Lowest tide of the year reveals remains of ancient submerged Cornish forest in Mount's Bay

A tree trunk rises above the water, and which is believed to be between 4,000 and 6,000 years old. Credit: BPM Media.

The lowest tide of the year in Cornwall has revealed an ancient submerged forest believed to date back thousands of years.

Winter storms shifted sands in Mount's Bay, meaning when the sea withdrew further than usual, the remnants of prehistoric trees trunks, stumps and roots became visible.The submerged forest in Mount’s Bay has been known about for centuries, and St Michael’s Mount’s original name in Cornish is ‘Karrek Loos yn Koos’, which means ‘Grey Rock in the Wood.’

But the peat beds that contain the remains of what was once an ancient forest are only revealed when there are extremely low tides and when sand has shifted.

An ancient tree stump sits among the sea weed - this is only the fourth time it has been visible in a decade. Credit: BPM Media.

More than a year ago, lots of signs of the ancient forest were seen in January following storms on the south coast.

The ancient forest could also be seen in March 2021 during the biggest tide of the year. But the prehistoric stumps at Chyandour beach in Mount’s Bay had not been visible before that since February 2014.

The lowest tide of 2024 for Mount's Bay happened on Tuesday 12 March, when sea levels dropped to just 0.22 metres at Newlyn.

Flood warnings were issued by the Environment Agency for the same day covering most of the north coast of Cornwall, because of the extreme high tides.Using radiocarbon dating on the peat beds at the time geologists concluded that extensive forests extended across Mount’s Bay between 4,000 and 6,000 years ago.

Cornwall Geoconservation Group, who monitor the state of the ancient submerged forest in Mount's Bay, believe there are a number of similar submerged forests around Cornwall that are occasionally revealed from under the sand, including at Bude, Daymer Bay, Portreath and Pendower.

A prehistoric log thought to have stood between four and six thousand years ago emerges from the sands. Credit: BPM Media.
The area where there is a concentration of ancient forest stumps is at Chyandour, to the east of Penzance, and west of St Michael's Mount. Credit: BPM Media.
The stumps became visible after the lowest tide of the year, where sea levels dropped to 0.22 metres. Credit: BPM Media
What appears to be a pine cone in the layer of peat. Credit: BPM Media
There are several other submerged forests around Cornwall, including at Bude, Daymer Bay, Portreath and Pendower. Credit: BPM Media.
The tree trunks, stumps and roots sit on peaty soil within the sand, within an exposed rocky area which is around 50 metres wide. Credit: BPM Media.