|Copyright: Bob Harrison (BobH)
|Date Taken: 2007-10-06|
|Camera: Canon PowerShot S2 IS|
|Exposure: f/3.5, 1/500 seconds|
|Photo Version: Original Version|
|Date Submitted: 2007-12-08 7:38|
|[Note Guidelines] Photographer's Note|
|In a previous post ("tenacity"), I mentioned how it is common to see trees growing in Maine without visible soil. If you live in a tropical environment, this may seem strange, but in post-glacial Maine, it is part of the normal process of life reasserting its grip on the land. This photo, taken on the same lake as my earlier "minimalist grass art" post, shows a small island which is actively engaged in that process. |
Much of Maine was scraped to bedrock during the last ice age and is gradually accumulating soil to cover the scars. Maine's rocky coast, with its inlets and islands so loved by tourists, is one manifestation of this. Inland parts of the state show a different side of the process, especially in rocky freshwater lakes. The soil building process occurs differently at the ocean's edge than in a lake ecosystem, for obvious reasons such as salt, tide, and oceanic moderation of temperature.
The islands dotting Maine's many lakes and ponds illustrate the full range of soil building, which can be quite delayed compared to the mainland. The largest islands are biologically very similar to the mainland- lots of soil, large trees, and abundant wildlife. The smallest islands are mere rocks in the water, sometimes awash during storms. Whether these rocks can be called islands at all may be an important semantic issue to some. But these not-quite-islands nonetheless represent a key point on the same broad continuum of ecological succession that extends backward in time from the larger islands.
This island is near the delayed end of that continuum. It is a single granite boulder several hundred meters from shore, part of a group of small islands made up of glacial erratics sometimes 20 m across. Some of these islands have multiple rocks harboring a substantial amount of soil and even large trees, some as tall as 30 m. Some of the islands are isolated rocks with only lichens up high and algae near the waterline. This island is in between, colonized, but not yet subdued by life. Yet it is an ecosystem unto itself, with one nearly mature tree, two young trees, grasses, mosses, lichens, algae, and small but growing pockets of soil.
The main feature of this island is the vertical cleft from which the biggest tree is growing, the result of uncounted freeze-thaw cycles over thousands of years. What looks like a single rock is probably cracked through, but not yet separated. The deterioration on the right side of the cleft has already sent nearly a half meter of rock crumbling into the lake, to become the underwater foundation of a future beach. The wedge shaped block filling the cleft is under attack from all sides and will not last long. The tree's roots, drawing unlimited water from the lake and seeking nutrients from the growing deposit of soil in the cleft, will help remove the block from the cleft.
The assault on the rock's integrity is visible on several fronts at once. The inevitable cleavage down the middle will open a gap that can accumulate soil and stabilizing vegetation. The right side peak of the rock appears designated for removal soon (geologically speaking), since it is marked by a wide crack with highly weathered edges. The long thin line of moss to the right of the tree defines another line of attack, already centuries along. The small trees may eventually accomplish as much in their own cracks as the large tree and its predecessors have in the center cleft.
Come back in a few thousand years and you may find only a gravelly beach like the one at the north end of the lake.
tech notes- simple cropping and some slight PS adjustments- shadow lightening, contrast, brightness, total color saturation
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