Landslips near Lyme Regis

On this page: Somewhat away from the virtual pasture, I have been taking an interest in local coastal landslips starting in the winter of 2000-2001.

February 2001: The local press was full of reports of big rock falls, the coast path had to be diverted east of Lyme, the 16th hole of the golf course is increasingly precipitous, and every so often, the coastal rescue helicopter buzzes up and down the Undercliff looking for possible casualties - though with 100 tonnes of rock on your head, with little point!.

Why so many in Winter 2000-2001?

There was an unprecedented amount of winter rain in the period (at least unprecedented in the last 300 years or so). The landslips occur when water saturates the soft shales, which become greasy and allow the harder limestones to ski over them and down onto the beach, taking trees, grass, and shrubs with them.

My friend John Wood has link to external site local rainfall statistics that show just how wet it has been.

Slips at Monmouth Beach, Lyme

Every winter, there are some rock falls on Monmouth Beach (just west of Lyme), but recently they have been both more frequent and voluminous. These pictures show just a couple of examples:

There are three separate falls shown at the left. Above each, you can see a brownish streak, probably left by the soil that follows the underlying (grey) rocks down the face.

The one on the right had only just happened when I took the photo on the 18th February - there were still lumps of soft shale on the limestone terrace that hadn't been washed away by the sea. The big block of limestone in the foreground (which must weigh well over a tonne) bounced about 30 metres across the terrace - yet there were families bashing at the cliffs with hammers quite oblivious to the danger, even though showers of debris were coming down the cliff at regular intervals.

photo of mud flow taken at Lyme in early January 2001Not all the slips are of hard debris. There is a lot of water running down the cliffs, and in the right circumstances, the shales can turn to a thick plastic mud, which flows down and across the sand (see right). Every year, at least one walker has to be released from a mud flow by the emergency services, having ignored the warning notices.

photo of boulder with possible slickensides<- This boulder (the one in the foreground above right) is from a limestone bed (unusually thick at about 1m) near the top of the cliff. The joint planes are scored with striations - I would call them slickensides if this was a fault plane, which of course it might well be. Or they may have occurred as the block slid down past its neighbour.

Update: Summer 2001

There was a pretty huge volume of falls in the spring, despite a fairly long dry period before the rain set in again. Almost a continuous slope of debris developed along the stretch of cliffs shown above left. I haven't ventured to the beach recently - too many people about! But not so many slips, I think.

Slips at Cain's Folly, Charmouth

photo of landslips east of Charmouth, DorsetJust before the New Year 2001, there was a really massive landslip east of Charmouth, the next coastal settlement east of Lyme. Unfortunately, the two days we visited were both dull and misty, so you can't see a lot in the photo. If you are familiar with this scene, you will appreciate just how much of the cliff has come away - you can just see shallow cones of debris reaching into the sea left of Golden Cap - under the arrow.

I'm afraid we laughed at the orange barrier with the "beach closed" sign, which seemed a rather futile defence against the fossil-hunters clambering all over the base of the slips. But I guess the local authority has to protect itself against people who do reckless things and then try to sue it for their own stupidity!