The Drinking Dragon or Durdle Door shows a great example of erosion.
In this EarthCache I'm going to try and keep it simple as I find I get lost and confused with EC's at times.
Erosion, whit's the crack?
So, looking at Durdle Door you will notice there's a big massive hole in it.
Erosion is responsible for this.
There are various types of erosion.
Hydraulic action - the sheer force of water crashing against the coastline causing material to be dislodged and carried away by the sea.
Abrasion - when rocks and other materials carried by the sea are picked up by strong waves and thrown against the coastline causing more material to be broken off and carried away by the sea.
Attrition - when material such as rocks and stones carried by waves hit and knock against each other wearing them down.
Solution - when sea water dissolves certain types of rocks.
This big hole has been formed because the rock itself is made up from different types, some of which are softer than others eg. limestone and chalk stone
The sea water batters the rock and the softer rock crumbles and erodes, forming the arch.
At the same time the arch is being formed, the sea is also hitting the beach and slowly eroding that, but that's also doing something else...as the waves smoosh in and out they carry pebbles, rocks and shells which then wear more of the rocks away, which, in turn, creates more beach and erodes the cliffs.
As recently as 2013 there was a large rockfall by Durdle Door which closed the long distance path there.
To log this EarthCache can you answer the below;
1. Estimate the height and width of the arch?
2. What types of erosion are creating the arch?
3. How long until the arch collapses?
4.What type of rock is Durdle Door made from?
4. OPTIONAL TASKS: Can you create, with all the pebbles around you, or draw in the sand, what the arch will look like once eroded? And, whilst not mandatory, take a pic of you, your cache locating device or something with your cache name on it at Durdle Door.
EarthCache placed with kind permission of the owner.
