The evolution of man has gone through great difficulties throughout history. One of these obstacles has been the glaciations and the impact they have had on the global temperature of the earth, which has hindered the faster development of man. There is talk of several ice ages, some colder than others, but generally affecting planet earth and human beings . Glaciation definition geography
What is the glaciation?
An ice age is defined as an extended period in which the global temperature drops extremely causing the expansion of continental ice in the polar caps and glaciers . The glaciations have a subdivision called glacial periods, and Würm is the last one to the present.
Over millions of years, from prehistory to the present , planet Earth has undergone changes to be what we know today. Previously they occurred naturally, today many of the environmental and structural changes of our planet are produced by human beings and most of all by the pollution that is generated, affecting the natural course of the balance it has. Glaciation definition geography
Based on the definition given by glaciology, the term glaciation refers to a period where there are ice caps in both the northern and southern hemispheres . This means that according to this definition, we are still facing an ice age because there are still polar ice caps in Greenland and Antarctica.
Ice ages throughout history
In the past there have been at least four large ice ages. These periods aside, the Earth was apparently always ice-free even at the highest latitudes. The Huronian Glaciation is the oldest hypothetical glaciation , taking place at the beginning of the Proterozoic eon 2700 and 2300 million years ago.
The oldest well-documented and strongest glaciation in the last billion years took place 850 million years ago and ended 630 million years ago , probably producing a global glaciation. It ended very quickly while the water vapor returned to the atmosphere increasing the greenhouse effect caused, because the carbon dioxide emanated by the volcanoes accumulated, this because the icy seas did not have the capacity to absorb this gas. Glaciation definition geography
Andeana-Saharan was a minor glaciation that occurred between 460 and 430 million years in the Upper Ordovician and Silurian , and had intervals with fairly extensive polar caps between about 350 and 260 million years ago, during the Carboniferous and Cisuralian that are related with the Karoo glaciation. Glaciation definition geography
The glaciation that exists today, began 40 million years ago with the expansion of one of the ice sheets in Antarctica . This intensified at the end of the Pliocene, about 3 million years ago, with the ice sheets of the northern hemisphere spreading and continued during the Pleistocene.
Since this time, the planet has experienced cycles of glaciation with the advance and retreat of the ice sheets for thousands of years. The most recent glacial period ended about ten thousand years ago, for this reason depending on the author who explains it, it could be said that we are in an interglacial period, although other positions assure that we are in a postglacial era. Glaciation definition geography
Effects and consequences of glaciations
- Geological : Geological effects are found in various forms, one of which is weathered rocks, glacial valleys, mud rocks, drumlins, glacial moraines, valley trains, erratic blocks, alluvial plains fractures, fjords on the coasts and lakes on the plains. This means that the climatic conditions typical of an ice age produce the appearance of the aforementioned physiognomies. With each glaciation some geological evidence is distorted and eliminated, making its interpretation difficult.
- Chemicals : Chemical effects are mainly proportional variations of isotopes in sedimentary rocks, ocean sedimentary cores, and for more recent periods of glaciation, ice cores. This is because water with heavier isotopes evaporates at higher temperatures and the amount is reduced when conditions are colder; Thanks to these processes, a thermal record was created. However, the tests could be corrupted by other aspects that change the proportions of the isotopes. One of these events that could adulterate the results would be a mass extinction that increases the proportions of light isotopes in sedimentation and in ice because these biological processes tend to prefer these two. Glaciation definition geography
- Paleontological: paleontological effects are based on changes in the geographical distribution of fossils. In the course of ice ages, living things that have adapted to the cold migrate to lower latitudes and living things that have a preference for warm climates live in equatorial areas or become extinct. This gives rise to the appearance of glacial refuges and return biogeographic movements. These clues are also difficult to interpret because sediment sequences are needed that demonstrate a long period, different latitudes that are able to be easily correlated. Primitive organisms present over long periods and with sufficiently homogeneous characteristics to be attributed to the same taxon and also their ideal climate to be known are also necessary.