Daily Archives: 8 January 2016

Granite Falls

Old Rock

Along the Minnesota River, just past Granite Falls, and next door to the Yellow Medicine County Historical Museum, is (was) the world’s oldest exposed rock. At 3.8 billion years old, the rock was exposed when Glacial Lake Agassiz emptied into the ocean during the last Ice Age.

Some zircon crystals from the Jack Hills in Australia have recently been dated at 4.4 billion years old.