SLOPE FAILURE TYPES:

Scree

scree

SLOPE FAILURE NAME:

Scree

DEFINITION:

Sloping mass of loose rocks at the base of a cliff.

MAIN CHARACTERISTICS:

Screes extend on the foot of rocky cliffs, and they are overwhelmingly built by Middle Basalt stones that fall from that cliff due to block release or toppling. Toppling based screes have larger boulders than those that are formed by block release. There is also a sorting downslope by rock size whereby larger particles can fall till the foot of scree, while small sized particles remain oat the top. This provokes that vegetation growth from top to bottom.

Screes are conditionally stable at the Giant’s Causeway, and due to their stability they are being colonised by vegetation. However there are some active screes whose profiles are over the equilibrium point (usually situated around 35º), because they are still being fed from cliff rockfalls.

Most of the screes, only found in bays, are possibly inherited from the last previous high sea level and stand above the raised shore platform. If sea level rises and storm surge height increases, there is a potential for screes to be re-activated by marine undercutting of toeslope.

CAUSES:

Rockfalls (block release and topple) feed screes, so they are originated by the same causes than rockfalls.

AREAS PRONE TO FAILURE:

There are screes on the foot of well developed rocky cliffs, mainly in Port Ganny area.

OCCURRENCE:

Screes are continuously forming, based on block releases and toppling.

up


Home  | People  | www.qub.ac.uk | www.uva.es | www.nationaltrust.org.uk |