In 1869 a one-armed self-taught geologist led an expedition party down Green River in Wyoming. While staring up at the great walls of the Grand Canyon John Wesley-Powell noticed that the rock formations were less in-depth than expected.
By measuring the depth of the rock formations Powell noticed something startling - there was more than a billion-year gap in the geological record.
This was coined ‘The Great Unconformity’’ and now geologists are racing to track down this apparent gap in time.
To discuss, Jonathan is joined by Rebecca Flowers, Associate Professor in the Department of Geological Sciences at the University of Colorado, Boulder.