Glacial striations

As you approach Austwick Beck and its Clapper bridges along the walled lane you will notice that you are walking on solid rock. Looking carefully at this rock will reveal great scratches made by the passage of glacial ice. They are called striations and indicate the direction of ice flow.

Unconformity

It is possible to make a detour from the standard Crummackdale phototrail route in order to view and examine the junction between the ancient Silurian rock strata and the Carboniferous limestone laid on top. The geological term for this is an unconformity. After crossing Austwick Beck at the Whitestone Lane Clapper bridge follow the lane a short distance to a junction and turn left. Walk about 200 metres North on this lane until you reach a sharp right-angled bend in the track. Stop here and look up to the cliff to the East of your position.

The sea floor on which the Carboniferous limestone sediments were deposited was once an ancient land surface, heavily eroded over millions of years. About 330 million years ago, and following a change in climate, the land was covered by a warm, shallow sea. Calcareous remains of sea life were deposited on the sea floor over a prolonged period of time, building up layer upon layer until they completely covered the ancient folded landscape.

Looking up at the cliff you can see the almost horizontal bedded limestone resting on the tipped up and folded rocks beneath. The lower rocks are the Silurian greywackes tipped almost on end and cut off by erosion. The locals call the lower rocks Horton Flags. These Silurian rocks are very hard wearing and shear off in great slabs. Over the past few hundred years they have been quarried and used for roofing flags, paving stones, cowbyre partitions, grave stones, clapper bridges etc. Today the stone is used for road chippings

Underground drainage

From where you view the unconformity you can also see the course of an ancient waterfall on Studrigg Scar. It is usually dry but during wet weather water may be seen running over it. The normal drainage in limestone areas is underground, with streams emerging where the water meets with the Silurian rocks. You can see evidence of this in the many small springs or resurgences all the way along the foot of this scar.