Approaching Worsaw Hill
The white rocks you can see emerging out of the ground here are limestone and were formed over 300 million years ago. Making up the foundations of Pendle Hill, limestone is very common in the Yorkshire Dales and across the Craven Basin. During the time of its formation, a period of time known as the Lower Carboniferous period, Britain was positioned just 14 degrees south of the equator and was inundated with warm, tropical seas, allowing an abundance of calcium-rich marine life, such as coral and ancient shelled equivalents to clams and mussels to thrive.
Over time, this marine life would die and their calcium rich shells and bones broken down by waves. The result of this would then be compressed and hardened by the sea and land above to form layers, or strata, of limestone (otherwise known as calcium carbonate).
Such a layer of limestone is visible above Downham and the Hookcliffe plantation, where a protruding step can be seen before the rising summit (pictured below).
Evidence of such life that provided the calcium-rich material neccassary for the creation of limestone is widely visible throughout limestone in the form of fossils, where animal remains have resisted wave erosion and intead been preserved in the rock. Fossils are imporant as they can tell us what life was like millions of years ago, helping us to understand the geology and climate of the time. In limestone, fossils are often darker than the surrounding stone and are textured as the harder parts of their skeleton protrude from the rock. Here, there are fossils of crinoids and coral, being filter-feeding animals found on the ancient sea-bed. Whilst classed as animals however, crinoids and coral amost resemble plants and appear ribbed (see picture below).
Where such calcium rich life has continued to grow rather than die and fall to the sea floor however, dramatic cones of coral reef formed and have remained a conical shape even once transformed in to limestone. This is the case of Worsaw Hill, where this EarthCache is located, giving it Site of Special Scientific Importance status as a 'reef knoll', and a listed biological heritage site due to the specific plants that grow around limestone due to the calcareous (alkali) nature of surrounding soil. This is again due to alkali properties of the rock reducing acidic qualities in poor soils making them more tolerable to plants.
(Crinoid fossil preserved in the limestone at Worsaw Hill)
To claim this EarthCache, please submit your answers to the following questions using the message feature above. Alternatively, please send your answers to the email address included in my profile information.
- Touch the limestone with your hand and describe the physical composition of the rock. Hints: Is the overall texture of the rock smooth or rough? Are there other types of rock present within the limestone? Look for grains in the rock and estimate their size.
- Look at the beds of limestone in front of you. Estimate the angle they exist at relative to the ground.
- Find a fossil in the limestone and submit a photograph of you or a personal item with it.