Learning Objectives
- To understand the geology of the 'crag walk' and how it is different from the native geology of the area.
- To be able to consider how the land forms are being changed by the crag walk; and how the land would be different if the craig walk had not been built.
Background Information
The crag walk was built in Walton on the Naze in 2011 to slow the rate of coastal erosion. It involved 1,600 tonnes of granite being placed at the base of the cliff to slow erosion; the total cost was £1.2 million. The co-ordinates for this cache are at the start of the walk. To complete this cache you will need to walk the length of the crag walk (100m).
Positioned up to 4m from the base of the cliff the construction comprises of a base foundation slab forming the toe of the structure keyed into the beach; retaining a 4m deep, 13m high revetment formed from 5 - 9 tonne natural rocks that provides the foundations for the public access platform. There are information boards along the crag walk - reading the information boards will provide more information about the crag walk - and help you answer the questions.
The design of the walk can absorb wave energy and allow incoming tidal water to percolate through the structure and present a sustainable, low maintenance structure of natural materials that will reduce erosion by the sea to a minimum. A large placement of rocks at the far end of the wall will protect the platform from outflanking.
Tasks
The majority of the answers can be obtained from looking at the information panels that have been placed on the crag walk.
1. How long is the crag walk? (measure it with your GPS)
2. What is the average weight of each rock?
3. What rock type is the crag walk?
4. What is the rock type of the cliffs? Why do the cliffs erode so quickly? Describe how the physical appearance of the rocks that make up the cliffs is different to the rocks that make up the crag walk.
5. Where did the rocks come from? How were they brought to the area?
6. Using the rate of erosion posted and an estimation - how long would it be before the tower ended in the sea if the crag walk had not been built.
When you log the cache please also email or message the answers to me - however you don't need to wait for a response before logging.
Agreement for this cache has been given by Tendering District Council