Volcanoes
Volcanoes shape the land in many ways.
Golden Horn is the mountain to the southwest (see photograph). It looks like a volcano, but it isn't. However, about 8.6 million years ago, lava flowed from a crack near its base forming a thick layer of basalt that can be seen at Miles Canyon. There were over a hundred volcanoes active in Alaska through the last glacial age. Many are still active today.
Golden Horn Mountain. Photo: Barb Hogan
Inset: Layers of White River ash, South Canol Road, Yukon. Photo:
Pam Sinclair
Plants and animals cannot survive under volcanic ash.
Erupted ash from these volcanoes periodically blanketed nearby land and regions hundreds of kilometres downwind. Volcanic ash can smother plants, contaminate water and reduce the number of game animals forcing people to move. This happened in the Yukon when Mount Churchill, on the Alaska border, erupted about 1,150 years ago. The White River ash from this eruption can be seen in cut banks along Yukon highways.
Active volcanoes of Alaska, the Yukon and the Russian Federation.
Volcanic eruptions change the climate.
Volcanic eruptions alter the global climate for both short and long periods. Cool temperatures following the 1815 Tambora eruption in Indonesia caused crop failure and famine in North America and Europe. Volcanic dust and gases thrown into the air during this eruption caused temporary cooling. Carbon dioxide released by repeated eruptions over thousands or millions of years can cause long-term global warming.
Eruption of Mount Pinatubo, Phillipines, 1991. For two years following the eruption,
average global temperatures dropped over 0.5C (approximately 1F). Photo:
T. J. Casadevall, U.S. Geological Survey
Can volcanoes trigger both Ice Ages and global warming?