Scarborough Bluffs

East of Toronto are several miles of high bluffs, apparently a slice across the front of a thick delta deposited long prior to the last glaciation. The toe of the bluffs has been largely stabilized through revetments (both of construction debris and of more of the elegant dolostone seawalls and revetments so common on the lake), groin fields, broad beach fills, and a large lake fill (Bluffers Park). Longshore drift is to the west, so erosion of these bluffs may have fed the spits and shoals that formed the natural precursors to the now heavily modified Leslie Street Spit and the Ontario Islands off the Toronto waterfront.

Cabot Head

Cabot Head lies on a low foreland that extends out in front of the escarpment and that encompasses several wetlands and lakes, including Wingfield Basin, which may have begun as a small lake but is now a lagoon with a shallow entrance to Lake Huron (Georgian Bay).

The gravel road from Dyer Bay out the lighthouse follows a great cobble beach, but what was most amazing was the incredible series of shingle beach ridges on the east side of the point. Shingle - since the rocks are all 6-inch flagstones, all weathered by the several thousand years that has passed since they were last tossed by waves. The fact that they aren't very rounded may indicate that they weren't in the swash zone for very long - a sign of rapidly falling lake levels at the time?

Halfway Log Dump

Early Sunday morning and I have the entire place to myself. This is worth the long weekend, the 2500 mile flight with a coffee stop at O'Hare, the 200 miles of driving, and the 1km walk through the woods. I'd do it again.

Another beautiful gravel/cobble beach on the shores of Georgian Bay. Dolomite ledges to the east with white dolostone cobbles scattered across the surface, lined up in the crevices, and piled against the low seacliff. The broad flat ledge was 1-2 feet above lake level, which made walking the shore simple, but I saw a picture in town yesterday showing the ledges below lake level.

A small sea stack. Ancient white cedars growing out of cracks in the rocks. And a rounded knoll on the platform that I suspect was a particularly dense part of the coral reef that was forming here a mere 400 million years ago.

Singing Sands

The northeastern shore of the Bruce Peninsula is steep, with the escarpment plunging into Georgian Bay. The southwestern shore is low, as the dolostone layers dip gradually into Lake Huron. This leads to an irregular shoreline with promontories and inlets. There's also sand (eroded from glacial deposits on the upland and delivered to the shore by streams), something I didn't see at all on the other side of the peninsula.

Singing Sands is the name given to the dunes and broad beach at the head of Dorcas Bay. The already broad beach is even broader thanks to the recent low lake levels. Plants are already colonizing the new flats. Sand is juxtaposed with the carbonate bedrock. In Hawaii in April, I saw sandy beaches on 120,000 year old limestone (on 5 million year old islands). Here, the beach lies on top of 400 million year old limestone.

Flowerpot Island

The flowerpots are two elegant sea stacks of thinly bedded dolostone on the east side of the island. From the tour boat, I thought the upper surface of the stacks looked suspiciously unnatural and later I read something that indicated that maybe efforts have been made to shore them up. It is always a shame when erosion and the passage of time wipe out the symbol of your community, or the primary destination of your local tour operators! New Hampshire reinforced the Old Man of the Mountain with steel and concrete, though eventually he came down anyway.

Storm Haven

Most folks stick to the simple loop out to Indian Head Cove, the Grotto, and Marr Lake -- lots fewer make the short hike farther east. The trail follows the higher beach ridges and then climbs into the woods and along the cliffs (with some great views), before dropping back down to the cobble beach at Storm Haven.

There were boulders and collapsed chunks of the escarpment in both directions. The beach ridges extend back up the slope and into the trees, the old ridges dating from the higher lake levels of thousands of years ago. The dolostone ledges are thinly bedded and break into angular flagstones which work their way down the beach as talus. They gradually merge with the wave-rounded cobbles that mark the lower beach. It's all the same basic stuff. In the middle, you end up with a nice mixture of angular bricks and rounded cobbles.

The deepest portion of Georgian Bay (170 meters - 560 feet) is located not far from here, and within a couple of kilometers of shore, indicating that the cliffs we see above lake level are just the upper part of a much more extensive landform.

Bruce Peninsula

The Bruce Peninsula is where the Niagara Escarpment slides into Lake Huron (Tobermory is the little town at the tip). It re-emerges a little farther north as Manitoulin Island and separates Lake Huron from Georgian Bay. Its gently rolling surface is marked by wetlands and dolostone barrens called alvars. Unlike the extensive farmland on the glacial deposits to the south, the Bruce is largely forested in pine and white cedar. The steep outer edge of the escarpment forms the northeastern shoreline of the peninsula. The western shoreline slides gradually into Lake Huron.

Niagara Escarpment

The Michigan Basin is underlain by a thick series of very old rocks, including layers of carbonate rocks deposited in warm seas over 400 million years ago. These sedimentary rocks are basically limestone, but the addition of magnesium has turned the calcite to dolomite and the resulting rock to dolostone. These resistant layers are deepest under Michigan, but like a large saucer, tilt gradually upwards until they break the surface in a large arc around the Great Lakes. These rocks form the Niagara Escarpment, a low hogsback (or cuesta) with a gradual slope on the inner (Michigan) side and a steeper cliff or bluff on the outward facing edge.

The escarpment runs from western New York State north into Canada, around the western end of Lake Ontario, and north across the farmland of southern Ontario. It forms the Bruce Peninsula and Manitoulin Island, between Lake Huron and Georgian Bay, and then sweeps across the upper peninsula of Michigan before heading south to form the Dore Peninsula and Green Bay in Wisconsin (thus the geologic similarity of the Buffalo Bills and the Green Bay Packers?). Streams flowing across the escarpment form cascades, Niagara Falls being the most obvious.

Inverhuron

Inverhuron Provincial Park lies north of Kincardine on the southeastern shore of Lake Huron. At Gunn Point, the receding lake had abandoned a nice gravel beach ridge back among the trees and left a broad platform that plants are trying to colonize. On the bay to the south, a nice set of dunes had formed and still farther south, cottages lined a beach with a narrow sandy beach and rock ledges exposed on the recently exposed lake bottom.

Looking north from Gunn Point, I could see Douglas Point and the Bruce Generating Station, the largest nuclear power plant in North America and the second largest in the world (Wikipedia). I suppose it's the existing transmission infrastructure that makes the big wind farm just inland from here possible. I admit, the wind turbines were much prettier in the late afternoon sun than the boxy nuclear plant.

Lake Huron is the third largest lake in the world - and probably larger if you count Lake Michigan, which is really part of the same lake. It's been ratcheting downward for thousands of years, although relatively high water in the 1980s caused lots of erosion problems. The last few years it has continued to fall and is near record levels now. This is partly due to regional hydrology - maybe less rain - but it may also be due to human changes at the outlet near Detroit. Once again, we can credit regional changes in the environmental landscape to the Corps of Engineers!

Oakville

If you are going to bury a beach under big rock, it makes sense to do it right. In southern Ontario, limestone (dolostone, actually) is plentiful and has the strength and the blocky fabric to make great stackable armor stone. In Puget Sound, we are cursed with an abundance of crumbly marine basalt and our shorelines are the worse for it.

I loved the way the gravel was piled up against the seawall. Coarser sediment tends to do this, even when finer stuff is getting pulled offshore. The flat pebbles are probably made of the same basic stuff as the seawall. I bet the late fall storm waves toss it over the seawall (winter storms just blow across the ice).