Durham Dales: High Force
High Force is England’s biggest waterfall and drops 70 feet (21m) into the plunge pool below.
The upper rock is the Whin Sill dolerite said to have been formed 295m years ago (magma formed a sheet known as a sill).
The lower rocks are sandstone and limestone at the base, which are less resistant to erosion and get worn away by the force of the water. As the more resistant dolerite is undercut it becomes unstable and collapses leaving behind the angular collapsed rocks and boulders.
At the foot of the waterfall is a deep plunge pool. The waterfall has been developing for over 10,000 years. A steep-sided gorge has developed as the waterfall has retreated upstream.
www.northpennines.org.uk/publications/high-force-and-bowl...
This GCSE BBC resource is about the River Tees and uses High Force as an example of a waterfall. Please note rocks should be described as less or more resistant not 'hard' or 'soft'.
www.bbc.co.uk/bitesize/guides/ztpkqty/revision/4
The waterfall is within the North Pennines Area of Outstanding Natural Beauty and European Geopark.
Durham Dales: High Force
High Force is England’s biggest waterfall and drops 70 feet (21m) into the plunge pool below.
The upper rock is the Whin Sill dolerite said to have been formed 295m years ago (magma formed a sheet known as a sill).
The lower rocks are sandstone and limestone at the base, which are less resistant to erosion and get worn away by the force of the water. As the more resistant dolerite is undercut it becomes unstable and collapses leaving behind the angular collapsed rocks and boulders.
At the foot of the waterfall is a deep plunge pool. The waterfall has been developing for over 10,000 years. A steep-sided gorge has developed as the waterfall has retreated upstream.
www.northpennines.org.uk/publications/high-force-and-bowl...
This GCSE BBC resource is about the River Tees and uses High Force as an example of a waterfall. Please note rocks should be described as less or more resistant not 'hard' or 'soft'.
www.bbc.co.uk/bitesize/guides/ztpkqty/revision/4
The waterfall is within the North Pennines Area of Outstanding Natural Beauty and European Geopark.