Photo Credit: Frank Kovalchek

Exploring the Kenai Mountains-Turnagain Arm National Heritage Area: Land Subsidence

F7-1DYNAMIC EARTH SUBSIDENCE

Location:   Mile 56.6 Just South of Hope Cut Off

Short Description:   As you leave Hope Junction going south; take note of the hillside on the right.  There is no good place to park; no good place for students to disembark bus, however it is still a interesting visual.

Required Equipment: None

Suggested Equipment: None

Safety Consideration: No place to park except on shoulder

Other Info: None

Inquiry Prompts:  What’s Going On Here?

Have students take a gander at the hillside. The entire hillside should look “wrong”. They may not even be able to describe why… it just doesn’t look right. Look at the trees, look at the ground, look at the exposed rock. Something just doesn’t look right. In contrast to stable road cuts, these exposures look broken up and pieces of rocks look like they have shifted relative to one another. What’s going on here?

F7-2The Rest of the Story:

This hillside is failing. Not just the ground setting on the bed rock, but indeed the entire bedrock is failing and slowly (currently) working its way down the hill.

All along the Kenai Mountains-Turnagain Arm National Heritage Area, it is not uncommon to see large swaths of soil slip from its bedrock anchor (especially during severe wet stretches) but this is different. This is actually the bedrock that is splintering.

Eventually, hopefully not while your bus is parked there, gravity will win and the stress will cause the hillside to end up on the road. It’s a reminder that this is a very dynamic and ever-changing landscape .