This is an EARTHCACHE - so you are looking for information, not a
box. Since the site is a Site of Special Scientific Interest (SSSI)
it is important that you do not damage any plants of animals you
may see.
To log this earthcache you must send me the answers to
these five simple questions
Start
You will start at the lookout point at N 53 21.296 W 003 19.056.
This gives you information about the area.
A feature of many seaside locations is sand hills or sand dunes.
But how are dunes formed?
Made of Sand
The first thing to notice about these dunes is that - obviously
– they are made of sand. But what is sand made of?
Pick up a handful of sand. You will notice that it
consists of grains of many colours. The sand is finely ground up
materials from a number of sources.
- The bright white particles are calcium
carbonate coming from ground up sea shells
- The pale yellow, glassy, sparkling or dull white grains are
grains of feldspar or quartz often ground from
from granite rock. Quartz is also known as Silicon Dioxide, and is
used to make silicon chips for computers
- Black grains often come from basalt and other
volcanic rocks.
Question 1 Look carefully at your handful of
sand. Which is the commonest colour? So which is the most common
rock source of this sand? Shells, quartz or basalt?
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How does a dune get started?
For a dune to form, the grains of sand need to be light enough in
weight to be blown by the wind. As the wind blows over the beach
the grains dry out and they get carried along in low clouds of
airborne sand.
The sand blows across the beach until it hits an obstacle. It
could be a stone on the beach, a piece of driftwood or even a bit
of seaweed. When it hits the obstacle the sand falls, protected by
the shelter that the obstacle provides. One grain is joined by tens
of thousands and millions more till it forms a heap – a tail
of fallen sand on the leeward side of the stone.
The sand continues to pile up behind the obstacle in the
direction of the prevailing wind. One small heap joins to another
and the mound grows. If it rains on the heap, the rain is enough to
stop the wet sand blowing away. Heavy rain starts to fix the embryo
dune in place. The other crucial element to stabilise the new dune
is plant life, particularly the type of grass called marram grass.
This is the long grass growing all over these dunes. Hardy plants
like marram send roots into the loose sand, thereby helping to hold
it in place.
Question 2 What are two essential things for
dunes to get established?
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The Prevailing Wind Direction
The sand dunes are formed from two wind forces - the
prevailing wind and on-shore
winds. The prevailing wind blows loose sand along the
coast, then on-shore winds blow the loose sand inland to form the
sandhills.
Question 3 Stand at the highest point near
point N 53 21.347 W 003 19.265 You will see sand hills stretching
out in a long line. What is the direction of the sand dunes from
this point? North, East, South or West – use your GPS?
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Pebbles on the beach
Pebbles are thrown up by storms and high tides on a beach. If
you go to position N53 21.325 W003 19.282 you will see some
pebbles. Looking at positions of the the pebbles and the sand
dunes, answer this question.
Question 4 What do you think may have happened
for the pebbles to be in this position?
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How High
Finally use your GPS. Go to the top of the highest nearby sand hill
Question 5 What is your GPS reading of the
height of the highest sand dune above sea level.
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Log your visit with your answers using the "write note"
option. I will then give you the OK to log your cache.