Definition: Generate an appropriate title for the given text. The generated title must be short and include the main topic of the text. The preferred titles are under fifteen words.
Input: Tonnes of rock collapsed into the sea between Langdon Cliffs and South Foreland Lighthouse. Dover Coastguard said no-one was injured during the "substantial" rockfall, which happened in an area know locally as Crab Bay. The National Trust has put up warning signs to alert walkers. It is thought freezing conditions over the winter may have weakened the chalk cliffs. A full survey is expected to be carried out to determine the amount and length of cliff that collapsed on Friday. 'Crumble away' A spokesman for Dover Coastguard said: "We can see the start of it from where we are based but then it goes round the corner. "It appears that it crumbled from the top at high water so there was no-one down below at the time. It was quite a substantial fall. "No-one was injured but it does serve as a reminder that if people are walking along the cliff-top or underneath, that the cliff can crumble away. "Over the years and around the country, including along the coast at Beachy Head in East Sussex, cliffs can fall after water expands when there has been freezing conditions." In January 2011 several tonnes of rock and boulders broke away in St Margaret's Bay between Dover and Deal.

White cliffs of Dover section falls into sea