Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60Wyoming’s tectonic past 9 In the Earth’s ancient past,Wyoming was part of Laurentia, a precursor to the North American continent. In the early Mesozoic era, the part of North America that would become Wyoming was close to the Earth’s equator. 1. 252–245 mya (during the Early Triassiac period) In the late Cretaceous period, 86–72 mya, Wyoming was almost completely covered with water, except where the Rocky Mountains were beginning to rise in the western part of the state. 3. 86–72 mya (during the Late Cretaceous period) At times the North American continent collided with and joined other continental plates and then millions of years later drifted away from them. About 175–166 million years ago (mya), North America began to separate from South America and Africa. 2. 174–166 mya (during the Middle Jurassic period) By the early Cenozoic era, 66–59 mya, the last of the ancient seas over Wyoming had dried up. As the Earth’s crust moved and caused mountains to rise, it also caused the basins between mountains to sink, in some places as much as 30,000 ft. 4. 66–59 mya (during the Paleocene period) Data Go Interactive