Thousands of tons of boulder clay crashed off the cliffs near Whitby's ancient Abbey - just four days after a previous landslide.
Fortunately the collapse happened at night - in daylight, the fall could have killed a team of council engineers working at the base of the cliff.
John Riby, Scarborough Council's Principal Engineer, said "It landed on the spot where we are currently carrying out sea defence work.
"Had it happened during the day when there were workers on site there could have been a major disaster."
The latest fall affected cliffs near the Abbey headland car park, where there is glacial boulder clay. He blamed the recent heavy rain and cold nights for the slippage.
As a result, some ten metres of the land broke away along a 20 metre stretch, taking with it a fence erected only four days previously, following a landslide of some 6,000 tonnes.
Now the council, which owns the cliffs, has brought in contractors to carry out investigations.
English Heritage officers have been informed because of the threat to archaeological remains on the abbey headland.
Emergency warning signs have been erected on the cliff tops to tell the public to keep away.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article