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5.2. Earth, a changing planet

Earth, a changing planet

The Earth, since its formation, has been in constant flux and will continue to change in the future. We can see these changes when an earthquake occurs, when a volcano erupts or when rain contributes to erode and wash materials from a mountain. But we humans also participate in the change of our planet when we alter its dynamics by building dams, roads, cities, etc.

In addition to these rapid and more obvious changes, there are others that manifest themselves more slowly, such as the movement of lithospheric plates that separate the continents or generate mountain ranges, or the retreat of glaciers.

Some of these changes that show that the Earth is a changing planet are:

Climate changes

Changes in climate have also occurred throughout Earth's history. Not only current climate change caused by environmental pollution, but also other naturally produced climate changes.

In the climate, the warm or greenhouse stages alternate with other cold periods or glaciations. During glaciations, ice covers a large part of continents and oceans. For example, during the last ice age, ice covered 30% of the emerged surface of the Earth and was about 4000 meters thick.

For about 10,000 years we have been in an interglacial period.

You can tell what the climate was like in other times by the rocks that were formed:

Changes in the atmosphere

The main change that has occurred is that the early atmosphere lacked oxygen and had more carbon dioxide than the atmosphere today. The ozone layer (O3), formed by oxygen, did not exist either , which currently protects the Earth from ultraviolet radiation.

The causes of these changes were photosynthetic organisms, which favored the appearance of oxygen and the decrease of carbon dioxide. In addition, with the appearance of the ozone layer, many aquatic organisms were able to colonize the terrestrial environment.

Changes in biodiversity

Changes in biodiversity are also evident. We find fossilized remains of living beings that no longer exist today and we even see some species become extinct.

There are times, when environmental conditions favor it, in which there is a rapid increase in the number of species and others, for some reason, in which species are suddenly extinct.

Earth, a changing planet in other courses

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