Pangaea existed for million years, and during that time period several animals flourished, including the Traversodontidae , a family of plant-eating animals that includes the ancestors of mammals. During the Permian period , insects such as beetles and dragonflies flourished.
But the existence of Pangaea overlapped with the worst mass extinction in history, the Permian-Triassic P-TR extinction event. Also called the Great Dying, it occurred around million years ago and caused most species on Earth to go extinct. The early Triassic period saw the rise of archosaurs, a group of animals that eventually gave rise to crocodiles and birds, and a plethora of reptiles.
And about million years ago some of the earliest dinosaurs emerged on Pangaea, including theropods, largely carnivorous dinosaurs that mostly had air-filled bones and feathers similar to birds. The current configuration of continents is unlikely to be the last. Supercontinents have formed several times in Earth's history, only to be split off into new continents. Right now for instance, Australia is inching toward Asia, and the eastern portion of Africa is slowly peeling off from the rest of the continent.
Geologists have noticed that there is a quasi-regular cycle in which supercontinents form and break up every to million years, but exactly why is a mystery, Murphy said. But most scientists believe that the supercontinent cycle is largely driven by circulation dynamics in the mantle, according to a article in the Journal of Geodynamics. Beyond that, the details get fuzzy. While the heat formed in the mantle likely comes from the radioactive decay of unstable elements, such as uranium, scientists don't agree on whether there are mini-pockets of heat flow within the mantle, or if the entire shell is one big heat conveyor belt, Murphy said.
Even though we may think of Pangaea as made up of the seven continents today, it was a unique continent at the time it existed and its existence didn't depend on modern continents. Gondwanaland is the name of another clumping of continents, one that was large, but smaller than Pangaea and occurring at a different time - at the end of the Mesozoic. The large northern continent is called Laurasia and the southern continent is called Gondwanaland.
Laurasia and Gondwanaland were separated by an ocean called Tethys that no longer exists today. These plates are in constant motion causing earthquakes, mountain building, volcanism, the production of "new" crust and the destruction of "old" crust.
The following cards will teach you more about the Earth's plates. The Earth's crust is broken into many pieces. These pieces are called plates. There are twelve main plates on the Earth's surface. The red lines on this map of the world represent the largest plate boundaries. A plate boundary occurs where two plates come together. There are three kinds of plate boundaries:.
Convergent boundary -where two plates collide to form mountains or a subduction zone. Divergent boundary -where two plates are moving in opposite directions as in a mid-ocean ridge. Transform boundary -where two plates are sliding past each other as in the San Andreas fault of California. The Earth's plates are in constant, but very, very slow motion.
This does not seem like much, but over millions of years it adds up to great distances of movement.
The Continental Drift Theory states that the continents have moved and are still moving today. In Alfred Wegener introduced this theory, but he did not fully understand what caused the plates to move. A theory is an explanation of a scientific process that has been successfully tested by many different methods. The motion of the Earth's plates help scientists to understand why earthquakes, volcanoes, and mountain building occur. You will learn more about why the plates are moving in the next lesson, "How Plates Move".
Scientists believe these plates have been moving for millions of years. In fact, millions years ago the Earth's seven continents were all grouped together into a supercontinent called Pangea.
Just before the days of the dinosaurs the Earth's continents were all connected into one huge landmass called Pangaea. The two main constraints are geography and climate. Turning to climate, the frequency of rainfall along lines of latitude directly influenced where animals lived, the scientists write in a paper published this week in the online early edition of the Proceedings of the National Academy of Sciences.
In the tropical zone where the mammal-relative traversodont cynodonts lived, monsoon-like rains fell twice a year. But farther north on Pangaea, in the temperate regions where the procolophonids predominated, major rains occurred only once a year.
It was the difference in the precipitation, the researchers conclude, that sorted the mammals' range from that of the reptiles. On Pangaea, the mammals needed a water-rich area, so the availability of water played a decisive role in determining where they lived. In water-limited areas, "the reptiles had a competitive advantage over mammals," Whiteside said. She thinks the reptiles didn't migrate into the equatorial regions because they already had found their niche.
The researchers compiled a climate record for Pangaea during the late Triassic period, from million years ago to million years ago, using samples collected from lakes and ancient rift basins stretching from modern-day Georgia to Nova Scotia. Pangaea was a hothouse then: Temperatures were about 20 degrees Celsius hotter in the summer, and atmospheric carbon dioxide was five to 20 times greater than today.
Yet there were regional differences, including rainfall amounts. The researchers base the rainfall gap on variations in Earth's precession, or the wobble on its axis, coupled with the eccentricity cycle, based on Earth's orbital position to the sun.
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