Around 350 million years ago the Peak District was covered with a shallow tropical sea. This area being a living lagoon, Over millions of years, the remains of shellfish and other sea creatures were compressed into what we now call limestone. The fossilised sea creatures such as crinoids or brachiopods can be seen clearly in the rock...
..In a tropical sea around 350 million years ago: the geologists' "Carboniferous" period. In seas that were warm and free of silt, the hard parts of (mostly microscopic) invertebrates built up on the sea bed and formed a limey mud. Something similar can be found in the Caribbean today. Normally the shells and skeletons decayed and fell into microscopic pieces, but occasionally waves or current buried a complete animal, and, lost to the processes of destruction & decay, they reappear today as fossils - usually crinoids, but occasionally trilobites and shellfish. A wide variety of minerals were deposited in cracks and cavities in the limestone after it had formed, but whilst it was still deeply buried. Lead and fluorspar are the most economically valuable of these minerals.
Below is a guide as to what happened from the period starting 350 million years ago onwards to 1 million years ago (working backwards):
Geological History - Time Line
Years Ago:
1 Million
A series of Ice Ages begin, separated by periods with a climate similar to that of today. In early glaciations, the Peak was covered by ice hundreds, perhaps thousands, of feet thick - like modern Greenland. The ice front of the last Ice Age came no further south than Leeds andt he Peak underwent a period of intense, dry cold: tundra. As the deeply frozen surface layers thawed at the end of the last ice age, landslips were released and boulders slipped downhill on buried ice layers.
60 Million
Area uplifted out of the sea. The rock layers which had accumulated over the previous 200 million years begins to erode away, eventually leaving the landscape we see today.
280 - 60 Million
Derbyshire at or below sea level. Long periods of deep submergence left at least a kilometre of rock above the Gritstone. Minerals, including lead, dissolved in groundwater (often under pressure and at high temperatures), were deposited in faults and caverns.
280 Million
Tropical swamps, occasionally flooded by the sea. The drowned soils became fireclays, tree ferns became coal. Britain started to drift slowly north, part of a global shuffling of land masses.
300 Million
Derbyshire was in the delta of an immense river which dumped sand and mud over much of what is now England. Sorted by currents and tides, the muds deposited in deeper water became shales, and the sands gritstone.
350 Million
Britain was far from it's current position, south of the equator. Derbyshire was covered by clear, warm seas, teeming with life. Limey muds and the hard parts sea creatures built up on the bottom, Limestone formed from these sediments.
Here in the Castleton region, the underlying limestone is gently dipping, poorly fossiliferous with some coral bands. The (amygdoloidal) basalt within these beds is exposed in Cave Dale and has been correlated with the Lower Lava of Millers Dale.
More about Cave Dale itself:
Cave Dale (sometimes spelt Cavedale) is a dry limestone valley in the Derbyshire Peak District, England. The northern end of the dale starts at the village of Castleton where the valley sides are almost perpendicular. The dale rises gently after leaving Castleton for approximately 200 metres before becoming steeper culminating in fine viewpoint down the dale taking in Peveril Castle with Lose Hill behind. After the viewpoint the dale swings west and levels out with gentle gradients, becoming just a shallow depression as it peters out onto the open pastureland between Castleton and Chapel-en-le-Frith.
Cave Dale was initially formed by glacial meltwater carving a deep narrow valley in the local soluble limestone. The river then found a route underground leaving a dry valley with caverns underneath. Later on the caverns below Cave Dale collapsed making the valley even deeper and gorge-like at the northern end. The Castleton entrance to Cave Dale had a narrow natural arch as recently as 200 years ago, a relic of the roof collapse. The lower slopes of the dale have large amounts of scree, frost on the higher limestone cliffs having caused the rock to shatter. Halfway up the valley is an outcrop of basaltic lava with a few small columns. A bridleway runs the entire length of the dale, part of the Limestone Way footpath.
The chambers and caves of Peak Cavern run directly below Cave Dale and any small streams in the dale quickly disappear into the ground down limestone fissures and into the caverns beneath. Mineral veins can also be seen within the limestone of the dale. The cliffs at the northern end of Cave Dale are used by rock climbers and there are several routes in the Very Severe category. There are several small caves or old lead mines within the dale's limestone walls, with one being larger than the rest with bars preventing access. Cave Dale's steep north-facing grassy slopes are damp and bryophyte-rich and are dominated by oat grass (Trisetum flavescent) and Sheep's Fescue (Festuca ovina). Lesser meadow-rue (Thalictrum minus) grows extensively on ledges in the dale.
At the southwestern extremity of the dale as it merges into the moorland between Castleton and Peak Forest are the remains of several old lead mines.
At the entrance to Cavedale at the start of the public footpath, can be found an information board with lots more information on the area, the area is truly amazing and well worth walking all the way through past the published coordinates you will need to go a little further to find the lava.
TO CLAIM THIS EARTH CACHE:
Please post a photo of you or your GPS with the limestone valley face in the background.
2. Please email me the approx height of the almost perpendicular limestone valley walls (in feet or meters - whichever you use)
3. Photograph an example of the basaltic lava, halfway up the valley.
Any logs without the logging requirements may be deleted.
PLEASE NOTE: I receive a very high number of Earthcache emails, I can’t reply to them all otherwise I’d be doing nothing else all day, as has always been the case there is no need to await a reply from me regarding your answers…. However due to numerous people thinking they can just log these caches without emailing any answers, and/or completing the required tasks these will be picked up, and the logs will be deleted without further communication. To facilitate this Please email your information either before, or AT THE SAME TIME OF LOGGING THE CACHE, Thanks.