While the land under our feet seems stable and permanent, it is, in fact, very dynamic. The earth is made up of massive plates of rock, about 50 miles thick, that float in slow motion on top of the earth's mantle.
New seabed is constantly being created in the middle of the oceans. To make room for the continual addition of new ocean crust, all the Earth's plates move at speeds of between 1cm and 10cm every year (about the speed at which fingernails grow). As they move, intense geologic activity occurs at the plate edges.
As the Pacific Plate grows, the spreading sea flow crashes into the terrestrial plates of North and South America and Asia. This interaction creates the most intense geological interactions on the planet and is known as the Ring of Fire.
In fact, 90% of the world's earthquakes and 75% of the world's volcanoes occur along the Ring of Fire. In the last 10,000 years, all but three of the 25 largest volcanic eruptions in the world have happened on the Ring of Fire.
Volcanoes on Ring of Fire
Mt. Redoubt in Cook Inlet
Part of the Aleutian Volcanoes
Being part of the Ring of Fire has important consequences for Alaska. The interaction of the Pacific Plate and North American Plate has directly created many Alaska landforms, including the Aleutian Trench, Aleutian Volcanoes, the Alaska Range, and the Kenai Mountains.
Being part of the Ring of Fire also means Alaska is very seismically active. In fact, Alaska averages 30,000 to 40,000 earthquakes a year—that is one about every 15 minutes! The 1964 Good Friday Earthquake was the second-largest earthquake ever recorded in history, causing 139 deaths. This photograph shows the damage from the Good Friday Earthquake in downtown Anchorage.
Downtown Anchorage after Good Friday Earthquake
