More than 4,000 tonnes of rock have fallen on a beach popular with holidaymakers from around the UK.
It is the biggest rockfall in 60 years on the stretch of the Jurassic Coast in Dorset as boulders the size of cars crashed 430ft to the ground.
Luckily no-one was injured but Dorset Council is urging people to stay away from the area and the damage is being assessed.
It affected almost 1,000ft of cliffside, with whole trees seen floating out to sea, and is being linked to natural erosion, not helped by the recent mix of weather.
Jake Lanning, from West Bay Coastguard, told the Daily Mail: "It is a very very substantial fall.
"The county council are aware of it and I know their rangers have been out assessing the damage.
"I believe it was caused by substantial cracks around the cliff, which have occurred as part of natural erosion.
"The recent warm days and cold nights probably haven't helped either and we're expecting to see a fair bit of this in the coming weeks.
"In terms of this one, high tides will eventually see the debris disappear but at the moment the beach is completely cut off.
"We weren't called out to it, as there is not any danger to life, but we did get a lot of calls about debris in the water."
'The fall was so big that people thought the rocks and trees were vessels and/or people in difficulty.'
