St. Michael’s RC School The Upper Course of a River

St. Michael’s RC School Processes of river erosion Hydraulic action Abrasion Attrition Corrosion

St. Michael’s RC School Abrasion/Corrasion This is the process by which the bed and banks are worn down by the river’s load. The river throws these particles against the bed and banks, sometimes at high velocity. Hydraulic Action This process involves the force of water against the bed and banks. Corrosion This is the chemical action of river water. The acids in the water slowly dissolve the bed and the banks. Attrition Material (the load) carried by the river bump into each other and so are smoothed and broken down into smaller particles. Processes of river erosion

St. Michael’s RC School Source of a River

St. Michael’s RC School river disappears from view hidden by this spur of land Upper Valley - River Conwy (near Mignant Moor) Landforms in the upper course V-shaped valleys and interlocking spurs Rapids Waterfalls

St. Michael’s RC School V-shaped valleys on OS map

St. Michael’s RC School Upper Course of River Tees

St. Michael’s RC School Waterfalls!

St. Michael’s RC School Waterfall formation

St. Michael’s RC School The waterfall retreats back forming a gorge (steep sided valley) Overhang becomes unsupported and falls into the plunge pool

St. Michael’s RC School High Force

St. Michael’s RC School

An example of a waterfall – Gulfoss, Iceland

St. Michael’s RC School Gulfoss is located in Southwest Iceland on the Huita River. Gulfoss has two ‘steps’ to its waterfall. These steps are made by basalt lava while the rocks between these layers are softer, sedimentary rocks. Its gorge is 70m deep and 3 km long! Gulfoss