Explore the geology and history of Sidmouth's coastline. Learn about the Otter Sandstone, the 1824 storm, and the changing mouth of the River Sid.
The coastline surrounding Sidmouth is a three-mile stretch of dramatic cliffs and shifting sands, running from High Peak in the west to Salcombe Mouth in the east. This area offers a unique window into the Earth's past, featuring Triassic "red beds" and evidence of thousands of years of coastal change.
At the western edge of the bay, the landscape is defined by the Otter Sandstone, which has been carved by the sea into a series of striking sea stacks.
Peak Hill Geology: The cliffs here consist of Mercia Mudstone, which grows thicker toward Peak Hill.
The Lost Chit Rocks: Offshore, you can see the Chit Rocks. These are the remnants of a massive, 40-foot-high formation of Otter Sandstone that was famously destroyed during a severe storm on November 22, 1824.
Marine Life: At low tide, the base of these cliffs reveals rock pools that support a variety of local marine life.
The town of Sidmouth is nestled in the valley of the River Sid, flanked on both sides by towering cliff faces.
The Esplanade: This iconic walkway sits atop a historic shingle ridge, a remnant of what was once known as the "Great Beach".
The Rock Islands: In 1994, as part of a coastal protection scheme, two "islands" were built offshore using 90,000 tonnes of granite and larvikite to shield the town from erosion.
Jacob’s Ladder to Connaught Gardens: While much of the beach is shingle , a man-made walkway protected by granite boulders runs east from Jacob’s Ladder. Past Connaught Gardens, an extensive area of sand is exposed during low tide.
The eastern end of the Esplanade marks the mouth of the River Sid. This area is a dynamic environment where the river and sea are in constant "tug-of-war".
A Shifting River Mouth: High tides push sediment into the river, while low tides allow the river to erode that sediment away to reclaim its path. After heavy storms, shingle barriers can cause the river to back up significantly.
The Sidmouth Tunnel: Near the Alma Footbridge, visitors can see a breached opening in the cliff. This is a remnant of the 19th-century Sidmouth Tunnel, a railway system that was once buried deep behind the cliff face but has since been exposed by coastal erosion
The cliffs to the east, including Pennington Point and Salcombe Hill, are primarily composed of Mercia Mudstone topped with Upper Greensand.
Feature Geological Composition
Cliff Base Mercia Mudstone & Otter Sandstone
Hill Tops Upper Greensand & Clay-with-Flints
Beach Sediment Dominated by Flint and Chert
The eastern section, particularly East Beach, is closed to the public. This is due to:
Frequent Rock Falls: Erosion is common, making the cliff base highly unstable.
Tidal Cut-off: At high tide, the sea reaches the base of the cliffs, leaving no escape route for walkers.