Alaska's past is better understood if one also knows Alaska's geography. This includes Alaska's relationship on the Earth's surface to the rest of the world.
The topography, or shape of the land, is important to historical study. It has determined where people have lived as rugged mountains are beautiful, yet friendly river valley's are more livable. The land is constantly changing. Violent earthquakes, volcanic eruptions, tsunamis, and glaciers cause dramatic changes, but annual break-up of river ice, rain, or daily winds also cause changes in the physical environment.
From the studies of Alaska's volcanoes, earthquakes, and landscapes, some scientists argue that Alaska was created when two continental plates ran into each other. When the plates collided, the two continents merged into one single, much larger continent. Other geologists believe Alaska was pieced together from parts of at least seven plates that collided and fused over a long period of time. However, most geologists think that Alaska was pieced together over long periods of time from small islands carried in from the Pacific Ocean Plate. These geologists agree that Alaska's major features were shaped about 125 million years ago.
Alaska is influenced by the movement of two major plates, the Northward-moving Pacific Oceanic plate that is slipping under the North America continental plate.
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