These islands are accessible on foot for approximately 6 hours a day during low water. The walk is between 4 and 5 miles in total for the return jouney. For information regarding this please see the various websites or noticeboards at West Kirby. DO NOT attempt to cross before reading the various information. There is a distinct route which must be followed and tide times to be adhered to.
You should now be standing on the jetty of the old lifeboat station on Hilbre Island.
Earth Science Lesson on Coastal Erosion
The biggest factor affecting coastal erosion is the strength of the waves breaking along the coastline. A waves strength is controlled by its fetch and the wind speed. Longer fetches & stronger winds create bigger, more powerful waves that have more erosive power.
As waves approach a coastline they lose energy though because friction with the seabed increases. This means that the bathymetry (the underwater elevation) of the ocean or sea bed also impacts on the strength of waves.
Certain landforms further reduce wave erosive power. Beaches increase the distance a wave travels before it reaches the coastline cliffs and so reduces its energy. Headlands refract waves around them, reducing their erosive power at one location while increasing it at another. Weathering also plays a role in the rate of erosion by creating weaknesses in rocks that are exploited by the processes of erosion. Freeze-thaw weathering, for example, creates cracks in rocks, increasing the rock susceptibility to hydraulic action.
As always, humans have an impact on coastal erosion. Human activities have a variety of complex effects on coastal erosion but most commonly the activities increase the strength of waves. One activity, dredging, is commonly carried out to improve shipping capacities but it reduces the amount of energy dissipated from incoming waves and so increases erosion.
In order to log this EarthCache please answer the following questions :-
1. When looking eastwards from the jetty (right hand side as you face downhill) there are a large number of rocks close by, please state the approximate dimensions and shape of the rocks.
2. Where do you think these rocks came from ?
3. State approximately how many of these rocks you can see is it a few, tens, or hundreds ?
4. Do you think that they used to form part of another structure ? if so what ?
5. How do you think the rocks were moved from their original placement ?
6. Are the rocks retaining their original shape, and has anything become attached to them ?
7. A photo showing the inside of the station NOT the rocks would be nice and even better if it included yourself or GPS.
Please submit your answers via the MESSAGE system which allows a photo to be attached. Any photos containing information about the EarthCache posted on the page will be deleted. Thank You.