Bonhay Road cutting is one of the best and easiest places in the UK to view the Crackington formation and is considered to be important because of the fossils that exist within the rock. The same rocks can be seen from North Cornwall all the way to Germany and were formed in deep waters many millions of years ago. The site is a Site of Special Scientific interest (SSSI) and is jointly managed by Exeter City Council and Natural England.
Look at the exposed rock face and you will see bands of shale, sandstone and siltstone. These rocks were formed at the bottom of the ocean in deep waters during the Carboniferous Period. Subsequent movement of the continental plates has exerted huge pressures on the rock causing it to fold and crumple. This is why you can see many faults at GZ.
Once you have been to the site please send me a message with answers to the following questions:
- Look at the exposed rock either side of the retaining wall and you will see the layers are running in two different directions. Describe the two alignments of the rock strata.
- Identify which type of rock you think constitutes the thickest layer. Is it the sandstone, siltstone or shale?
- How many millions of years have passed since these rocks were formed?
- Have a look at the site, assess its condition and send me a few words with your thoughts on this.
I like seeing your photos on my cache listings but this is entirely optional. If you do wish to post a photo of you and/or your GPS at the site please don't post images of the interpretation board! Feel free to log your visit at the same time as sending me the answers.