice sheets also causes sea levels to rise which covers landforms. The water submerges bridges and passageways between continents that were used by animals which migrated from continent to continent. This prevents certain species of mammals and plants from returning back to their native land, which drastically changes the vegetation and habitat of certain areas. This paper will look at proposed factors that caused previous ice ages and glaciation periods: atmospheric composition, Milankovitch cycles (Earth‘s orbit around the sun), the movement of tectonic plates and changing continental positions.
Our Earth’s atmosphere is made up of such gases as nitrogen, oxygen, methane and carbon dioxide. The purpose of our atmosphere is to protect...