Slip or Slump
Valentines Day Massacre?
St Bees Coast 2011
Coastal Features
• Tomlin Head faces the West
• The Golf Course cliffs faces the west
• Between these a bay faces southwards and so takes the full force of the wind and waves
• Tomlin Head is made from younger Red sandstone
• The Golf course is made from loose debris
Slip or Slide?
SLOW
Carson = Kirkby
WET
DRY
FAST
Creep Slide
Slump
Obviously not a slow creep as the movement was rapid [overnight]
But was it a slip [dry]? or slump [wet]?
Notice the rounded ‘toe’
Notice the shapes [there were two movements]
Easternmost
Area of erosion
Mov
emen
t
toe
Cone shaped top
Westernmost
Can you identify the two distinct zones?
Why are they different colours?
Colour
Light
WET
DRY
Light
To the left you can see how saturated this is – 100 mm of rain has fallen in
the last two weeks
This makes it – Heavier, Lubricated, and created a junction – the shear plane
From the top you can see the two ‘toes’
Putting all of the evidence together-
SLOW
Carson = Kirkby
WET
DRY
FAST
Creep Slide
Slump
1. Saturated soil
2. Concave erosion and convex shape
3. Easily identifiable ‘toe’
So, the footpath is closed