gcse geography coastal land forms part one in this video we're going to look at discordant and concordant coastlines headlands and bays and caves arches and stacks watch part two for wave cut platforms beaches spits bars and sand dunes but let's get on with this video so rock types and geological structures influence the erosional landforms that develop on a coastline discordant coastlines are made of altering bands of hard and soft rock at right angles to the coast concordant coastlines have altering bands of rock that are parallel to the coast headlands and bays form along discordant coastlines they form when there are altering bands of resistant and less resistant rock along a coast the less resistant rock is eroded faster forming a bay with a gentle slope since the resistant rock erodes more slowly it juts out forming a headland with steep sides headlands create caves stacks and stumps the resistant rock that makes up headlands often has weaknesses like cracks waves crash into the headlands and enlarge these cracks mainly by hydraulic power and abrasion repeated erosion and enlargement of the cracks causes a cave to form continued erosion deepens the cave until it breaks through the headland to form an arch erosion continues to wear away the rock supporting the arch until eventually it collapses this forms a stack an isolated rock that's separate from the headland [Music] you