News

A few places are available on this 3 day field trip which will look at the Palaeozoic rocks with particular emphasis on the mineralization.   The party will gather at Melrose Guest House, Douglas, on the evening of 11th July for briefing and disperse on the morning of Friday 15th July.

Bed and breakfast accommodation has been booked at the Melrose Guest House in Douglas and transport on the Island will be by minibus.   Accommodation is available in twin or one triple bedroom.   There are no single rooms.

Cost £170 per person to cover B&B accommodation for 4 nights and minibus transport for the three days in the field, handouts and leader’s expenses.    Lunch and evening meals are not included.

If you would like to go on this trip please contact our event organizer using the online form available here.

Please report by between 9.45 and 10.00 at the originally arranged point i.e. outside the Tourist Information Office (temporarily closed) at the main Glenridding  car park. You will then be re-directed to a nearby location where you can park for the whole time ( a single all day charge of £3 per vehicle is due in the box by the gate of this location).

We will then walk from this location back to Glenridding pier to start the trip. We will return to the cars for a lunch stop and then walk to the other side of the valley via Side Farm for the afternoon session. This will involve a short ascent up to a rough path which will give us fine views over the surrounding area and access to outcrops of the local volcanic rocks.

Facilities [toilets, hot drinks, shop] are available at Glenridding.  Leader John Rodgers 01768 895743  mob. 07816769918 but be aware there is poor network single around this area.

The World’s Largest Caves, by Richard Walters

The speaker started with some spectacular images of the UK’s longest cave system, across the borders of Cumbria, Yorkshire and Lancashire – hence the Three Counties cave.

He explained his interest in locating, and measuring by laser, the largest cave caverns in the world. The overall largest is the Miao Room in China, where it took seven days underground to record its size.

He explained the technology which enables 3D images of the inside walls of the chambers to be produced. These images can then be rotated and linked to surface topography. After much computer manipulation, animations can show the entrance into the caves, views of the enormous stalagmite formations, and an idea of the extent of the cave, which cavers themselves cannot see at the time. Using simple diagrams, the formation of large caverns was explained.

Water meeting from different channels underground becomes aggressive again, and can dissolve more limestone. Stress on the arch structure of the cavern roof was explained as keeping these enormous cavern roofs standing, while unstressed rocks collapses into loose blocks. The fate of all large cavern chambers is to collapse, especially when chambers have an open roof. Yorkshire’s Hull Pot is believed to be a collapsed cavern.

3D images of the underground workings of Nenthead mines were shown, and finally the 3D laser plotted the inside of the meeting room, together with all CGS members. It was a truly memorable illustrated talk, taking us underground without having to make any effort.

A write-up of the event on 10th February 2016 by Sylvia Woodhead.

New 2016 events have been added to our calendar. Check your newsletter, or have a look at the website Events Page here: https://www.cumberland-geol-soc.org.uk/events/

We are hosting meetings throughout the year and even have options for the ever reliable Cumbrian weather so, we expect to see you rain or shine!

Friends and non-members are encouraged. For additional information visit the events page. Should you have any questions, please contact us using the online form.

To find out more about CGS activities and latest updates you can subscribe to the free email alerts on most pages of the website.

Regards,
Cumberland Geological Society

The Lake District’s tuff hailstones – accretionary lapilli AKA birds eye tuff, also known as pheasant‘s eye tuff, by Clive Boulter

Clive Boulter explained using animations and video clips that the bird’s eye tuff of the BVG may not necessarily have been formed in thunderstorms created by volcanic explosions. A classification proposes three types; pellets, coated pellets and accretionary lapilli. An elongated distortion of the pellets in the well-known ‘bird’s eye tuff’ in Kentmere has enabled a calculation of 50-60% shortening of the Earth’s crust in the ‘slate belt, where cleaved’, as plates converged in the period of Ordovician volcanic activity in the Lake District.

A 1820s painting based on Pliny’s account of the Vesuvius eruption of AD 79 was used in an animation to show how lapilli tuff forms in explosive volcanoes with lots of water; a Phreatoplinian type of eruption. Magma is shredded into ash in a strong thrust of gas from the volcanic vent. This rises in a column, eventually spreading and the particles drop, some as ash pellets. Accretionary lapilli may also form when part of the pyroclastic flow moving down the side of an explosive volcano lifts up into a ‘Phoenix cloud’. Ash pellets become coated as they sink into the flow, stick together and are lithified.

BVG vulcanicity began with the eruption of andesite lavas from fissures, which opened due to crustal extension, despite overall plate convergence, to build up as a plateau. Tens of cubic kilometres of water entered the magma chamber to create a Phreatoplinian eruption, with repeated pyroclastic eruptions and caldera collapse. The Scafell caldera was 20 x 20 km in size. Later a lava dome, caldera lake and tuff ring finished the vulcanicity. The volcanoes of BVG of the Lake District are interpreted now as low plateaux, rather than the steep-sided composite volcanoes which featured in earlier reconstructions.

Thanks to Sylvia Woodhead for this write-up of the 20th January event.

The CGS Members’ Evening which was cancelled due to floods, will now be combined with the AGM on Wednesday 2nd March 2016.

The venue for the meeting will be BRAITHWAITE INSTITUTE, CA12 5TD on the A66 at Braithwate near Keswick because the venue originally booked is still being repaired from flood damage.

The previously scheduled talk by Dr. Pottas on the Yorkshire Potash Mine will now take place on 21st September 2016.