The Basin and Range topography develops over a few million years as fault lines move gradually, or more abruptly during tens of thousands of earthquakes. The colder upper crust cracks and breaks along faults (l More
As the plate stretches and thins, the underlying asthenosphere flows upward and expands like a hot-air balloon, lifting the region to higher elevations. The continental crust breaks along faults, forming long m More
750 Million Years Ago—Old Continent Rips Apart. The long mountain ranges and rift valleys were similar to those forming today in East Africa and the Basin and Range Province.
Plate Rips Apart—As the plate stretches and thins, the underlying asthenosphere flows upward and expands like a hot-air balloon, lifting the region to higher elevations; The continental crust breaks along fault More
500 Million Years Ago—Iapetus Ocean Opens. Continental blocks destined to become North America and Gondwanaland drift apart. The eastern edge of ancient North America developed into a passive continental margin More
Rift valleys formed as the thick continental crust (orange) ripped apart and thined. A narrow basin, with thin oceanic crust (black), developed as the two continental fragments split apart.