Bays and Headlands
A headland is an area of resistant rock that extends from the coastline into the sea. A bay is an inlet of the sea where the land curves inwards.
A headland is a cliff that sticks out into the sea and is surrounded by water on three sides. Headlands are formed from hard rock, that is more resistant to erosion, such as limestone, chalk and granite.
Headlands form along discordant coastlines where bands of soft and hard rock outcrop at a right angle to the coastline (see image below). Due to the different nature of rock erosion occurs at different rates. Less resistant rock (e.g. boulder clay) erodes more rapidly than more resistant rock (e.g. chalk).
The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland. The areas where the soft rock has eroded away, next to the headland, are called bays. Sandy beaches are often found the sheltered bays where waves lose energy, and their capacity to transport material decreases resulting in material being deposited.
The image below shows Selwicks Bay at Flamborough.
Where the geology alternates between strata (bands) of soft and hard rock are called discordant coastlines. A concordant coastline is where the same rock runs along the length of the coast. Concordant coastlines tend to have fewer bays and headlands.
Along the coastline of Dorset, there are concordant and discordant coastlines. The concordant coastline runs from west to east along the south coast. The discordant coastline runs from Studland Bay to Durlston Head as the geology changes from clay and sands, to chalk, to clay and sands again to limestone.
Use the images below to explore related GeoTopics.