quarry

Myers’ vision for the area included reintroducing animals that had once been native inhabitants, including tule elk and bighorn sheep, and obliterating man-made intrusions, such as a rock quarry, petroleum waste pits, fences and roads.

Graphite at the Zavallya quarry is processed at the sprawling refinery site a short distance from the canyon.

This summer, more than 100 scientists, students and volunteers joined an excavation at the quarry which features on the new series of Digging for Britain.

Pete Burgess, of the Wealden Cave and Mines Society, said a quarry marked "sand pit" can be seen on 19th century maps of land directly under the sinkhole.

In July, police arrested Collins Jumaisi Khalusha, who they described as a "serial killer", after the mutilated bodies of nine women were found in a disused quarry.