Warden Point is the clearest example of land erosion in Kent.
The whole of the Isle of Sheppey is built on London Clay, which is
about 47-48m years old or slightly older. The upper reaches of the
clay are fairly solid due to the presence of shingle - small rock
and pebbles that predominate the natural beaches in the area, and
provide good consistency for building foundations to be firm.
However at Warden point you can see how deep the shingle levels go
- or rather how shallow.
Strata of clay
To the east and west of here you should be able to find sections of
the cliffs that are very vertical, and some that are 'slumped' to a
gradual incline. Look for a vertical stretch showing large sections
of 'clean' mud (clay) and soil in the vertical cliffs. You should
be able to see three layers (see image gallery for help) - the top
soil, a short layer that contains shingle - small stones, pebbles,
etc - and that this stops after a while and makes way for older,
purer (wetter) London Clay.
Question 1: How deep does the shingle section go?
Be sure to only look at the vertical cliffs sections - the cliffs
slump down in places, you don't want to look at those parts. A
rough numerical estimate is fine.
In any case, you'll see that the shingle does not penetrate far
down. The softer clay underneath is fine as long as it does not get
wet - for example does not get rained on! But here at Warden Point
it is very exposed to the wet northerly weather and when wet, the
purer (lower) clay will turn into a very soft goo - and ooze down,
trying to find a natural 30º slope.
Question 2:In which direction can you find the vertical
cliffs ('scarps' in the diagram): East or West? Bonus points if you
can work out why (look for 'somethings' that protect the vertical
cliff faces).
Despite these 'somethings' that explain why the cliffs are
partially more protected in one direction than the other,
eventually both sides (and the bit you are standing on) will
inevitably fall in, due to the erosion that the sea causes in
addition to the weather. The "toes" in the diagram above are
mini-cliffs in their own right, and are eaten away by the actions
of the waves and tide. Spend a moment to ponder on the
inevitability of cliff erosion - if you are interested in how to
stop this long-term, visit the nearby Minster Cliffs, which have
had a massive programme of defence, and may be a great site for a
future Earthcache of their own! I seriously doubt if Warden will
ever receive that level of investment, or protection.
The town of Warden
If you have left the road, return to it now - this is now the 'end
of the road', but it never used to be that way. The village of
Warden stretched out about half a mile or further from here on
older maps - see the gallery for some pictures of the buildings
that have gone over the cliffs, and note as you stand here that you
can still see some WW2 block houses clinging to the lower cliffs.
Just a few houses remain behind you, but at low tide as you look
out over the mud flats you may still see the lines of where the
streets and their houses have slumped into the sea over the years.
In fact you are standing right beside where the Post Office was a
little as 20 years ago - incidentally it used to be the Smack
Aground Inn, an alleged hiding place of the North
Kent Gang and various local wreckers over the years. The
building has since been demolished on health and safety grounds.
Note that the buildings of the town probably accelerated the demise
of the cliffs - they failed to protect the steep cliffs when they
went over (not tall enough), and their weight would drag the cliffs
down all the faster, unlike the objects seen back in question
2.
Question 3: At the geocache coordinates you will find a
large signpost warning you of the cliffs (big red oval with the
word 'DANGER' in it). To prove you are actually here, who erected
the signpost?
eMail your answers to EARTH@sharant.com. Anyone not
sending in answers may have their logs deleted.
Optional Task: When you post your log, use the 'coordinates'
feature to record the furthest piece of road that it is safe to
stand on. Be sensible here - emphasis on safe
Additional Photo Task
Without endangering yourself or people with you, take a photo at
any point along this cliff showing the cliff in the background and
your GPS unit in shot. Hopefully over time the gallery will
become a nice record of the area's ever-changing features.
If you are interested in learning more about cliff erosion, we
found this
website to be particularly clear (and we borrowed our nice
diagram from it as well).
Also nearby you can find the remains of a WW1 Sound Mirror -
look here to learn more about that, and to see some old aerial
photos of the area.