June 1998

Heather Sloan and Graham Stewart travel to Scotland with a team of mold-makers to make a cast of the famous Hutton Unconformity. In the 19th century, James Hutton, often called the "Father of Geology" used this outcrop in Siccar Point, Scotland as evidence of his notion of an "unconformity," or preserved gap in time, in the geologic record. Christened the Hutton Unconformity, this outcrop shows red sandstone over shales and reveals a gap of 20 million years in the sedimentary record. An unconformity usually results from a change from a depositional environment to an erosional environment.

A view of Siccar Point, Scotland, site of the Hutton Unconformity.

photo credit: Craig Chesek © American Museum of Natural History