GuidesMagazineShopBuy FossilsJoin Hunts
Elbert

Hello, your "C" scenario is indeed a simplyfied version of what I think happens; this is typical at locality`s where, at least a part of, the cliff is built up out of mudstone/clay.

As at Black Ven, it often happens in a sequence: with bad weather the cliff builds up water and then it slumps, sometimes multiple slumps follow each other.

When a slump happens in an old arc, the sea puls the debrisline towards the low water mark and merges the lines with each other.

It can also happen that the sea takes most of it away, as at Port Mulgrave(left), these things totally rely on the local conditions.

When Cliffs are made out of mostly limestone, like Burton Bradstock, I noticed, the image is not so clear.

greetings, Bert


the search is as valuable as the finds...
Quote 0 0
Dirty Pete
While sitting on top of Golden Cap the other day noticed these arcs of hard boulders at the base of the
cliff which must be the remnants of old cliff falls/slides.
IMG_0620_Copy.JPG 
I assume most of these boulders are fallen bits of the Three Tiers (see 3 prominent bands in cliff below)
3tiers_Copy.JPG 
Anybody know why the boulders concentrate at the periphery of the arcs?
Thanks
Pete.

Quote 0 0
Elbert

Hello, I think the boulders are pushed out by the weight of the clay/mud behind and end up just above the low watermarmark because they cannot get much lower; the clay will dissolve in the seawater, taking with it the weight of the mud.

A bit like a glacier, that pushes the morene in front...


greetings, Bert

the search is as valuable as the finds...
Quote 0 0
Dirty Pete
Thanks for that Bert.
I did some doodling (sorry for the ridiculous oversimplifications) and I guess your mechanism is
something like (C), where significant movement continues after the original collapse.
IMG_0657_Copy.JPG 
Some of the arcs seem quite extensive so assume they are built up from a number of smaller cliff
collapses/falls and do not represent one event. Is the arc shape therefore just a reflection of the shape of
the original cliff line or is there some other process/es going on?
Thanks
Pete




Quote 0 0


Discussions on fossils, fossil hunting, rocks, locations, and identifying your finds.
(C)opyright 2019 - UKGE Ltd and UK Fossils - Contact us