Can You Find a…Glacial Erratic?

A glacial erratic is a rock resting on today’s land surface that has been deposited by the retreat of glacial ice at the end of the last Ice Age 11.000 years ago!  Glacial erratics differ in size, shape and type of rock native to the area in which it rests. Erratics have been transported, sometimes hundreds of miles, by glaciers and can range in size from pebbles to enormous boulders. Here in Connecticut glacial erratics are often rock types which are most commonly found in northern New England and Canada.

  • Erratics are always different kinds of rock than the underlying local rock found in the area
  • Erratics are often well rounded with smooth surfaces
  • Sometimes erratics show scrap marks or striations where they ground against the bedrock or other rocks as they were moved along by the glacier.

Good examples of large glacial erratics can be found in the Medlyn section of the Hoadley Creek Preserve and in the Weil Preserve.

Submitted by Joan Merrick