The Racetrack Creek Moraine

January 03, 2021  •  Leave a Comment

RacetrackRacetrackThe Racetrack Creek glacial moraines from Sand Hollow, Road. November 29, 2020. It's been more than a month since my last blog posting and feel that I 'owe' us one. I was mostly busy getting through Christmas, but also in a dry spell with few new photos I wanted to talk about.

During the last ice age, the Flint Creek range hosted alpine glaciers that carved its mountainous topography and extended down the valleys of Rock, Tin Cup Joe, Dempsey, and Racetrack Creeks into the Deer Lodge Valley. Of the four, the Racetrack Creek glacier left the most distinctive glacial landforms behind. 

I have often looked at the Racetrack Creek deposits on satellite photos. From space, the moraines are striking -- a neat glacial package of lateral and terminal morainal deposits that outline the maximum extent of this small alpine glacier about 10,000-12,000 years ago. 

I have been trying to get a good photo of Racetrack moraines for some time, but finding an angle that shows their distinct beauty is difficult. If you are too far away, the landforms blend into the rest of the landscape. Up close, they are amazingly large and you cannot really see how they fit together.

In November 2020, I caught this late-day, low-sun-angle view of the Racetrack Creek moraines from Sand Hollow Road--directly across from Racetrack Creek--on the east side of the Deer Lodge Valley. The sun highlighted the Racetrack glacier's parallel curved lateral moraines that extend eastward from the mountains.

The glacier exited the Flint Creek Range through the deep canyon that lines up between the lateral moraines. The timbered, relatively low, rumpled, topography in the mid-ground is the glacier's terminal moraine. Here the eastward movement of the ice matched the rate of melting and the ice front stopped. At the terminus, ice broke off from the main flow, became trapped in the glacial debris that it was carrying, and melted in place. The flat landscape in front of the terminal moraine is the outwash plain where meltwater deposited sand, gravel, and boulders. Strong braided stream patterns appear on satellite photos immediately east of the terminal moraine.

Take a moment to find this glacial story on a satellite view of the Deer Lodge Valley in Western Montana. It is just pretty.

Thanks for reading!


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