Hadean ("Hades-like") Era. This era began with the formation of the earth from dust and gas orbiting the Sun about 4.6 billion years ago. During this era the surface of the Earth was like popular visions about Hades: oceans of liquid rock, boiling sulfur, and impact craters everywhere, meanwhile, during, for example, the Cretaceous period, Earth's land assembled essentially into two continents, Laurasia in the north and Gondwana in the south. These were almost completely separated by the equatorial Tethys seaway, and the various segments of Laurasia and Gondwana had already started to rift apart, and there were oceans of seawater, teeming with life such as Mosasaurs and Ammonites. During the Cretaceous period, the land was hospitable and warm enough to support large numbers of lifeforms, including the dinosaurs.
