This is an EarthCache, there is no physical container. In order to log a find please visit the site, read the text and e-mail me through my profile the answers to the questions and activities in bold at the end of the description. You can log your visit straightaway, if there are any problems I will contact you and if there is anything you're not sure about please get in touch and please add a photo to your log from your visit.
Farthing Downs is part of the North Downs chalk ridge which stretches from Farnham in Surrey to the famous white cliffs of Dover in Kent. It was one of my favourite outings to come here when I was little and we still love visiting and usually drive this way home if we've come through Caterham.
Farthing Downs and New Hill is a 95 hectare area of chalk grassland with areas of scrub, ancient woodland and hedgerows.It is owned and managed by the City of London and along with Happy Valley to the south is an SSSI supporting a wide variety of flora and fauna.
This area has also been a prominent area for human activity with archaeological finds dating from neolithic,iron age and roman times and is a SAM - scheduled ancient monument. Many thanks to the Natural Environment Division of the City of London corporation for permission to place this EarthCache.
Hopefully this EarthCache will give you a feel for the immensity of the landform from which the relatively gentle south-east landscape has evolved and the chalk that forms this distinctive region.
The chalk of the Downs originally formed during the Upper Cretaceous period in a relatively deep marine environment.Microscopic skeletons of plankton would sink to the seabed becoming lime mud and under increasing pressure transform into the characteristic white rock that is evident today. This appearance is due to the colourlessness of the skeletons and lack of impurities in the original environment.
Rock formed in shallower waters may include mineral deposits and biological 'debris' during formation adding colour depending on the conditions at the time.
Chalk is a very permeable rock which allows water to percolate through rather than collecting on or flowing over the surface making it particularly resistant to erosion. It also means that at deeper levels extensive aquifers can form as chalk can store a huge volume of water.
As the environment changed during geological periods of time the deposition of different materials transformed into distinct rock types and these layers or strata would have been essentially horizontal.
Around 20 million years ago tectonic activity (movement and changes in the earths crust) caused these rock layers to fold and lift forming a huge anticline (a dome-like structure) in the regions that are now south east England and part of northern France.
Subsequent weathering and erosion again over vast periods of time wore away the upper layers and the raised areas of rock and the North and South Downs are the remaining edges of the dome where the more resilient chalk forms the distinctive ridges we see today.
Due to the angle of the rock layers and subsequent erosion there are two very different landscapes on the north and south sides of the each ridge.
Looking north towards London from GZ is the corresponding syncline known as the London Basin and the land that slopes gently down to this is called the dip slope. The valleys and hills either side(east and west) of GZ have been created by 'smaller' scale geological activity.
If you were to look south from the North Downs over the lower lying area between here and the South Downs known as the Weald ( from Caterham Hill, for example, a short drive away but not essential for this Earthcache, ) there would be a steep scarp slope dropping away from you.
The diagram shows an extremely simplified and exagerated cross section of an anticline where the bold blue line represents the current landscape and the patterned areas the underlying folded strata.The dashed lines represent where those folded strata would have continued prior to erosion.
QUESTIONS AND ACTIVITIES
1/ At GZ are you standing on part of the original anticline or syncline?
1a/ What is the elevation at GZ as recorded on the cairn?
2/ Farthing Downs is largely grassy but at Waypoint 2 there is an area of exposed chalk. What do you think has caused this patch? Please briefly describe the chalk you can see here, eg. size and shape of pieces, colour, texture.
2a/ Given your observations from the previous question would you conclude that the hardness of chalk is what makes it so resistant to erosion.
3/ At the waypoint, ( you do not need to be at the exact location ) in the far distance and weather permitting you can see London city. Scan to your right and you may see the Crystal Palace transmitting mast and then Croydon. Between GZ and Croydon you should be able to see a distinct chalk feature. Do you think this has occurred naturally or is it manmade and how does it compare to the profile of the landscape of Farthing Downs?
4/ Please include a photo of your visit either with yourself or pertinent item without giving any of the answers away.
TAKING CARE
Although there is now a 20mph speed limit along Ditches Lane some vehicles still travel very fast and along the open stretch of road it can remain very icy in winter even when surrounding roads are clear.
In summer months there may be cattle roaming but they are very docile and accustomed to walkers.
The terrain setting for this EarthCache is based on having driven to the listed car park, for which there is unfortunately now a charge but please don't park along Ditches Lane. 1 hour is probably enough but you may want to spend more time to enjoy the area. You can usually park at Chaldon Church for a longer but reasonably level walk.