A land made of sand

Looking north along the shoreline towards the Big Sable lighthouse on the eastern shore of Lake Michigan

A little family vacation this year means a trip to Michigan, and a few days spent in my wife's childhood summertime haunts near Ludington, Michigan.  We've spent most of our time in Ludington State Park, which sits on the incredible Big Sable Point.  As far as I can tell the whole landscape here is basically a big pile of sand blown out of Lake Michigan, which makes for a prime opportunity to check out various sand transport processes at play, and their resulting landforms.  So first off, a reminder (mostly for my benefit) that the vast body of water that we've been gazing out on to our west:

is, indeed fresh:

but the process scales here ARE extraordinary, and very ocean-like in many ways.  There are actually tides at play, though they are small.  But there are larger water level variations (of around 4 feet based on the last 50 years of record) driven by an interaction between precipitation, evaporation, outflow, and seiches (which seem to be driving little 1 inch sub-hourly variations in water level over the last day).  Waves are clearly a force here - I geeked out for a bit on these little lines on the shoreline, each deposited by an individual wave scouring sand from the beach face and pushing it landward.  

at the same time there are signs of erosion everywhere, not only indicated by the seawall built to protect the Big Sable lighthouse (photo at top), but also by the erosional scarp along most of the lake edge:

But wind is clearly the main player here.  My guess is that periods of low lake level lead to drying of shoreline sand, and rapid aeolian transport.  The resulting dunes are impressive:

and clearly mobile (as indicated by the complex stratigraphy exposed on this dune):

Dune grass (an Ammophila species, though I'm not sure which one - but may be native here?) is widespread (and so impressive in its ability to survive in this environment):

and probably contributes in some way to dune stability.  I was struck, though, looking at Google Earth Engine's timelapse, at how LITTLE obvious dune migration there is over the last 30 years:


I have no idea how much dune grass contributes to that stability.  But, as in a lot of locations Ammophila DOES contribute to the creation of a distinctive dune morphology.  Here is a beautiful view looking down the trough between the primary foredune (to the left in the field of view) and the secondary dune (to the right):

Behind the secondary dunes is a wonderland.  Currently the lake is pretty high, and there has been recent rain, so the landscape is peppered with these beautiful little ponds:

Interestingly, in this particular location the ridges between these ponds were actually paved with these gravel cobble lag deposits, which were beautiful...but also a bit odd to try to figure out how they ended up here.  Anyone want to take a stab?