In many locations, Alexander terrane limestone rests on top of conglomerate made up of beach boulders. During these plate collisions in the arctic, the Brooks was for scores of thousands of years a rim of violent active volcanoes.

Show us your rocks! In the Mesozoic, North America separated from the supercontinent Pangea which had formed in the late Paleozoic. Intense volcanism built up Alaska's mountains until a slowing of eruptions in the late Cretaceous around 80 million years ago. Most, however, agree that the warming from the peak of the ice age released the waters from the ice cap back to the oceans sufficiently to cause the oceans to rise and cover Beringia some 23,000 years ago (plus or minus 3000 years). Thrust faults and the Chatham Strait Fault separate the small Taku terrane from neighboring terranes. "This is blood for blood and by the gallon. The Pacific Ocean then extended from somewhere near the present location of Prince Rupert in Canada to the arctic islands. So for a relatively short time (in geologic terms), Asia and North America were connected by the Beringia land bridge.

Various types of agates can be found in gravel pits and river beds at several locations in the Chicken Creek area near the border with the Yukon Territory. In 1896, the Klondike Gold Rush attracted prospectors and others from all over the world. Geology has named this land mass, that does not exist today, Beringia.

1 Saves. Learn more about this land that is sculpted by ice. Immense tectonic forces wrinkle and crumple terranes to form the Alaska range that looks like a spiny backbone to the park.