• Winter in the Wrangells

    Wrangell - St Elias

    National Park & Preserve Alaska

Forces of Change

Rock and Ice

Wrangell-St. Elias National Park and Preserve is a fantastic laboratory and its extraordinary collection of mountains and geologic features was one of the primary reasons for the creation of the park.

The mountains here are impressive. Four ranges exist within the park - the Wrangell Mountains, St. Elias Mountains, Chugach Mountains, and the Alaska Range (Mentasta/Nutzotin Mountains) - and were created by the collisions of plates in the earth's crust. Many of the peaks within the Wrangell Mountains were once active volcanoes. Today, only Mount Wrangell (14,163') remains active.

Geologist have concluded that the bedrock underlying these mountains formed much further south than its present position, perhaps off of California. The movement of this terrane northward and its collision with other crustal plates caused volcanic activity, subduction, and uplift resulting in massive mountain ranges in Alaska. These plate tectonics remain an active and powerful force of change today.

On November 3, 2002 a massive 7.9 magnitude earthquake located in the central Alaska Range extended eastward along the Denali and Toshunda faults, rocking the northern district of the park. Displacement of the fault reached 5 meters in places. Damage to roads and personal property was extensive, but nobody was killed or seriously injured. This earthquake caused incredible changes to the topography of the region. Bedrock fractures were reactivated, cracks appeared in the surface and mountainsides, and huge mudslides came down many slopes. Scientists will be studying the impact of this earthquake for many years.

Glaciers are the headwaters for many of the river systems that flow like arteries through the park. They are heavy with glacier silt and sediment, causing them to braid as one channel begins to fill with sediment forcing the water to switch to a new channel. Glaciers themselves are often referred to as rivers of ice. They flow down mountain valleys and, in the case of tidewater glaciers, into the sea. We don't generally expect to see movement or experience the results of this movement, but glaciers, like other geologic forces, are dynamic.

During the summer of 2002 the Hubbard Glacier near Yakutat pulsed forward, closing Russell Fiord from the sea. The massive ice dam that formed was later breached and washed out by water retained behind it, reconnecting the fiord to the ocean. Rather than being an event that took hundreds of years, this drama played out in the course of a couple of months.

As you travel throughout the park, imagine the forces and processes of change that created the beautiful scenery and then remember that those same forces continue their work today. This place looks different now than it did six months ago...what will it look like when you visit?

Did You Know?