A Natural History of Lake Ontario by Susan P. Gateley

Author:Susan P. Gateley
Language: eng
Format: epub
Publisher: Arcadia Publishing Inc.
Published: 2021-01-15T00:00:00+00:00

STONE STORIES

The lake’s south-shore beaches with their colorful variety of rocks are a pebble picker’s delight. As it moved southwest, the glacier picked up rocks from different locations. When it melted away, the rocks remained behind, dumped together in a multicultural mix. Ancient metamorphic gneiss (rhymes with “mice”) from the Thousand Islands area and the Canadian shield, granite and dark sparkly schist from the Adirondacks and Ordovician limestone from the Canadian side of the lake now lie side by side on the beach. They and other sedimentary and metamorphic rocks create a delightful mosaic of colors, textures and shapes on south-shore beaches.

Around Sackets Harbor and Chaumont as well as on the Canadian shore around Kingston and eastern Prince Edward County, gray limestone pebbles predominate. Most of the beach pebbles on New York’s south shore are of either various colors of sedimentary sandstone or limestone or have metamorphic origins. Sometimes, the keen-eyed beachcomber may also see a few rocks of human origins. You might occasionally encounter water-rounded bits of concrete or brick that recall the fate of a cottage or some other man-made structure that once stood on an eroding shore. I’ve found odd water-rounded “pumice”-like clinkers and bits of slag as well as pieces of gray dolomite rock broken off of some of the boulders that have been imported by people to protect shorelines. Once or twice, I’ve found water-rounded gray beach stones from these imported boulders that have hollows, or “vugs,” containing small crystals. So you never know what oddities might show up among the native sandstone or other pebbles left by the glacier on the neighborhood beach.

Freshly eroded rocks recently released from the shoreline banks and bluffs usually have angular shapes and edges. After a few years of beach life, they become the water-rounded pebbles that skitter and roll so readily underfoot. However, a close look at the stones still embedded in the bluff ’s clay reveal that some of them show signs of some water-rounding that must have occurred long before Lake Ontario existed. Now and then, a really big rock ends up on the shore or in the lake. They can be of various types; some are sandstone or limestone, others are metamorphic granite or gneiss. These are glacial erratics, some of which were carried long distances by the ice.

Not long ago, I encountered two refrigerator-sized boulders recently eroded out from the shoreline. Both appeared to be of identical granite-like rock, ancient metamorphic rocks that may have originated from the Canadian Shield to the north. Both were clearly somewhat water- or ice-rounded.

I thought they looked like siblings. Perhaps they were both broken off of a larger mass of rock eons ago by the glacier. Perhaps they were then dragged around and shaped by the ice. Or perhaps, after forming a billion year ago miles below the earth’s surface in the deep time of geology, they somehow journeyed to the surface to then be shaped by water action. Maybe at some point in their lives they were

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