Significance: the largest known glacial erratic in Scotland
Beside Kidlaw Farm (509642) is a hill formed in a mass of shattered Carboniferous Limestone. The bedrock here is Old Red Sandstone so this is a glacially-transported bedrock raft, the largest known glacial erratic in Scotland. The limestone was formerly quarred and the old lime kilns and quarry works are still clearly visible.
The site abuts the rising ground of Lammermuirs. The ground here is deeply corrugated by meltwater channels and bedrock is often buried by thick accumulations of sand and gravel, as shown by the gravel workings nearby at Long Yester. The adjacent hill has a large kame terrace on its flank.
The source of the limestone probably lies a few km to the NW. The giant erratic belongs to the Carboniferous Lower Limestone Group of East Lothian, and it has been carried at least 2 km from the main outcrop of this rock, which lies to the west. Rising ground beneath thin ice sheets favours the detachment of glacial rafts.