Hutton's Unconformity, near Lochranza, Arran

At this locality, Precambrian rocks are dipping to the left, while the overlying Carboniferous rock are dipping to the right. The lecturer is pointing out the unconformity between the two horizons - which in this case represents a time gap of over 250 million years.

Follow this link to see a drawing of another famous unconformity described by Hutton; this other Hutton's unconformity, at Siccar Point in the Borders of Scotlands, is illustrated here.

DSC03013: GBCurry