Whether sedimentary rocks store fossil hydrocarbons or act as impermeable layers to prevent the rise of oil, natural gas or ...

is generally greater on thick soil, although less porous soils, such as clay, act as impermeable layers. Urbanisation, with bare concrete and tarmac forming impermeable surfaces, creates a steep ...

Permeable and impermeable layers of rock in the Malham area give rise to intermittent drainage. We see features formed both at the surface and underground. Surface water passes over impermeable ...