The listed coordinates for this EarthCache take you to Prebends bridge and a breath taking view point where you can see the beautiful river Wear flowing north through the city making a text book 'incised meander' enclosing the Castle and Cathedral on three sides to form the city peninsula. Twisting sinuously the river has cut deeply into the "Cathedral Sandstone" bedrock and a few coal seams are still visible in the banks today.
What is a Meander?
A meander is a river with lots of curves or turns. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the inside. The result is a snaking pattern as the stream meanders back and forth.
What is an 'Incised Meander'?
An incised meander is a river meander that has been cut abnormally deep into the landscape. Incised Meanders are created by the Rejuvenation of the river. Rejuvenation occurs when there is either a fall in sea level relative to the land or a rise of land relative to the sea. This enables the river to renew its capacity to erode as its potential energy is increased. The river adjusts to its new base level and in doing so creates the incised meander.
What causes this relative rise or fall of the land and sea which leads to river Rejuvenation?
Rejuvenation can be caused by a number of different factors.
1.Tectonic changes – Earthquakes can cause uplift along fault lines to create fault scarps several metres high. If this crosses a river, a waterfall will form and the river will begin eroding vertically at this point.
2.Fall in sea level caused by eustatic changes – during a glacial period, water is stored on land as ice so the sea level changes at a global level.
3.Fall in sea level caused by isostatic changes – after a period of glaciation the land will start to rise in response to the loss of the weight of the ice melting. This is called isostatic recovery or glacial rebound and occurs at a more local level.
4.River capture – over time rivers cut backwards at their source. This is headward erosion. Occasionally, as a river cuts back it can break into an adjacent valley and capture the tributaries of nearby rivers. There is usually a height difference at the point of capture and a waterfall is formed. This is a knick-point.
There are 2 types of Incised Meanders: Entrenched Meanders and Ingrown Meanders.
Entrenched meanders are symmetrical and form when the river down cuts quickly. The speed of the river down cutting gives less opportunity for lateral erosion thus giving them steep symmetrical slopes on both sides. The entrenched meanders of the San Juan River, Utah are a classic example.
Click here for link to a sister EarthCache in Utah for more information 
Ingrown Meanders are asymmetrical. They form when the river down cuts at a slower rate, allowing the river to erode laterally and vertically. The valley becomes asymmetrical with steep cliffs on the outer bends and more gentle slip off slopes on the inner bends. Tintern Abbey, the River Wye is good UK example.
The incised meander gave a natural access to the Middle Coal Measure strata dating back 300 million years ago from the Carboniferous age, the reminants of which can still be seen today. Coal was worked for centuries from several seams throughout the Durham coalfield. On the west side of the bridge slightly up the bank you will see a useful information board. Walk a short way uphill along the lane and find the 'old thinner seam at the foot of the small crag' referred to on the information board,(directly opposite a road drain). Walk on up further and find the sealed archway of the old drift mine.
To log this EarthCache please email me or reply through the message centre answers to the following
1.From GZ observe the river bank on the inner bend and look at the height of the bridge to the water level. Would you describe it as a fairly steep slope or a very flat slip off slope
2.Would you say the Incised Meander is Entrenched or Ingrown?
3.Explain in your own words the difference between eustatic and isostatic changes
4.What advantages were there for early settlers building the Castle on the peninsula created by the Incised Meander?
5.What 2 words are written to the left of the arrow sign on the drain by the thinner seam at the foot of the crag?
6.What are the 2 numbers on the yellow fire hydrant sign pinned on the entrance to the sealed mine?
7.Optional but desirable, please upload a photo of your GPS at GZ or take a selfie