Camulodunum Protected! EarthCache
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Grymes Dyke earthwork is off the junction of Dugard Avenue and Peartree Road in Colchester. There is residential parking close by. The track can be very muddy after rain so probably not suitable for wheelchairs.
.·:*¨¨*:·. FTF – kevanjue .·:*¨¨*:·.
The purpose of this earthcache is to obtain some insight into the way our Iron Age ancestors protected their territory against aggression from neighbouring tribes. As well as this earthcache's historical nature, it is also aimed at discovering the effect those ancestors had on the landscape and geography of their surroundings, and to show something of the geology of the area that these defences were constructed on.
Much like the rest of North East Essex, the Colchester area has been formed by a number of geological episodes over the past 60 million years. It has been beneath a tropical sea, under hundreds of metres of ice and rivers, and glaciers have shaped the landscape.
The age of the rocks in the Colchester area are relatively young in geological terms. Laid down around 55 million years ago, the geology of the area consists mainly of London Clay with some Upper Chalk. There are also superficial deposits of semi-pervious Boulder Clay, sands and gravels.
Deeper down, there are ancient Palaeozoic rocks, movement along a fault of which, affecting the overlying Cretaceous and Tertiary strata, may have caused the famously destructive Colchester earthquake in 1884, supposedly the strongest tremor in recent British history. Although felt as far away as France and Belgium, as well as a considerable part of southern Britain, it is known as the Colchester earthquake because the town seems to have been the epicentre of the tremor, as most of the structural damage appeared to occur in the Colchester and Wivenhoe area.
Built and shaped on this geological foundation, the Lexden earthworks form just part of a series of defences, created in the late Iron Age, that protected the western side of pre-Roman Camulodunum (modern-day Colchester). Camulodunum was the capital of both the Trinovantes and Catuvellauni tribes, and was ruled over by Cunobelin (Shakespeare's Cymbeline).
The Gryme's Dyke, which forms the basis of this earthcache, is probably the most recent of the dyke system, being post-Roman conquest in date.
Camulodunum, covering an area of about 12 miles, was defended in the north, south and east by the river Colne and the Roman River, and the Lexden earthworks are part of the 15 mile system of defences that comprised the western boundary between the rivers. Most of the dykes were composed of a V-shaped ditch and a bank that was built from the tons of earth that were removed from the ditch.
There was some variation in the depth of the ditches, from dyke to dyke, from around 5 feet deep to around 13 feet deep. The banks could be up to 10 feet high, making a barrier of up to 25 feet. This would be of particular use against chariot attack.
The defences are thought to have been constructed in the early first century CE, but later added to post-Roman invasion and possibly even post-Boudican.
To claim this earthcache you will need to perform five tasks:
1. Estimate the height of the bank from the bottom of the ditch as it is now at N51˚52.863 E000˚50.970
2. Estimate the height of the bank from the bottom of the ditch as it is now at N51˚53.053 E000˚50.905
3. Estimate the height of the bank from the bottom of the ditch as it is now at N51˚53.091 E000˚50.889
4. Estimate the length of this section of the earthworks from the start point to the large wooden gate
5. Take a picture of yourself and your gpsr with the bank of the earthwork in the background
PLEASE NOTE: If you take one of the high paths, the drop is quite steep and the path quite narrow, so please be careful.
Email the answers to tasks one to four to me at gt@geotrowel.com at the same time as you log your find. Please post your picture with your log.
That's about it, hope you enjoy this earthcache!
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