Stromatolites

Phanerozoic History

Mesozoic era
Early in the Mesozoic much of the land was above sea level
By the middle Mesozoic, seas invaded western North America
Pangaea began to break apart and the westward-moving North American plate began to override the Pacific plate

Mesozoic era
Pangaea began to break apart and the westward-moving North American plate began to override the Pacific plate
Resulted in crustal deformation along the entire western margin of North America
Formed the Sierra Nevada and Rocky Mountains

Cenozoic era
Much of North America was above sea level throughout the Cenozoic
Eastern and western margins of the continent experienced markedly contrasting events
Atlantic and Gulf coastal regions, removed from active plate boundaries, were tectonically stable

Cenozoic era
Much of North America was above sea level throughout the Cenozoic
In the West, the Laramide Orogeny (Rocky Mountains) was ending, the Basin and Range Province was forming, and volcanic activity was extensive

Earth’s First Life

Prokaryotes
First known organisms
Single-celled bacteria
Lacked a nucleus

Cynobacteria
One group of prokaryotes
Used solar energy to synthesize organic compounds, thus producing their own food
Fossil evidence of these bacteria include layered mounds called stromatolites