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 →


Faces of Extinction 3

When mass extinctions occur, as they have five times previously in Earth's history, every member of a given species expires. Not just the old, the infirm, those who have a certain vulnerability. All members of the species die, even the babies. After spotting dozens of limestone skulls of extinct creatures on Lake Michigan's Left Coast,... 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 →

Faces of Extinction 1

As children we wondered, "Why don't we see living dinosaurs?" "Because they are extinct," a parent or teacher told us. And we learned that "extinct" is an adjective meaning "of a species, family, or other larger group having no living members." ( We might further learn such facts as: "Species become extinct for many reasons,... Continue Reading →

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