How Was Arches National Park Formed - Arches national monument— established april 12, 1929. Web as tectonic forces pushed and pulled what was to become north america, the ancestral rocky mountains rose. Web the entire region began to rise 15 million years ago, and increasing erosion caused removal of the sedimentary rocks above.
Web the entire region began to rise 15 million years ago, and increasing erosion caused removal of the sedimentary rocks above. Web as tectonic forces pushed and pulled what was to become north america, the ancestral rocky mountains rose. Arches national monument— established april 12, 1929.