The supercontinent of Pangea, covering about one quarter of the world’s surface, had persisted for millions of years and continued intact throughout most of the Triassic, but by the latter portion of the period, tectonic forces at last had their way and Pangea began to fracture.
The first phase of deconstruction involved the sundering of the eastern
landmasses allowing the influx of waters from the Panthalassic Ocean to flow
westward, creating the Tethys Ocean and flooding many continental margins. After
the Tethys Ocean formed, Pangea continued to tear apart as the second phase of
dismantling produced two large groups of continents:
As these two continental groups split from one another, a deep rift appeared
along the eastern borders of what would become the North American continent.
This great trench, called the Tethys Seaway, separated North America from Europe
and Africa and would eventually form the Atlantic Ocean. Other geological
changes included the formation of mountains (in China, Japan and along the
western coastlands of North and South America) which in turn prevented the
inflow of moist air from the oceans, further intensifying the arid environments
in the continental interiors.
While Pangea was one land mass, the ocean circulation patterns had not varied much, resulting in a fairly stable climate. (The configuration of the continents has a dramatic effect upon the ocean circulation current, and therefore, the climate.) When Pangea began to break apart, the climate began to slowly moderate, but it wouldn’t be until the Jurassic Period that most of these climatic changes would be fully realized.