Photo Credit: Frank Kovalchek

Exploring the Kenai Mountains-Turnagain Arm National Heritage Area: Tern Lake

f12-1GEOLOGY AND THE EFFECTS OF ROAD CONSTRUCTION

Location:  TERN LAKE:  Mile 0 of Sterling Highway – Just West of Junction

Short Description:  This stop has a two purposes: to observe a slow motion sloughing  of a mountain and confront what we take for granted actually was a result of human disturbance.

Required Equipment: Photo of Mountain, Old Map of Area (included),

Suggested Equipment: Binoculars

Safety Consideration: None

Other Info:

f12-2

  • Mountain visuals will be obscured by low clouds.
  • If desired, instead of the pull-off, a picnic area is located 1/4 mile down the Sterling Highway with pit toilets.

 

 

 

 

Inquiry Prompts:  What’s Going On Here?

tern lake


1) The Mountain behind Tern Lake:

This is a tough observation, however, take a look at the top third of the predominate mountain to the south. You’ll note a bulge a third of the way down the right (west) side of the mountain. Just another feature? Or is something going on? Something is going on. This section of the mountain is unstable and is slowly creeping down the mountainside. It likely has been happening for many, many ages. Likely it is a result of over-steepening of hillside by glacial scouring. However there will come a time (just like the hillside south of Hope Junction) where gravity will win. It isn’t without precedent. These massive failings have been famously documented many times such as in Lituya Bay and in Glacier Bay in the summer of 2012. Although not of these magnitudes, the collapse of this shoulder above Tern Lake would certainly have an effect in this valley.

But there’s more:

Provide students with a copy of the map attached to this lesson.  This  map details this area with one glaring omission . . . Tern Lake.

So, something happened between the time the map was drawn to now to create this lake. And that something was the construction and modernization of the Sterling and Seward Highways. These highways constricted the flow of water creating this lovely shallow lake. However, it perhaps wasn’t always lovely. Imagine what the area looked like prior to the succession of marsh plants. Perhaps the original name for Tern Lake would help— Mud Lake.

 

Perhaps it took awhile, however little did anyone realize during the construction phase that the resulting lake would be a favorite spot for swans in the summer, and skaters in the winter.

 

 

f12-4