A 400-million-year-old coral reef standing 75 feet over the Wabash
Four acres on the south bank of the Wabash near Lagro, made a National Natural Landmark in May 1986, and what it protects is a coral reef. Silurian, roughly 400 million years old, and exposed naturally rather than quarried into view: the limestone rises 75 feet straight out of the river, which is steadily undercutting it. A reef in Indiana is a reminder of how much of North America used to be warm shallow sea.
Other places on the map within a couple of hours.
