Low tide at the sunken forest of Borth

Photo: Kristi Herbert/Flickr

Those aren't shark fins or broken teeth sticking out of the water. This surreal landscape shows the remains of a prehistoric sunken forest that was buried under the shore of Cardigan Bay thousands of years ago.

Stretching intermittently over two or three miles between the towns of Ynsy-la and Borth, the eroded tree stumps and fossilized peat are most visible during the winter, when rough storms have a tendency to rip up and expose the British coast.

So how did this ominous sunken forest come to be?

Petrified tree stumps on the beach of Borth

Photo: yrhenwr/Flickr

The forest, which contains a mix of oak, pine, birch and alder trees, gradually became engulfed by a peat bog during the Bronze Age — sometime between 4,500 and 6,000 years ago. That peat bog was then swallowed up by the surf over the next several thousand years.

The wood has remained remarkably well-preserved because the peat's high alkalinity and low levels of oxygen neutralize hungry microbes.

Local folklore suggests the forest is the mythical kingdom of Cantre'r Gwaelod, which is often described as the "Welsh Atlantis." According to one variation on the legend, the sunken kingdom was lost beneath the waves after a maiden named Mererid let her well overflow.

Medieval walkway in Borth

Photo: Wikimedia

Along with petrified tree stumps and fossilized peat beds, the storms recently uncovered the remnants of an ancient wooden walkway (above). Dating back to 3,000 to 4,000 years ago, it was constructed using logs and branches to help the ancient Welsh locals navigate the soggy ground as the sea levels continued to rise around them.

Borth's beach

Photo: Chris Denny/Geograph

The area around Borth isn't the only place where harsh storms perform expert archaeological excavation work. A particularly violent storm in 2013 revealed the Jurassic-era remains of an ichthyosaurus along a beach in Dorset.
Fossilized tree stump

Photo: Wikimedia

The skeletal-like remains of an old tree are seen buried in sand and petrified peat.

Fossilized peat on Borth beach

Photo: Penny Mayes/Geograph

Hard, lumpy peat deposits rise out of small tidal pools.
Petrified tree stump

Photo: Wikimedia

Tree rings are still visible in this eroded stump sticking out of the water.

Sunken forest at sunset

Photo: Wikimedia

The sun sets on the petrified tree stumps of Borth's beaches.

Petrified tree stumps with stones

Photo: Wikimedia

Water and smooth stones fill the crags of an ancient tree stump.

Borth's petrified forest beach

Photo: Wikimedia

A petrified tree stump juts out of the textured beach sand.

Peat walkway

Photo: Wikimedia

Large lumps of fossilized peat stretches out into the surf.

Ancient wood in Borth

Photo: Penny Mayes/Geograph

Ancient chunks of wood and fossilized peat stick out of the beach sand.

Fossilized peat in Borth

Photo: Wikimedia

A large chunk of peat bog pools in the sand.

Borth peat

Photo: Wikimedia

Tiny holes drilled by molluscs gives this fossilized peat a porous look.

Fossilized peat on Borth beach

Photo: Penny Mayes/Geograph

The remains of the peat bog stretch out over the beach.

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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.