Saturday, December 28, 2019

Indiana Dunes

Wind, and therefore waves, blowing down Lake Michigan (on both sides), results in southward sediment transport and the accumulation of sand towards the south end of the lake. Here on the southeastern corner, the sand has built a robust series of dunes (many of them now well back from the advancing shoreline and largely transformed into forested ridges separated by linear wetlands).

These photos don't show it, but I could see the Chicago skyline across the lake (still a long ways away). What you do see in these photos are the stacks of steel mills and generating plants in the middle distance. It's nice that the Indiana Dunes (a State Park) preserve some natural shoreline on a coast that has suffered historically from intense industrial development (and much now in disrepair).


Ironically, today's wind was blowing strongly from the south and this leeward shore was welcome relief. I actually modified my route the last couple of days specifically to avoid the strong winds blowing north along Michigan's shoreline. By tomorrow (September 4th), unfortunately, they will be from the north again as I turn the corner and ride into Chicago.

Sodus Point

My route west paralleled the shore of Lake Ontario, but was generally far enough inland to miss most of the shoreline itself. One exception was at Sodus Point, where I rode out to the beach and followed the 'coast' for a few miles west before heading south again. These photos were taken back in late August (yes, I am a long way behind).

The north-facing shoreline of Lake Ontario in New York State consists of bluffs and a series of barrier beaches built across the mouths of north trending valleys. I'm not sure whether to call the drowned stream mouths and lagoons behind the barriers estuaries or not - it sort of depends on whether you define estuaries around salt water (this is a freshwater system), or around their physical geomorphology (which works for me).


I don't know much about this shoreline, other than from a few articles over the years and from what I can infer from the maps and imagery. Sediment transport along the beaches is generally from west to east and this is clearly shown by the assymetric build up of material at jetties. Big wide beaches on the west sides (like here at Sodus Point), and very thin, sketchy barriers on the east sides.

The Great Lakes have been running pretty high and Lake Ontario is no exception. This fall there were news stories about funding efforts to address flooding and erosion at a variety of spots along this coast both east and west of Rochester (including the sediment-starved barrier immediately east of these jetties). Water levels on the Great Lakes vary over cycles of many years as the large watershed is a great integrator of long-term regional hydrologic patterns.

Friday, December 13, 2019

Long Lake

I don't think beaches are pervasive features on lakes in the Adirondacks, but they are found locally. In most cases, the forest comes right down to the water's edge and I guess there's not enough sediment, and not the appropriate wave environment, to maintain beaches. But the presence of coarse-grained igneous rocks (anorthosites) that erode to form sand-size material and a glacial legacy of scour and redeposition suggests to me that enough sediment might be available in some places, if the wind and wave conditions are sufficient. On the other hand, a cursory look at Google's imagery suggests that many of the small beaches may have benefited from a human hand (and some dump truck loads of sand). 

I spent a night in late August near this one on Long Lake. Which was long enough to appreciate the beautiful evening and subsequent morning, but not enough to actually learn much about the beach or even the local geology.

I did learn that the one thing that all beaches in the Adirondacks have in common are the chairs.