Eesti Loodusmuuseum/Näitus/Müstiline ürgmeri/ENG: erinevus redaktsioonide vahel
Eemaldatud sisu Lisatud sisu
Kruusamägi (arutelu | kaastöö) Resümee puudub |
Kruusamägi (arutelu | kaastöö) Resümee puudub |
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61. rida:
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=== THE SILURIAN ===
;THE TERRITORY OF ESTONIA ON THE EQUATOR
During the Silurian, three separate continents – Baltica, Avalonia and Laurentia – rapidly shifted towards one another. At the end of the period, a triple collision of these continents took place on the equator, resulting in the formation of a new continent – Laurussia. The territory of Estonia, which had so far remained part of the Baltica palaeocontinent, now got positioned on the plain in front of the Caledonide Mountains, which had started to rise along the collision zone between Laurentia and Baltica. The shallow sea with changing sea level that covered Europe 400 million years ago sometimes covered Estonian territory or left it as dry land.
;THE FIRST BONY FISH
During the Silurian, the first bony fish appeared in the seas, while the first mosslike plants and arthropods appeared on land. The tropical sea covering the area of Estonia was inhabited by corals, sea lilies, sponges, brachiopods, moss animals, graptolites, various bivalves and other molluscs, as well as predatory nautiloids. The now extinct stromatoporoid sponges reached a particularly wide distribution. Some completely new evolutionary branches also arose. Of these, these waters hosted predatory sea scorpions and representatives of several fish groups.
''By the end of the Silurian, the global average temperature was up to ten degrees higher than today.''
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Eurypterus Smithsonian.jpg| †''Eurypterus''. Eurypterids, or sea scorpions, were up to 2.5-metre-long predatory arthropods that have gone extinct by now.
Estonian Museum of Natural History - Nautiloid (coiled).png| Nautiloids. Predatory cephalopods had either straight, curved or spiral shells depending on species.
Estonian Museum of Natural History - Birkenia.png| †''Birkenia robusta''. An extinct up to 10-centimetre-long jawless fish, probably the ancestor of modern lampreys.
Estonian Museum of Natural History - Moss animals.png| Moss animals. Sedentary colonial marine animals that are still widespread today.
Estonian Museum of Natural History - Rugosis.png| †Rugose corals. A now extinct order of solitary or colonial corals that once lived in coastal seas.
Estonian Museum of Natural History - Crinoid.png| Sea lilies. Sea lilies, or crinoids, belong to the phylum of echinoderms and formed extensive thickets in Silurian seas.
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=== THE DEVONIAN ===
;THE PERIOD OF RED SANDS
The map of the Devonian period is dominated by two larger landmasses and a number of smaller continents. The ancient supercontinent Gondwana sprawled over the South Pole, while the nascent Laurussia lay on the equator. The present territory of Estonia was situated in the central part of Laurussia, on the plain in front of the Caledonide Mountains. A hundreds of meters thick layer of reddish sands from the Caledonides was deposited in South Estonia and the adjacent areas during the Devonian.
;FISH-RICH TERRITORY OF ESTONIA
A period of greenhouse climate that had started already several dozen million years earlier, in the Silurian, continued through the Devonian and for further 100 million years on end. An exceptionally rich biota thrived also in the warm tropical seas of the Devonian. Rapid diversification and mass spread of fish took place in the ocean. A peculiar group known as Placoderms became dominant among fish but went extinct by the end of the period. They lived also in the sea that covered part of present-day Estonia and could grow up to two metres in length. Also the first amphibians are known from the Devonian, as are treelike terrestrial plants that grew up to several dozen metres tall.
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Estonian Museum of Natural History - Archaeopteris.png| †''[[:en:w:Archaeopteris|Archaeopteris]]''
Estonian Museum of Natural History - Pseudosporochnus.png|†''[[:en:w:Pseudosporochnus|Pseudosporochnus]]''. Early treelike plants resembled giant ferns and grew 2–10 metres tall.
Estonian Museum of Natural History - Psammolepis Alata.png| †''[[:en:w:Psammolepis alata|Psammolepis alata]]'' (depicted) and †''[[:en:w:Drepanaspis|Drepanaspis]]''. Up to 1.5-metre-long jawless fish that once lived in these waters, resembling modern rays.
Estonian Museum of Natural History - Microbrachius.png| †''[[:en:w:Microbrachius dicki|Microbrachius dicki]]''. The first animals known to have used internal fertilisation to produce offspring.
Estonian Museum of Natural History - Pteraspis.png| †''[[:en:w:Pteraspis|Pteraspis]]''. An extinct jawless fish whose up to 20-centimetre-long front part of the body was covered with a protective armour of bony plates.
Panderichthys BW.jpg| †''[[:en:w:Panderichthys|Panderichthys]]''. This extinct species from the class of lobe-finned fish represents an evolutionary stage between bony fish and early four-legged animals.
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| HAS THE AREA OF ESTONIA BEEN HOME TO DINOSAURS?
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| The Mesozoic was the era of dinosaurs and reptiles. Rocks from this period are absent in Estonia because the area was subject to terrestrial conditions for several hundred million years and no rocks were formed during that time. Besides, a surface rock layer as thick as dozens or hundreds of metres has been eroded away by several continental ice sheets of later periods. The next entry in the fossil record of this area dates from just a few dozen thousand years ago. There is still reason to speculate, however, that various representatives of dinosaurs might have roamed also these neighbourhoods.
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| ''Dinosaur bone finds closest to Estonia originate from Russia, Ukraine and several other locations in Europe''
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=== ICE AGE ===
;THE TERRITORY OF ESTONIA GETS COVERED WITH ICE
The Quaternary is the most recent period in Earth’s history, spanning from about 2.6 million years ago to the present. During the Quaternary, harsh ice ages have alternated with interglacial periods of milder climate. We currently live in an interglacial period following the most recent major glaciation. The world of the Quaternary is familiar to us. The boundaries of continents have been somewhat altered by sea level fluctuations over the last couple of million years but, in general, the positions of continents on the world map are already familiar to us.
''During the latest ice age, the entire territory of Estonia got covered with an about kilometre-thick sheet of ice, which bulldozed huge quantities of loose ground and older rocks out of its way.''
=== THE PRESENT ===
;FORMATION OF THE BALTIC SEA
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