Transcript Slide 1

Holderness case study
The FASTEST
ERODING
COASTLINE in Europe
Locally, rates of erosion have been up to 10-20m per year
Holderness Coast is
fastest eroding
stretch of coastline in
Europe – an average
of 2 metres fall into
the North Sea each
year
Over 30
villages have
been lost since
Roman times,
erosion has
been taking
place for last
6000 yrs
http://news.bbc.co.uk/1/hi/uk/7390654.stm
The Holderness Coast is one of Europe's fastest
eroding coastlines. The average annual rate of
erosion is around 2 metres per year. This is
around 2 million tonnes of material every year.
Under lying the Holderness Coast is bedrock
made up of Cretaceous Chalk. However, in most
place this is covered by glacial till deposited over
18,000 years ago. It is this soft boulder clay that
is being rapidly eroded.
But what is the obvious question
/ learning objective???
WHY
is it eroding so
quickly?
KEY REASON: it’s made of boulder clay – the most easily erodeable ‘rock’ (it’s not really a rock as it was deposited by the ice sheets
in the last glaciation and has never then been buried and
compressed and ‘turned to rock’ like chalk, sandstone, etc have)
Notice the slumping... (subaerial process,
happens on ‘soft rock’ coasts
Less Resistant bolder clay cliffs near Mappleton
Landslips: also known as rotational slumps, are occasional
rapid movements of a mass of earth or rock dropping down
along a concave plane. Water percolating through sandstone
gets into the clay beneath, saturating it. With the weight of the
rock above forcing down on it the clay moves seawards as a
mud flow. With the clay moving sideways the sandstone above
slumps down. Undercutting of a steep slope by the sea
weakens the rock above, making a slump more likely.
13
Relatively long FETCH –
dominant wind direction = from
North East – so large waves
Mappleton, Yorks.
coast
Groynes
£10,000 each (wooden groynes)
£1.5m each (rock groynes)
What are they designed to
do?
Stop longshore drift
Further down the coast this
may mean that beaches are
starved of sand and shingle
Click here for video clip of Mappleton – where they built the rock groyne (£2m) to prevent
prevent longshore
longshore
drift – but
drift
causing
– but causing
more erosion
more further
erosiondown
further
thedown
coastthe
– eg
coast
Cowden
– eg Farm (Sue
Cowden
Earle)
– as
Farm
the(Sue
beach
Earle)
there
– stopped
as the beach
getting
there
‘fed’stopped
with sand
getting
and ‘fed’
shingle
with
from
sand
further
and North...
shingle from further North...
Mappleton and Holderness Coast
Why???
Describe the effects of the erosion here.
What would the knock on effects be? (classic 6-marker)
So, over to you…
Holderness: The FASTEST ERODING COASTLINE in Europe
(1) Add labels to the map &/or photo to explain why it is eroding so quickly. Include at least these:
cliffs = boulder clay,
longshore drift,
groyne,
long fetch,
North Sea,
Mappleton village,
thin beach
(2) On A4 paper, try to write a sentence for each label explaining how it helps cause rapid erosion
EXTENSION: Draw a spider diagram giving reasons why people still live on this coastline