Nafferton is one of a line of villages that mark the boundary between the chalk of the Yorkshire Wolds, the northernmost chalk outcrop in Britain, and the clay of the Holderness plain. These villages are characterised by natural springs. At Nafferton there are allegedly seven springs that feed the mere - an artificial mill pool held level by a sluice and drained by Nafferton Beck. The water mill no longer exists, having been converted to steam in the 19th century and demolished in the 1980s, and the mere was sold to the parish council for one pound.
The coordinates take you to a brick contained karst spring next to the horse-wash. The level of the water inside the bricks is higher than the mere in an effort to prevent contamination.
The Yorkshire Wolds are an outcrop of Upper Cretaceous chalk - the remains of microscopic algae that fell to the bed of a tropical sea. Rain filters into the porous chalk but cannot pass through clay and other non-permeable rock on which it sits, so the chalk acts as a reservoir. As more water enters the chalk it is forced out through faults in the surrounding rock or at the lower edges of the chalk, and it comes to the surface as springs. The chalk reservoir regulates the amount of water supplied to the springs, and ensures that the temperature of the springwater is fairly stable all year. At Nafferton, the temperature of this spring is about 6 degrees Celsius (43 farenheit) and on cold winter mornings it can look as though steam is rising above the relatively warm mere.
Because chalk streams transport little suspended material they are described as 'gin clear', but this does not indicate that the water is fit to drink, although the trout like it. Don't drink from Nafferton spring or the Mere!
Springs are often classified by the volume of the water they discharge. The scale for spring flow is as follows:
Magnitude Flow (Litres/second)
1st magnitude 2800 L/s
2nd magnitude 280 to 2800 L/s
3rd magnitude 28 to 280 L/s
4th magnitude 6.3 to 28 L/s
5th magnitude 0.63 to 6.3 L/s
6th magnitude 63 to 630 mL/s
7th magnitude 8 to 63 mL/s
8th magnitude 8 mL/s
This Earthcache has been placed to coincide with International Earthcache Day 2015.
To claim the Earthcache at Nafferton mere you must answer the following questions about the site by messaging or emailing the CO, please don't include the answers in your log:
1. What is the approximate age of the Upper Cretaceous chalk through which this water filters?
2. Estimate the flow of the spring in millilitres per second at the published coordinates and state its magnitude using the table.(I measured the flow using a stopwatch on my GPS and an old plastic washing-up bowl and a measuring jug!)
You may also post a photo of yourself at the cache.
CONGRATULATIONS to the MGowners for the FTF, and to FASTRAC for the STF, both on International Earthcache Day 2015.