Paleogeography
Everybody knows about dinosaurs, right? And thanks to the Jurassic Park series of movies, we all know the dinosaurs lived during the Jurassic Period. But what else is noteworthy about this geologic period? I'll try to uncover something other than various dinosaurs to study.
However, I am just as fascinated with dinosaurs as any little kid, so I'll spend some time studying some of our favorites while I'm at it.
The Jurassic Period started 201.3 million years ago and ended approximately 145 million years ago. There was, as seems so common with these geological periods, an extinction event at the dividing point between the Triassic and Jurassic Periods.
The Triassic/Jurassic extinction event seemed to be caused by the Central Atlantic Magmatic Province, which, as best I can figure out, means a lot of magma and lava was moving around in the areas currently known as northwestern Africa, southwestern Europe, southeastern North America and Northeastern South America.
The articles I read seemed to indicate that this was not just a matter of volcanic activity, that some of it could have been caused by the action of diverging plate tectonics. We are aware of the Atlantic rift, where two tectonic plates are moving away from each, allowing a large volume of magma to flow, but this is not considered a volcano. This magma movement began about 201 million years ago, and continued for about 600,000 years. It was the largest activity of this type known to man, covering roughly 11 million km2.
By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The rifting between North America and Africa was the first to happen, in conjunction with the Central Atlantic Magmatic Province
By the beginning of the Jurassic, there was flooding in most parts of central and western Europe, transforming it into an archipelago of islands surrounded by shallow sea. Beginning in the Early Jurassic, the proto-Atlantic was expanded by the "Viking Corridor" (or Transcontinental Laurasian Seaway) which stretched between the Baltic Shield and Greenland, and was several hundred kilometers wide. All during the Jurassic, the North Atlantic Ocean remained relatively narrow, while the South Atlantic did not open until later.
At the beginning of the Jurassic, North and South America remained connected, but at some point, they rifted apart to form the Caribbean Seaway, which connected the north Atlantic Ocean with what is now called the Pacific Ocean, although it was much larger back then, taking up over half the globe and was called the Panthalass Ocean.
About 183 million year ago, another magmatic event started, the Karoo-Ferrar event, this one in South Africa and Antarctica. This triggered another extinction event by causing widespread oceanic anoxia, ocean acidification and elevated temperatures. I am uncertain if these types of conditions were responsible for the Triassic/Jurassic extinction event.
Madagascar and Antarctica rifted away from Africa in association with the eruption of the Karoo-Ferrar large igneous provinces, which opened the western Indian Ocean and began the fragmentation of Gondwana.
During the Middle to Late Jurassic, the Sundance Seaway, a shallow inland sea, covered much of northwest North America.
The sea level rose and fell many times during the Jurassic, peaking at one point as high as 140 meters (462 feet) above the present level.
Wow! So much happening! And that's just the geography! This makes me wonder what else was going on!
https://en.wikipedia.org/wiki/Jurassic
https://en.wikipedia.org/wiki/Central_Atlantic_magmatic_province
https://en.wikipedia.org/wiki/Large_igneous_province
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