Natural Phenomena - Part 2

Natural Phenomena - Geothermal Features

Alaska is rich with geothermal features such as volcanoes, fumaroles (steam pots), and hot springs.






Vocanoes

There are approximately 500 active volcanoes in the world; 70 of these are located in Alaska.

Most all of Alaska's volcanoes are located along the 1,500 mile Aleutian Arc that extends westward to Kamchatka and forms the northern part of the Pacific Ring of Fire.

According to the U.S. Geological Survey, the largest eruption on Earth in the 20th Century occurred in Alaska at Novarupta Volcano, near Mount Katmai, in June 1912. The eruption created the Katmai Caldera and the Valley of Ten Thousand Smokes. Volcanic ash, more than from all other historical eruptions in Alaska combined, devastated areas hundreds of miles away.

Alaska's most recent significant eruption was Redoubt, in March 2009. It sent plumes of smoke and ash about 9.5 miles into the sky and caused flight cancellations.














Major eruptions along the Aleutian Arc occur almost every year. However, eruptions in unpopulated areas often go unnoticed by everyone except those who study volcanoes.

Volcanoes also exist beneath the ocean's surface and are called seamounts. About 100 of these extend from the Gulf of Alaska to the Oregon coast.

Fumaroles

A fumarole (Latin fumus, smoke) is an opening in the earth's crust, often in the neighborhood of volcanoes, which emits steam and gases.

The Valley of Ten Thousand Smokes, which was formed during the 1912 eruption of Novarupta in Alaska, provides a classic example of fumaroles. Initially, there were thousands of fumaroles in the cooling ash from the eruption, but over time most of them have become extinct.

Fumaroles escape through Fourpeaked Glacier covering Fourpeaked Volcano in Alaska on September 24, 2006





There are also an estimated four thousand fumaroles within the boundaries of Yellowstone National Park. (JHAWK note: have also seen these in Iceland - another land of volcanoes - and at California's volcanic Mt. Lassen.)

Hot Springs

Hot springs are produced by the emergence of geothermally heated groundwater from the Earth's crust. (They are often heated by the same sources that produce the volcanoes and fumaroles.)

In active volcanic zones such as Yellowstone, water may be heated by coming into contact with magma (molten rock). The high temperature gradient near magma may cause water to be heated enough that it boils or becomes superheated. If the water becomes so hot that it builds steam pressure and erupts in a jet above the surface of the Earth, it produces a geyser.

Several hot springs exist in Alaska. (See map above)
The most famous of these is Chena Hot Springs, located in Alaska's interior about 60 miles from Fairbanks.