When did homo sapiens arise? Maybe 2 million years ago?
Nobody really knows exactly when we became “human,” but most of the rocks on our Lake Ontario beaches are at least a hundred times older than our species.
This is what the geologists mean by “deep time.”
Rocks, I have learned, lead more exciting lives than you might imagine. They are born, grow, crystallize, dissolve and re-form, changing ultimately to become clay or sand only to again become rock. This has been going on for about 4 billion years.
The geologists call the process The Rock Cycle. Just as souls in some religious beliefs are re-born, stones and boulders too undergo reincarnation. Rocks buried miles deep, are melted and transformed into new rocks, only to be uplifted by tectonics or erosion. Then weathering begins to transform them yet again.
Ontario’s south shore beaches are unusual. Thanks to glacier transport, the rocks and gravel came from many places to gather here. They include pebbles from the ancient rock of the Canadian Shield and the Adirondacks as well as more “local” sandstone and limestone pebbles.
One distinctive rock type I began collecting as a child is the “lucky rock.” According to local lore, the lucky ones are black pebbles with white bands of a crystalline mineral called calcium carbonate that circle the stone. The distinctive bands are formed after the stone cracked apart deep underground. Water saturated with minerals then bathed it and over time, the mineral precipitated and bonded the two pieces of rock back together. So lucky rocks really are fortunate to have survived their journey through time.
The Lake Ontario beach is a part of a system that is more complex and dynamic than we imagine. Who knew the life of a pebble could be so filled with adventure? You erode out of the drumlin, tumble down to join the rest of the crowd, and here’s the water again – after ten thousand years of waiting inside a hill. Tumbling, rolling, crashing, smashing (at least if you’re not too big), you move along the shore at a right good clip. Some days you might travel several hundred feet.
Perhaps a really big storm hits and you end up in an “over-wash” and now you’re hanging out at the bar. The barrier bar that is. How long will you stay? Seedlings of cottonwood, sprouts of willow, roots of false indigo creep through the gravel, gripping, holding, and slowing the move. You might stay several decades or depart with the next big storm and move on again. Until you hit the jetty at Little Sodus Bay or get around it to move into the bay – and then stagnation.
I have long been fascinated by fossils. We have several types of fossils on the shores of Ontario. Some are casts or imprints left by hard bodied critters. I see these most often in a nondescript tan or brown rock that another beach comber recently identified looking like a burned brownie. Another type of fossil is the “trace” which represents some sort of activity by a creature a couple hundred million years ago.
Worm tunnels that appear as holes are fairly common. The most conspicuous fossils I have found are in gray limestone beach pebbles and are of various marine animals whose bodies became mineralized with calcium carbonate. The bigger fossil creatures sometimes show the crystals of this mineral quite clearly.
During the Ordovician Era, Lake Ontario’s watershed was covered by a warm sunlit shallow sea. At this time all of Earth’s larger, more complex creatures were marine life. Crinoids (sea lilies), corals, graptolites, snail like gastropods, clam like brachiopods, and a variety of cephalopods with shells – ancestors to today’s cuttlefish and nautoloids – along with other creatures, swarmed in the shallows. Evidence from the fossil record shows that an abrupt change in climate caused the second most severe mass extinction of this thriving community of life in Earth’s history.
About 440 million years ago, for some as yet unknown reason, the amount of CO2 in the atmosphere decreased. Earth’s climate cooled and a global ice age followed.
Cooling temperatures and falling sea levels caused by water being locked up as ice in vast glaciers then wiped out the vast majority of marine life. As we entered the Silurian age, marine life slowly began to recover. It took a few million years, but most of the fossils we see today in Lake Ontario beach pebbles are of extinct life forms.
Photos, from above: limestone pebble with marine cephalopod; assortment of metamorphic rocks transported by glacial action to south shore beach – these are gneiss and granitic pebbles from Canada and or the St.Lawrence thousand is area; ‘healed’ rock aka lucky rock of Lake Ontario; and typical gravel barrier bar on Lake Ontario’s south shore (Blind Sodus Bay).
Is it possible to find Tourquoise on the shore of Lake Ontario? I did. How is that possible?
J Burlew says
I believe it is indeed possible due to the travelling of plates etc I’ve also found some that are only native to Brazil and Africa on the southern shores as well. I’m literally addicted to the unique finds of lake Ontario. I’ll go out in THE crappiest weather just to find rarities (in my eyes) I have a literal storage unit full of rocks and have no idea what even 1% of them are but I have indeed found at least 5 good sized deep green turquoise. a gem stone cutter I met helped determine it was legit.
M Raff says
I will be visiting in late June staying lakeside near North Sandy Pond, northwest of Oswego. Can anyone share location tips for good rockhounding?
Thanks so very much in advance!
Lisa M Hamlin says
The Sandy Island Beach Park is right there. I have found many great rocks on the beach shores there. There is a website called Owlification and they give descriptions of Lake Ontario rocks.
Ted Cunningham sir says
I found 160 pound lake superior needle saganite