This is an EarthCache. To claim a find you must complete the three logging tasks listed below. And remember to enjoy the view!
When standing on top of Worcestershire Beacon, at 425m above sea level, you are on the highest point of the Malvern Hills and the highest summit in Worcestershire. You are standing on Precambrian igneous rocks formed deep underground over 680 million years ago. To the south around Herefordshire Beacon there are younger Precambrian rocks formed by an undersea volcano about 566 million years ago. The hills immediately to the west are Silurian limestones formed between 428-419 million years ago. To the north, beyond North Hill, are Triassic sandstones formed 245-228 million years ago. And to the east is the Worcester Basin with Pleistocene to Holocene sediments that continue to be shaped today by the River Severn.
Underlying the geologically recent sediments filling the Severn Valley to the east is a rift valley, i.e. a very big hole in the ground, caused over 300 million years ago by massive earthquakes along the East Malvern Fault. Helpfully, the East Malvern Fault here is located roughly along the eastern edge of the Malvern Hills so it's comparatively easy to visualise. And what you should be visualising is the rocks that now form the Malvern Hills being thrust upwards by earthquakes, while the rocks underlying the Worcester Basin sank downwards. In fact, geologists hypothesise the downthrown rocks are as much as 3km below the current land surface, and the whole rift structure may be as wide as 25km (from the Malvern Hills to what is now Inkberrow). Faults can be complex structures but the diagram below will help you visualise what happened, as the "horst" block of the Malvern Hills thrust upwards and the "graben" structure of the Worcester Basin slipped downwards.
Fortunately the East Malvern Fault Complex is much less active now and the notable 4.8 magnitude quake in Dudley in 2002 caused more surprise than damage.
Three Logging Tasks
Please send the answers to Questions 1 and 2 privately to the cache owner, via the message link at the top of this page. Please post the required photo on your public log. Thank you.
Question 1. On the summit of Worcestershire Beacon are you on a horst or a graben?
Question 2. Looking east at the Worcester Basin (Severn Valley) are you looking towards a horst or a graben?
Task 3. Post on your log a photo of yourself, your caching mascot or name, with the toposcope or trig pillar on top of Worcestershire Beacon as proof of site visit.
And remember to enjoy the view!
Ye Ole Survey Monument is a series of caches in homage to OutForTheHunt's YSM series (GC45CC). YOSM caches are positioned at or near triangulation points, also known as trig points, which had a pivotal role in surveying and mapping. More information at the YOSM website:
https://yosm.org.uk