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Southeast Alaska - A Sculpted Wilderness

Devil's Thumb peak.

At one time all of the land on Earth was joined together in one super continent, known as Pangea. It broke apart dividing the surface of the Earth into six to eight continental plates. The future North America wandering dramatically with other continents, sometimes served as the North Pole, other times it stood at the equator with a tropical climate. Over the millennia these plates moved to positions resembling their current configuration.

Alaska was flat, mountainless and treeless, lying just above sea level. Temperatures ranged from 120° below zero to 120° above. Very little grew on the land except for mosses, ferns, and low shrubs. Frequently enormous slabs of earth, some the size of Kentucky, would creep north in the Pacific and slam into the Alaskan coast causing a sudden uprising of mountains and enlarging the landscape. Eight to ten of these huge pieces shaped Alaska and approximately 70 million years ago present day Alaska took shape.

Continental plates crashed the north coast, creating the Brooks Range. The Pacific Plate slammed its way into the North American Plate, undermining it and pushing up the terrain to form the Alaska Range and Coast Range. It's still pushing at the rate of two inches a year. Stresses caused by these movements create dramatic results. Certain areas, such as the Aleutian Islands, are well known for their volcanoes and earthquakes.

A beautiful Alaskan peak.

From time to time, during the last billion years great sheets of ice would expand from the North Pole growing thicker and covering vast areas, reaching as far south as New York. These ice sheets were continental size glaciers like those in Antarctica and Greenland. These continental ice sheets, in places more than a mile thick, would eventually recede and advance again over long cycles. From ice core samples in Greenland we know that about two million years ago a series of six relatively brief ice ages arrived. These ice core samples also indicate that these cyclical ice ages were triggered by volcanic activity and rotational cycles of the Earth. The last of these cycles ended only 14,000 years ago, the end of the Great Ice Age.

In Alaska during periods when the ice advanced, ice sheets covered the Brooks Range, Southeast Alaska, South Central Alaska, and the Aleutians. However, Central Alaska remained ice free during these icy periods since the mountains near the coast would rob moisture from the oceans before it could move inland. At maximum only about thirty percent of Alaska was covered by ice.

Where did this ice come from? The oceans. Over thousands of years winds would carry moisture on shore deposited as snow. So much, in fact, to drop the level of the ocean by 300 feet. Land areas previously separated by water were now joined. Australia was attached to Antarctica and England to Europe. But the most spectacular was the joining of two gigantic continents, Asia and North America--in the area of the Bering Sea. The exposed area, known commonly as the Bering Land Bridge, was so large that it was also given the name of a new continent--Beringia.

Glaciers have carved the many fjords of Southeast Alaska's coastline.

About 35,000 years ago Asian animals such as mastodons, woolly mammoths, deer, caribou, moose, sheep, bison, and horses crossed the Bering Land Bridge. What attracted them to North America? The environment adjacent to glaciers is special. Glacial erosion unleashes new supplies of mineral nutrients and the plants that do exist near glaciers are mineral-rich and well-watered, the perfect diet for mammalian herbivores. This abundance of food allowed for gigantic sizes, like the mastodons and mammoths and flamboyant social garb, like antlers, manes, and tusks. In turn these herbivores attracted carnivores new to North America--Saber-toothed tigers, bears, and wolves. This new diversity of life transformed Alaska into the Serengeti of North America.

About 12,000 years ago, man first crossed the Bering Land Bridge. As the Ice Age was ending, Alaska became wetter in summers and experienced deeper snows in winter. The vegetation changed from primarily grasses to today's forests and shrub tundra. These changes caused extinction of mammoths, mastodons, and horses, while caribou and moose thrived.