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October 18, 2021     Post 131
What I learned from beach pebbles

If you crack under pressure healing is possible.

Illigitmi non corrundum my Dad used to say-Don’t let them grind you down. If you’re a beach pebble,though, sometimes taking the edge off results in smoother relationships.

Change is Inevitable so be open and prepared for it. It’s all part of a vast cycle as rocks become pebbles, gravel and then sand that then becomes rock again after 50 million years.

Go with the flow. As the water erodes bluff faces and waves push the pebbles along, they get to see new beaches all the time!

The following is adapted from a chapter contained in my book “A Natural History of Lake Ontario” now on sale in my Etsy shop. Find the link at susanpgateley.com upper right corner of homepage.

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 be reborn again as rock. This has been going on for about 4 billion years. The geologists call the process The Rock Cycle. Just as souls do in some religious beliefs, stones and boulders get reincarnated. 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.

I have described the Lake Ontario Lucky Rock as being ‘lucky’ to survive part of its journey through time. Lucky rocks are dark limestone 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 calcium carbonate then bathed it and over time, the mineral precipitated and bonded the two pieces of rock back together. Geologists call them ‘healed’ rocks.

South shore beaches are unusual. Thanks to glacier transport, the rocks and gravel came from many places to gather here. And the beach is a part of a ‘system’ that is more complex and dynamic than we imagine. Who knew the life of a beach 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 “overwash” and now you’re hanging out at the bar. 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 to move on again. Until you hit the jetty at Little Sodus Bay or get around it to move into the bay– then stagnation.

Early in my beach combing career I became fascinated by fossils. As I wrote in “A Natural History of Lake Ontario” there are several types of fossils on our shores. 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 as being “burned brownie rock”.(see below) Another type of fossil is the ‘trace’ fossil which simply 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. These show in the last photo with this story.

A few years ago I noticed several gray cobbles lying near one another on the beach each decorated with a mysterious dark spot outlined in rust. This was a great puzzle to me. How on earth did a piece of iron get embedded into what appeared to be a limestone rock. Had this water rounded stone once been part of a meteorite? Was this the result of some sort of industrial activity? Who would pound a piece of steel into a rock? I was flummoxed. Totally stumped. As time went on I found more of these rocks. But the mystery remained unsolved. Until one day while looking up information on fossils I learned about something called “pyrite rot”.

Pyrite (fool’s gold) is a common mineral often found in sedimentary rock. It is sometimes formed within the body of an organism as it becomes fossilized especially if the creature is associated with organic rich sediments. If the critter fossilizes in an anaerobic environment pyrite may form in or around it. In rare cases the entire creature’s substance maybe replaced by pyrite. The mineral is not real stable.

When eroded out of the ground and exposed to air and humidity it oxidizes and quickly changes to a rust like form. So, now I’m thinking maybe those mysterious “rusty” spots represent the remains of some slug of organic material or perhaps the body of some little critter that was once embedded in ancient marine mud. Maybe.

Like the professor told me when it comes to rocks your story is as good as anyone’s...

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