Yellowstone Lake

The beaches on Yellowstone Lake have always fascinated me. They are built of mixed sand and gravel and come in a combination of eroding bluffs and assorted barrier beaches. I'm convinced (without much serious investigation) that they may be impacted by medium-term changes in not only absolute lake level but in relative lake level (Yellowstone, particularly here at the north end of the lake, rises and falls with the underlying magma pool).

AERIAL VIEW

Here's a post from more than a decade ago: Yellowstone Lake: July 2007.

Photos here are from late September 2019.

Lake DeSmet

Last week, we were back on the road again between Washington and Minnesota. It was a fairly quick trip, so there wasn't much time to explore, but I did find one beach worth noting. I found it early the third morning of the trip pretty much by accident, since I was only looking for early sun on the Big Horns northeast of Buffalo (Wyoming).  I came around the corner and here was this wonderful red gravel beach!

Lake DeSmet began as a natural lake, although it has since been enlarged and turned into a reservoir.

Google Maps:  Aerial View

The hills surrounding the lake are Tertiary sedimentary rocks, marked by resistant outcroppings of clinker. Clinker is a red or black rock that results when coal seams burn and bake the overlying sediments (see Callan Bentley's Mountain Beltway Blog at AGU). It's common in the Powder River Basin (because there's so much coal - see hshipman: Black Thunder Mine 2012).

This beach was at the south end of the lake, next to the dam, and consisted entirely of gravel-sized clinker. There were a series of berms marking higher lake levels. The beach was swash-aligned, oriented pretty much straight into the northwesterly fetch - the winds can get pretty fierce around here.

Farther west, the red gravel stacked up nicely against the limestone riprap of the dam. And at the boat launch on the southwest corner of the lake, there was a neat little clinker spit built across the mouth of a drowned creek mouth (drowned by the reservoir).


(For non-beach photos of our ten-day road trip:
hshipman:  roadtrip 2013)

Headwaters

Six weeks ago I was in New Orleans, not far from where the Mississippi enters the Gulf of Mexico. Almost 3900 miles upstream, in Yellowstone Park, the Firehole and Gibbon Rivers join to form the Madison River. The Madison joins the Jefferson and Gallatin Rivers in Three Forks, Montana, to form the Missouri River, which in turn joins the Mississippi at St. Louis. It's a long way from the hot springs of Yellowstone to the French Quarter.

Yellowstone Lake

Some of my favorite gravel beaches are these barriers on Yellowstone Lake. I saw them first by accident about a dozen years ago - although my recollection is that the lake level was considerably higher. I believe on that trip, the beaches at the north end were almost submerged, whereas they seemed just the opposite this year. I'll have to see if I have some pictures from back then.

Although the lake is ultimately volcanic in origin - it fills a large part of the Yellowstone Caldera - these beaches are built of glacial sediments. The pictures include the north end near Sedge's Creek, a beach south of Bridge Bay, and a site on the western shore north of West Thumb. Maps and online aerial imagery show many more elegant barriers around the lake, each probably jealously guarded by its own grizzly bear.