Jurassic: The Dinosaur Era

Dinosaurs, birds and rodents. Crumbling masses and inland seas. Whales, sharks and red plankton. Forests of ferns, cycads and conifers. Tropical, humid, warm breezes. This was the Jurassic. The Jurassic is the period or the system via the era Mesozoic which is also known as Age of Reptiles. The early Jurassic is marked by a mass extinction of species, the extinction of Triassic-Jurassic.

Mesozoic geological era consists of three geological periods, Triassic, Jurassic and Cretaceous. The Triassic period, approximately 248 to 206 million years ago, paved the way for the reign of the dinosaurs on earth and the formation of the giant continent called Pangea.

The Jurassic period is the second of three geological period of the Mesozoic Era and extends from about 199 million years ago until 145 million years ago. This period is characterized by the hegemony of the big dinosaurs and also because it was a period of profound change in terms of changes in the arrangement of continents. As with most geological eras, the exact dates of beginning and end of this period, as in other systems, are conventional, according to certain criteria set for dating, so an error of magnitude is supported by thousands or millions of years.

The name comes from sedimentary Jurassic carbonate formations in the European region of Jura, in the Alps. The mountains are between France and Switzerland.

The most spectacular geographical development was that the Mesozoic Pangea was fragmented and most of this process took place during the Jurassic period. At the end of the Jurassic period, Pangaea supercontinent split into two parts with Laurasia in the north and Gondwana in the south. The eastern part, Antarctica, Madagascar, India and Australia was divided into West Africa and South America.

The most spectacular geographical development of the Mesozoic Era was the fragmentation of Pangea, a process of rifting that began in the region of Tethys, following the old Variscan suture. The Tethys Ocean rose forming a narrow and deep ocean arm that separated Europe from Africa. The rift spread towards the north and south finally beginning to separate South America and Africa. Pangea eventually led to the northern supercontinent Laurasia and the southern supercontinent of Gondwana; the Gulf of Mexico opened the new rift between North America and what is now the Yucatan Peninsula of Mexico.

The rift that formed the Atlantic had another important consequence, the extension produced normal faults between Africa and the northern continents and areas affected by such failures sank, so that the water coming periodically from the Tethys Ocean began to evaporate. These evaporites are now located on both sides of the Atlantic: Spain, Morocco, Newfoundland, etc. During the Middle and Upper Jurassic rift arm moved between North and South America, giving rise to the Gulf of Mexico; another led to the opening of the Bay of Biscay. The Atlantic Ocean north was relatively narrow, and the South Atlantic Ocean was not formed until the Cretaceous, when Gondwana itself broke up.

There was also the great oscillations in sea level. During this period there was a large rise in sea level that caused the flooding of large areas of North America and Europe. During the beginning of the Jurassic period weather conditions they were subjected to sudden changes and the presence of carbon dioxide reached a record high.

Geological records in Western Europe are many and rich, which indicate the presence of shallow tropical seas, most of the continent was submerged for long periods. In contrast, sites Jurassic in North America are among the poorest of the Mesozoic in the continent with very few outcrops . Although epicontinental sea, the Sundance Sea has left marine deposits in North America, the majority of sediments in this area are of continental origin. There are also Jurassic outcrops in Russia, India, South America, Japan, Australasia, Maghreb, Arabian Peninsula, etc.

The first of several batholiths mass is set up along the west coast of North America as the orogeny is very active along the coast. The weather remained warm during this period, but due to the fragmentation of Pangea, this affected the Ocean temperatures, which dropped a little, and besides, the weather became quite wetter. These new environmental conditions favored the development of extensive jungles and conifer forests accompanied by different kinds of ferns and palms.

On land, the dinosaurs were making their mark, literally. The Jurassic age was dominated entirely by dinosaurs, along with the rapid diversification of huge herbivorous sauropods and adaptation to new methods of hunting for some carnivores like Allosaurus. The herbivorous sauropod Brachiosaurus reached 16 meters high, was about 26 meters long and weighed more than 80 tons.

The Diplodocus, another sauropod, measured about 27 meters. The magnitude of these dinosaurs may have dissuaded the Allosaurus, a large, carnivorous dinosaur that walked on two powerful legs, attacking them. But the Allosaurus and other light footed carnivores, such as coelurosaurian, could have come out occasionally successful. Other dams could be huge armored Stegosaurus.

Although conifers remained the dominant trees there were also present terrestrial plants like mosses, horsetails and ferns. Ponytails were the favorite food of herbivorous dinosaurs and since this plant had underground stems, could regrow without experiencing extinction.

During this period also arise the first small birds, but it was the large reptiles Pterosaurs who had control of the Jurassic skies. Later, pterosaurs led to the Pterodactyloids, another group of flying reptiles that rapidly diversified in Africa and northern Europe. Also it arises during the Jurassic one of the first flying dinosaurs, Archaeopteryx, which probably would result in birds.

Jurassic waterways was dominated by fish and aquatic reptiles, among which ichthyosaurs and a new group of large aquatic reptiles long-necked plesiosaurs. Meanwhile, insects such as beetles and cicadélicos were plentiful and many early mammals arose around knowing that the species would dominate the Earth when dinosaurs disappeared in the late Cretaceous.