When snow compacts over a long period of thousands of years, a glacier is created. This ice sheet covers 10% of the planet, has a thickness that varies between one and five kilometers and below it is a land mass. The discipline that studies glaciers and the impact of ice on the earth's relief is glaciology.
The transformative power of ice
By glaciation we understand a period of very long duration in which the Earth's temperature drops significantly and as a result the ice expands, especially in the polar and glacial areas.
The phenomenon of glaciation is produced by the action of three factors. In the first place, the Earth's tilt axis shows a variation over time (as its angle increases, the seasons are more extreme in both hemispheres and thus summers are getting warmer and winters are colder).
Second, the variation in the Earth's orbit around the Sun (every 100,000 years this trajectory presents a series of changes and this circumstance causes the variation in temperature to become more acute in each season).
Finally, an ice age occurs due to the phenomenon of precession or, in other words, the variation of the Earth's axis of rotation. These general causes combine in a certain way and end up creating one type of glaciation or another.
The first evidence of the glacial period appeared in the 19th century
Swiss geologist Louis Agassiz compared the rocky landscape of North America with mountain glaciers in Switzerland and concluded that the North American territory remained covered in ice millions of years ago.
In the 1950s, new evidence appeared on the seabed and revealed that during the archaic stages of the Earth there was an ice age. This information allows us to better understand the geological history of our planet and climate changes.
The scientific evidences that demonstrate the phenomenon of the glaciation are in the valleys with form of U (the valleys with this form indicate that there was abundant ice in the past). According to the majority of studies carried out today, we are in an interglacial period.
The so-called Little Ice Age has been one of the most recent glaciations
Between the XlV and XlX centuries there was a remarkable cooling of temperatures.
There is no absolute certainty about the causes that could explain this phenomenon, but several hypotheses are used: a slight decrease in solar activity, natural changes in the climate and human action.
Fotolia photos: JumalaSika / Camerawithlegs
