The geology of Ivybridge is varied. Throughout most of the town the rock is Old Red Sandstone (correction:this should read ‘heat-altered slates), (sedimentary) from the Devonian period. To the north of the town Granite can be found as it is situated on the slopes of Dartmoor – a large pre-volcanic area of Granite. Along the River Erme large boulders and rocks can be found deposited on its meandering path brought all the way from Dartmoor; the Ivy Bridge itself is made out of Granite.