Introduction to Triassic and Early Jurassic Periods
Dinosaurs had not arrived as the Permian Period ended and the Triassic began. The earth's land and climate were changing, the ancestors of the dinosaurs were evolving, and many plants and animals were becoming extinct. Because these events took place, dinosaurs became rulers of the earth by the Jurassic Period.
Canadian Museum of Nature
At the beginning of the Triassic Period, all land was joined as a single large mass called Pangaea. It stretched nearly pole to pole. The only block of land not joined to Pangaea was southern China and southeast Asia, which collided with the Chinese mainland before the Late Triassic. Throughout the Triassic, Pangaea slowly moved north and turned clockwise. By the Middle Triassic, the continent was a crescent-shaped mass facing east and centered on the equator. The eastern side of Pangaea surrounded a large body of water, the Tethys Sea, which joined a single global ocean.
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Large land masses are more sensitive than oceans to heating and cooling. During a hemisphere's summer, a large land mass warms the hemisphere. It then becomes the center of cooling during the hemisphere's winter. This produces air pressure changes, which result in strong seasons. Although scientists disagree about the exact climate, it seems the Triassic started out cool and dry and became warmer, with rainy summers and drier winters. This became a monsoon weather pattern, as in southeast Asia today.
This weather pattern affected the soil and land. Vertisols are fossil soils produced by a wet season followed by a dry season. This soil is found in Triassic formations. Red beds are also widespread in Triassic formations. Red beds get their color when iron in the soil oxidizes (rusts) because of warm, somewhat dry weather.Triassic plants included ferns, conifers, and cycads. These plants would have needed warm, moist weather to survive. Throughout the Triassic, some plants were becoming extinct and others were evolving. The Late Triassic plant Sanmiguelia may be the ancestor of flowering plants, though it did not become established until the Early Cretaceous.