Time & Deep Time

Want to study history? In American schools, most intro histories start with homo sapiens, us, and the European variety of us. But Earth's history is far longer. To get a sense of the scale of Earth history, imagine walking back in time, 100 years per step—every pace equal to more than three human generations. A... Continue Reading →


Extinction is Forever

Lake Michigan's Left Coast reveals Paleozoic limestone and dolomite dating to the Devonian Period (420–350 million years ago). Abundant in rocks from the Paleozoic are fossilized brachiopods, marine animals with upper and lower hard shells hinged at the rear. Though they first appear in rocks dating to the early Cambrian Period (540–485 million years ago), brachiopods reached... Continue Reading →

Straight-Bodied Cephalopod

On Lake Michigan's Left Coast in Wisconsin, thousands of ghostly images appear in the millions of rocks on the beach. They are mostly highly eroded, nearly unrecognizable fossils. Imagine my surprise when, one day, this hunk of limestone appeared, incredibly clear, fossil side up. I was astonished. This fossil impression, with its distinctive parallel ridges,... Continue Reading →


Chert is a sedimentary rock made almost entirely of quartz crystals. In the Great Lakes region of North America, chert forms as veins in limestone or as layers between other sedimentary rocks. Chert is very hard, so any fossils that formed in or of chert may be less eroded than those softer rock, like limestone.... Continue Reading →

Pipe Organ Coral Fossil

From the beach at Lake Michigan's Left Coast Pipe organ coral fossil, probably from the Devonian Period (419.2–358.9 million years ago), by Left Coast Creative (© 2017 Elizabeth G Fagan) for the blog Lake Michigan's Left Coast More about Left Coast Creative services & the blog Lake Michigan's Left Coast

Lake Michigan at 20-Year High

The Devonian Period (419.2–358.9 million years ago) jawless fish Cardipeltis has been found in Utah and Wyoming. This fossil is from Lake Michigan's Left Coast in the Great Lakes region. Is it the jawless fish? A hunk of fossilized mud? Along this beach in southeastern Wisconsin, Lake Michigan has been eating away at beaches at... Continue Reading →

An Odd Little Creature 1

This rock is unusual on Lake Michigan's Left Coast. It appears to be an odd little creature. The limestone bedrock at here is Devonian in origin, having been laid down some 419.2 to 358.9 million years ago, so maybe it dates from that period. Directly to the north and south, bedrock is a little older,... Continue Reading →

Faces of Extinction 2

Over its 4.6 billion-year history, Earth has changed many times, in many ways. Homo sapiens, the name we give ourselves, evolved a few million years ago, a tiny point in time when Earth's conditions were just so. A peculiar trait of a certain subgroup of Homo sapiens, aka humans, put itself at the center of... Continue Reading →

Tiny Brachiopod Shards

Very small shards of brachiopod shells appear in this jumble of fossils set in sandstone. Also visible are coral fossils. Copyright, Disclaimer, Glossary, Bibliography

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