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If you like big things, the Trias can be done for you. Dinosaurs have not only evolved to dominate the world, but some have occurred on a geological entity 15 times larger than any modern equivalent. A vast deltaic plain at the edge of the North Ocean covered more than 1% of the Earth's land mass at the time. A new study has explained how it has become the largest plain of its kind in the history of the Earth.
The delta plains may not attract mountain ranges or coral reefs, but they are important for planetary ecology. Regular floods by silt-laden waters make the place where winding rivers meet the sea of exceptional fertility. The flourishing of plants and animals in these places today allows to imagine that many species of dinosaurs first evolved in these regions. More recently, their role as cradles of agriculture and therefore of civilization gives us many reasons to be interested in their development.
Dr. Tore Grane Klausen, of the Norwegian University of Bergen, wanted to know how the plain bordering the Boreal Triassic Ocean (TBO) reached a phenomenal area of 165,000 square kilometers. Near the size of the state of Washington and larger than England and Wales combined, it was fed by a network of rivers that drained as large a surface as the Amazon. In geology, Klausen and his co-authors identify two essential components throughout the plain: a long period of sea level stability and the flatness of the seabed in which its rivers flowed.
Today, the TBO Delta Plain lies under water, between the northern tip of Norway and the island of Svalbard (Spitsbergen). Even though it was above sea level, the area would hardly harbor any more than polar bears, but during the Triassic, its climate resembled that of modern southern Asia.
The area was heavily drilled in the hope of finding oil, but it is much less known than if it were terrestrial. Therefore, the size estimate is a minimum, its limits in some directions not being established.
The modern plains of the delta are less than 10,000 years old. All that existed before was submerged by sea level rise. Until we began damming their rivers, many were expanding, but their growth rate was limited. The largest, at the mouth of the Amazon, is only 10,800 square kilometers.
Other older delta plains have been found beyond those of today, but none correspond to the size of the TBO plain.
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