Dye tracing is a method used by hydrogeologists to trace the flow of underground streams and rivers. Join the Geological Survey of Northern Ireland and our Caves Team to watch the Owenbrean River turn an astonishing, luminous shade of green! Hear all about the hydrology and geology of the area surrounding the Marble Arch Caves, learn about the importance of dye tracing in the field of Geology and the various pieces of equipment used to carry out these exciting experiments.