Ice Ages Glaciations are long lasting periods during which temperatures around the entire earth down considerably resulting in the expansion of the continental ice of the polar ice caps and glaciers. "In periods of glaciation are more severe conditions and others a little more temperate glacial and interglacial periods called periods respectively." There have been several periods of glaciation throughout the life of our planet Earth, The Huronian (2400-2100 thousand years), Cryogenic (850-635 ty), the Andean-Saharan Africa (450-420 ty) Karoo (360-260 ty) and Quaternary (2.58 ty-present). Within each of those years of glaciation may have subdivisions depending on the geographical scope and the time of glaciation. The Huronian glaciation glaciation is the oldest known and most lasting. The second glaciation known as Cryogenic was considered the most severe and is believed to date produced more than one SNOWBALL EARTH in the balloon terraque froze completely. It is known as SNOWBALL EARTH to a series of global glaciations where oceans and continents were covered by thick ice sheets reaching temperatures of -50 degrees Celsius. His impact was so strong that he thinks that life was about to disappear from the planet. It is believed that periods of intense cold were obstacles to the evolution of multicellular life. The oldest known embryos appear a million years after completion of the global glaciation. It is assumed that the ice and the cold prevented the emergence of complex life (multicellular organisms). The current causes of ice ages remains a controversial topic, but is thought to be a number of factors which ocacionan this, changes in the Earth's atmosphere, position of continents, Milankovich astronomical cycles, variations in solar activity, volcanism , galactic cosmic radiation,. Changes in the Earth's atmosphere, it is believed that the level of greenhouse gases as well as the reduction of CO2 are the cause of ice ages. If the position of the continents is such that prevents or reduces the arrival of the warm water to the poles Ecuador favoring the formation of ice caps, increasing the albedo of the earth, reducing the absorption of solar radiation, with that cooling the atmosphere, resulting in the growth of ice caps, increasing this still more so the albedo and continuing until the erosion causes a greenhouse effect, this will cause ice ages. Variations in solar activity are causing variations in temperature and this is very likely to be another cause of ice ages. Today, glaciers cover 10% of Earth's surface. At the time of the ice ages, this percentage increased to 30%. The land areas located in areas occupied glaciers in the glacial eras have landforms and associated sediments. Glaciers cause deviations from streams in existing drainage systems and thereby have indirect effect on the landscape.
Orography:
The last glacial period ended 9000 years, yet the effect is visible in the landscapes were the movements of large masses of ice. "The weight of the ice sheets deformed the Earth's crust and mantle; when the ice melted, the crust was raised by isostasy. Due to the high viscosity of the Earth, the flow of mantle rocks is very slow, and this process occurred at a rate of one centimeter per year. It is recognized that this 'refloat' bark involves earthworks, changes in sea level in the Earth's magnetic field, inducing earthquakes and even changes in the Earth's rotation. " Large volumes of water that froze at high latitudes during the ice formed on bridges where the emigration of species resulting in the current evolutionary changes in biodiversity are allowed. The melting of glaciers originated the creation of saline lakes.
"Each glacial period is subject to positive feedback which makes it more severe and negative feedback which mitigates the effects and eventually restore the balance."