sandstone island trail

Several of our favourite hiking trails are located at Charleston Lake Provincial Park in eastern Ontario. Situated on the eastern edge of the Canadian Shield, the Charleston Lake area is of great geological interest. Here, ancient Precambrian granite of the Shield lies in contact with sediment deposited when Paleozoic seas washed over many parts of North America about 480 million years ago. Evidence of more recent glacial activity can be seen along many of the park’s trails. On the high, exposed stone ridges, the rock is often deeply gouged and grooved. Huge erratics lie wherever they were dropped by receding glaciers. Sandstone over conglomerate may be found resting atop the ancient granite bedrock. Unusual rock formations reveal erosion resulting from water flowing from melting glaciers.

The Sandstone Island Trail is one of the best places in the park to see a variety of geological features. The “Sandstone Island” name is derived, not from an island in the usual sense, but for the Paleozoic age sandstone layer which rests atop the older Precambrian granite, forming a great island of stone. The sandstone and underlying conglomerate rubble are visible at many sites along the low cliffs bordering the trail. The most dramatic of these is the “rock shelter” where a massive section of sandstone projects several meters beyond the underlying layer of conglomerate lying atop the granite bedrock (click on above and photo to left to see larger views). Over time, the conglomerate layer has eroded, leaving the sandstone overhang. At other points along the sandstone cliffs, great sections the size of a large truck have broken free and tipped or rolled downwards to their final resting place. Several of these immense chunks of sandstone and conglomerate may be found near the trailhead.

The “rock shelter” (both of above photos) is of interest for its history as well as its geology. Artifacts such at potsherds have been found during excavations of this site, indicating that the ledge has been used as a shelter for many centuries.

A bit further along the trail lies another extraordinary feature — the remnants of a waterfall eroded into the side of a sandstone cliff. Thousands of years ago, water flowed over the cliff to wear an almost perfect semicircle. Near the top, one rectangular chunk of stone projects from the smoothly rounded sides of the waterfall. There’s something about this place that always tweaks my imagination a little. It feels like a place of power and makes me wonder if, long ago, travelers might have left tobacco or other offerings to the spirits of the surrounding lake and forest. Just beyond the waterfall, the trail ascends to the top of the sandstone caprock and continues on through upland forest. Several expanses of exposed stone reveal glacial wear and an erratic or two.

Added later: This webpage, Geology of the Rideau Region contains info and linked maps pertaining to the general area of Charleston Lake. This map shows an area just slightly to the west of Charleston Lake (Charleston Lake lies just a few kilometers east of the section around Morton).

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4 Responses to “sandstone island trail”

  1. Duncan Says:

    There’s something about a cave or overhang that strikes a chord deep within our subconscious, an echo of our distant past perhaps.

  2. Peter Says:

    I first hiked this trail in the late 80’s, when I was about 10 years old, and have visited every few years since. Breath taking scenery.

  3. burning silo Says:

    Peter – yes it is wonderful scenery and you’re very lucky to have been able to hike the Charleston Lake area 20 years ago. It’s still a super place to hike, but does feel some pressure from the human footprint.

  4. Burning Silo » Blog Archive » late november at hemlock ridge Says:

    […] The final part of our hike led us along the trail where it passes through a narrow slot between a sandstone ledge and immense fragments of the ledge that have broken away and tipped over onto the downhill side of a steep slope leading to a pond filled basin (see photo below). The sandstone lies atop the granite bedrock beneath, and as erosion has weakened the sandstone layer, sections of the ledge have fallen away. In this photo, Sabrina is seen standing in one of the sections of trail where the uphill side ledge is not so high. In places, it is roughly 3 meters (about 10 feet) or so high. For a better feel for the geology, check out this post that I wrote about the Sandstone Island Trail, which is located not far from the trails hiked yesterday. As you can see in this photo taken from beneath a sandstone ledge in the Rock Shelter, the ledge gradually erodes until the cantilevered “shelf” someday falls and tips to the forest floor (hopefully when there’s no one around!). […]