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Navštivte Krétu a obdivujte její geologii (Brief Cretan geology)

19.05.2012  |  23× přečteno      vytisknout článek 

Navštivte Krétu a obdivujte její geologii (Brief Cretan geology)

Cretan geology


Crete has not always been as we know it today

As you lie on the sandy beach lulled by the waves, or as you rest in the armchair of your living room, it is hard to imagine that in reality you are surfing. Yes, indeed, you are surfing! To be precise you are "surfing geologically". You are on top of a gigantic "geologic swell" that moves slowly, very slowly, tremendously slowly, but it moves. With it it carries life since it first appeared.

Geologists have estimated that this swell (namely the Earth) started out some 4.5 billion years ago, that is, long before life appeared on the planet.

Then it was a fierce fiery swell covered by thick clouds of nitrogen and helium. Gradually it cooled off, forming lands here and seas there, but until it cooled off for good, there was mayhem. On the very spot of the planet that you are now (or will be soon) sunbathing, there was a deep sea at the time of creation. 25 million years ago

at the beginning of the Miocene epoch, an incredibly powerful tectonic upheaval lifted the bottom of the sea to the surface and, thus, was born - literally from the waves - Aegeis Land, although no human was then available to call it by that name. What was then available included huge elephants, deer, hippopotami, cave dwelling bears and various other beasts roaming undisturbed wherever they pleased. This Aegeis Land was not flat but full of jagged ranges and high peaks. The mountains of Crete were so formed (albeit not in the present shape) 25 million years ago.

Not very deep under the surface of the Earth, the unstable rocks (known as tectonic plates) were in motion causing tremendous uplift and subsidence on the fragile crust. During such a geologic upheaval 12 million years ago, a large part of Aegeis Land sunk and the sea covered everything but the highest peaks. At that very distant era only four mountainous masses must have stuck out of the waters as separate islands, in the area where later Crete managed to float.

The natural see-saw continued for a long time until about 10000 BC. In the course of these hundreds of slow millennia, called Pleistocene epoch by geologists, severe climatic fluctuations created five Ice Ages. Ice, of course, in the form of glaciers, is nothing more than frozen water and it was formed by immense amounts of water borrowed from the sea. Consequently, in each Ice Age, the level of the sea would retreat by 100 to 200 metres! As a result, the four peaks-islands of Crete were joined together and in turn they joined the coast of Peloponnese. Next the ice would melt and everything would be flooded again. After the last ice age (just 12,000 years ago) and the successive ups and downs of sea waters, Crete found peace at last; woods covered the earth, cool water sources sprang out everywhere, a mini paradise was created ready to welcome the first humans.

It seems that humans were not late in coming to the island. Unfortunately, the science of palaeontology is not particularly advanced in Greece and, so, we know very little about the Palaeolithic inhabitants of Crete. Their oldest confirmed traces date from 10000 BC approximately. After that, circa 2600 BC, an Indo-European people came from the east and mixed with the natives to form in tandem the famous Minoan civilisation. Afterwards, circa 1400 BC, Greek tribes came to settle here such as the Achaeans, to be followed shortly by the Dorians. Then, for short or long periods came here and settled Byzantines, Arabs, Genoans, Venetians, Turks, Germans, every man Jack. And now you, lying on the beach, are travelling carefree on top of the swell. Bon voyage and be careful.

Maps on:

http://www.sed.manchester.ac.uk/geography/undergraduate/fieldwork/crete/maps/geology.htm

ZDROJ:www.alpha-omegaonline.com


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