Welcome to Ilkley Moor! This cache is one of a series of caches that will take you on a tour of some of the many geological features that you can find at this scenic location.
Ilkley Moor
Ilkley Moor is an area of upland moorland, covering 676 hectares. Internationally, this type of moorland is rare, despite being relatively common in the North of England, and as a result has significant nature conservation interest. Mosaics of heather moorland, blanket bog, acid grassland and flowing streams make up the character of Ilkley Moor. Mixed with these are small stands of pine woodland, scattered trees, tarns and exposed rock faces.
Ilkley Moor is underlain by a succession of shale and course grained sandstones including the Addingham Edge Grit that forms the Cow and Calf rocks. The sand that forms these rocks was originally laid down on shifting sandbanks in a great river about 320 million years ago during the Carboniferous Period.
Deep burial caused the sand to harden into rock and subsequent earth movements and erosion brought the rock back to the surface again. By the end of the Ice Age, about 13,000 years ago, ice had scoured the moor and deposited the long low ridge of Lanshaw Delves, a glacial moraine. Since then peat has accumulated in sphagnum bogs.
Particulate and Wind Erosion
When you continue along the path to here you will notice that the path becomes formed of loose sand, or other small particulate. This loose sand is the result of weathering and erosion over time, caused by aeolian processes (processes caused by the actions of the wind).
Wind erodes the Earth's surface by deflation (the removal of loose, fine-grained particles by the turbulent action of the wind) and by abrasion (the wearing down of surfaces by the grinding action and sandblasting by windborne particles). Particles are transported by winds through suspension, saltation (skipping or bouncing) and creeping (rolling or sliding) along the ground. Saltation is downwind movement of particles in a series of jumps or skips. Saltation normally lifts sand-size particles no more than one centimeter in diameter above the ground and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains that jump up to continue the saltation. The grain may also hit larger grains that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains.
A 1998 study published in Earth Surfaces Processes and Landforms investigated the relationship between vegetative cover on sand surfaces with the rate of sand transport. It was found that sand transportation by the wind, as explained above, decreased greatly with vegetation cover. This was done by measuring plots of land with varying degrees of vegetation against rates of sand transport. The authors contend that this relationship can be utilized to manipulate rates of sediment movement by introducing vegetation in an area or to quantify human impact by recognizing vegetation loss’s effect on sandy landscapes.
Logging your Find
In order to log your find, please send a message to my profile answering the below questions. The answers can be found by visiting the location, reading the above description, and taking observations in the field. You'll need a measuring tool (for example, a small ruler marked in millimetres) for this one.
Look at the path.
- Go to three different locations along the path, each at least 3m apart. Measure three samples at each location, and compare the overall average grain size, to tell me what is the average size of the grains making up the sand on the path?
- Describe how you think the size of the grains is linked to how likely these are to be affected by aeolian processes.
- Explain how our impact on the landscape, including the creation of the path, could increase erosive forces on Ilkley Moor.
As Ilkley Moor is a stunning part of the world, you may optionally want to upload photos of your visit, of course I would love to see them! I will respond to your message as soon as I can.