One of the real treats for me on this recent trip up north was visiting my first drumlin. My friend Paul Tomascak teaches geology at SUNY Oswego, and Oswego is surrounded by drumlins:


Another concentration of drumlins, a little further to the southwest:

So what's a drumlin? A drumlin is an elliptical hill of till, with a distinctive upside-down-spoon shape. It's steeper at one end, and more gently tapered at the other end. Drumlins occur in drumlin fields, all oriented the same direction, as you can see on the maps above. The exact mechanism of their formation is not fully understood. Despite being enigmatic, they are (a) clearly associated with continental glaciation (the Pleistocene North American ice sheet, in this case) and (b) are oriented with their steep side towards the up-ice-flow direction, and their tapered side pointed downstream.

I love the word drumlin, & still have plans to name my dog Drumlin someday (when I get a dog).

In some places, the drumlins are dissected by the erosive action of the waves of Lake Ontario:


Paul took us to one such "half-drumlin," shown here to be McIntyre's Bluff:


Here's the satellite view (a bit more zoomed-in) so you can get a sense of the gullying style of erosion as the till composing the drumlin succumbs to wave action, rainfall, and mass wasting:

In the car, approaching one of the drumlins we had to traverse on the drive there:

Here's the view from the top of 'the bluffs' -- note the tiny little patches of grassland still remaining (erosional remnants) as the underlying till gets eroded.

Closer view of the same area, so you can see the poor sorting of the till:

Slump blocks carry grass and soil profiles downward and outward:

Paul tells me that this till varyies tremendously in its character, depending on whether it's wet or dry. If it's dry (like it was when we visit), then it is extremely hard, essentially like concrete. Limestone powder and mud flakes bond the whole mess together into a very tough outcrop. When it's wet, though, the calcite must dissolve and the mud gets slippery, and the whole mass becomes a big soggy sloppy mess. Paul told of an undergraduate student who stepped in it, sunk in to her hips, and lost both shoes, both socks, and her pants (!) when her peers pulled her out.

From below, walking up the beach below the bluffs... Paul in the middle distance:

Driftwood like this likely acts as "battering rams," tools which carve more effectively at the base of the bluffs than wave action alone, especially during storms.

Paul and Lily discuss the sorting of the sediments by the lake (note the gravel beach, and the lake water's suspended load close to shore):

Classic glacial cobble: faceted, with a Scarface worthy collection of scratches. This is a limestone cobble, and they tend to show the scratches the best of the varying lithologies that make up the clasts in the till.

But there are other kinds of rock there too, like this lovely piece of the Canadian Shield:

Tower of till, dissected and eroded, as viewed from below:

I collected some nice glacial cobbles here for the NOVA teaching collection, plus a whopper of an amphibolite with nickel-sized garnets. (I really wanted that granitic gneiss with the folds and boudinage, but it was too big to haul out.) Sigh... Great place; thanks for taking us there, Paul!