HolyHead Hill EarthCache
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Some of the oldest rocks in Britain can be found on Holy Head mountain and here Precambrian strata forms the islands highest point which is a Quartzite Formation that contains little groundwater
On the summit of the mountain is a prehistoric hill fort named Caer y twr and an area of 7 hectares is enclosed by a stone rampart.
The metamorphic rock quartzite is formed from sandstone or chert that has been heated and recrystallized during metamorphic episodes such as regional deformation or contact with molten rock. Exposed quartzite’s are resistant to weathering and commonly project as high hills and ridges.
Some of the textural features of the original sandstone or chert, such as the shape and size of the grains and the type of bedding, are retained. Quartzite derived from sandstone shows dust-like inclusions that can show the outlines of the original grains. Quartzite from impure sandstones (containing mica or feldspar) may grade into other metamorphic rocks, such as schist or gniess. A mosaic of small grains is typical of quartzite derived from chert. If the chert had altering thin layers of silica and shaley material, the quartzite typically preserves this feature. Quartzite formed during regional deformaion shows the pressure or stress of metamorphism in elongated and parallel quartz grains or in a preferred orientation of the crystallographic axes of quartz grains of any shape.
To log this cache please upload a photograph of you or your GPSr from the co-ordinate given with the quartzite rock
Also please answer the following
1) Estimate the size of the rocky outcrop of quartzite to the left of the hill
2) How many years ago where the rocks formed
Any logs with no photo will be deleted
Additional Hints
(No hints available.)