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Terry James Walker

The Fossils that Millions of People have Walked Past

Fossils on the Summit of Mount Snowdon

A few pictures and brief explanation of the fossils to be found on the top of Snowdonia and Wales' highest peak

I head up to the summit of Snowdon throughout the summer months in charge of walking groups and climbing clients. These visits for me are very enjoyably on almost every occasion, only in the very worst weather (click here for trip that involved lightning) is it not an absolute pleasure to be paid to take people up this peak.

I find with most groups, the people are very interested in my knowledge and stories about the local rare flowers and descriptions of their historic medicinal purposes. The local birds and facts about each of them (e.g. The Skylark, I may see 20 on a single trip, can sing at 95 decibels.  To not deafen itself, when it opens its mouth to sing, its eardrum is stretched and hence protected from damage). Unfortunately, sometimes I get caught up working with groups of 3 peaks challengers, some are so tired and entrapped in their self ambitions of achieving what is to me a fairly menial pursuit, that they'll ignore, dismiss or ask me to stop talking about the nature as they have no time. I'd rather do the 3 peaks in 28 hours and learn something about starry saxifrage, flow banding, anabatic winds, or sheep.

During my last visit on Sunday, I had an astute group, who allowed me to find and bang on about the fossils which can be seen and found on and around the summit.
These are Brachiopods, similar to clams or cockles. They would have been chilling out in the sandy/silty seabed about 450 000 000 years ago.  Unfortunately for them, at this time there were a couple of local eruptions kicking off. The pyroclastic ash and some magma type substances landed on top of these creatures, buring and preserving them into rock. This semi-tropical seabed, then got churned around with the continental plate techtonics causing Snowdonia to be driven upwards, then being weathered down to exist in it's now raised mountainous domain.

The summit of Snowdon is the meeting point of a few different types of rock. There are areas of superficial deposits of Talus (posh word for scree), formed about 3 million years ago derived from cliffs, ridges and broken steep grounds.

There is also a superficial area/layer of head polymict deposit, grit/gravel/sand, again from 3 million years ago, derived from solification, hillwash and soil creep.

The main rock types are Pyroclastic Bedrock Formation, a basaltic tuff formed between 451-461 million years ago, which leads up to the summit, then on the very top area, I think there is upper Rhyolitic tuff, but I'm struggling to find a source for this. Please contact me if you know for sure.
If you're interested and want to see some of this wonderful geology, get in touch and maybe check out some of my hillwalking courses and guiding, and I can show you these fossils, they're a tough spot otherwise. For the most amazing phone app check out iGeology by the British Geological Survey, its Free! I also went for a educational walk through the Llanberis pass with Paul Gannon as part of my MIA CPD, he has written a fabulous book on the local geology. There are sections of geology in nearly every climbing guide book written to let you know the rock types you're faced with. And many other nature books for the area as well as more national types like the Collins Guide. This kind of thing is top knowledge to have should you be involved in the Mountain Training scheme such as Single Pitch Award, Mountain Leader and Mountaineering Instructor Awards.