The rocks seen at Joppa were laid down as horizontal layers, approximately 300 to 320 million years ago in the Carboniferous Period. They have since been tilted to the east by tectonic forces. This rocky shore represents millions of years of sedimentation and is why the site is included in the Firth of Forth Site of Special Scientific Interest.
At this time, Scotland sat close to the Equator experiencing warm tropical conditions. The rocks demonstrate that this was a low lying coastal area which experienced repeated cycles of subsidence and uplift. This resulted in many different environments and the formation of a variety of rock types from the deposition of river-borne sand, shallow marine limestone, deltaic sediments, lagoonal mud and much more, including swamp forests and their soils.
One important environment, recognised over different sites, was the lycopod forests (similar to mangrove swamps present in the world today) and is the source of the Scottish Coal Measures Group.