Description:A photograph of a layers of rocks in Galway. There are two people in the photograph. The caption at the back of the photograph reads "During the later Carboniferous, about 300 million years ago, the seafloor in West Clare subsided. Black shales were deposited on a stagnant seafloor rather like the bed of the Black Sea today. Occasional beds of phosphate are packed with animals which once lived in the water column but after death sank to litter the seabed.".