Kisdon Hill in Swaledale 2010

1

OPEN UNIVERSITY GEOLOGICAL SOCIETY
YORKSHIRE BRANCH
“ON THE ROCKS”
December 2010

Kisdon Hill in Swaledale 2010.

Contents

1)Branch Committee Officers.

2) Diary of future branch events.

3)A Letter from the Branch Organizer.

4)Future Events

5) Recent Field Trips, Outings and Lectures with YOUGS.

a) Further Exploration of Swaledale.

b) Mineralogy at the Natural History Museum.

(reports to follow in later editions of OTR to make room for David Rowe’s excellent and detailed account of the Late Devensian Glaciation in the Vale of York)

6) GEOLOGY IN THE NEWS:

Galeras, another Mt. St. Helens in the making ?

7) OCCASIONAL ARTICLE:

Changing Views On The Late Devensian Glaciation Of The Vale Of York.

8)The Minutes of the last AGM.

1) Committee Members

Branch Organiser
Treasurer
Newsletter Editor
Librarian
Information Officer
Committee Member
“
“
“
“
“
“
Webmaster
** Ann.Goundry.
*** David.Cousins. / Geoff Hopkins
Ann Goundry**
David Cousins***
Peter Roberts
Dave Williams
Jean Sampson
Jenny Jennings
Pamela Ross
Phil Robinson
Margaret Bemrose
Michael Gagan
Dave Beever
10, Haigside Drive
Rothwell,
Leeds, LS26 OTE
33, Adlard Road,
Doncaster, DN2 5NQ / 01302 882 144
0113 2829 798
01302 366841
01653 618 878
01642 722 452
0114 236 1258
07891 439 686
01757 268 994
01484 460 211 /






Pamela.y.ross@btinternet .com

2) Letter from the Branch Organiser

It is unfortunate that this unexpected deluge of snow and freezing weather upset our plans to visit the National Stone Centre but I am now looking to re-schedule this visit for next March. Let us hope also that the atrocious weather does not continue into January and disrupt our holding the AGM as it did earlier this year. Our intended speaker for the 2010 AGM was Linda McArdell, OUGS committee member, who I am pleased to say has agreed to come along to the 2011 AGM and present a talk and discussion on “Laki – is it the smoking gun”. I am sure that this will be highly interesting and informative and look forward to seeing as many of you as possible at the AGM to give your support. This issue includes the notice of the AGM and also the minutes of the last AGM.

Some provisional dates have been entered for events for the first half of next year but these will be firmed up and confirmed shortly.

May I wish you all a Merry Christmas and a Happy New Year.

Geoff Hopkins

2) Diary of Future Branch Events.

AGM. Saturday:January 22nd. 2011

The AGM of the YOUGS to be held at the Friend’s Meeting House York. Friargate, York 10 am for 10.30 start. The agenda is as follows:-

1)Welcome and register of attendees

2)Apologies

3)Minutes of the last AGM

4)Matters arising

5)Officers Reports

6)Election of Officers

7)Any other business

If anyone has any matters that they wish to raise or air at the AGM please let Geoff Hopkins know prior to the AGM so that these can be included in any other business.

February. Ann Goundry's "Snowflake" weekend in Scarborough. Dates to be confirmed. Contact Ann Goundry.

19th March National Stone Centre, Wirksworth. Contact Geoff Hopkins

23rd April Ingleton Waterfalls Walk. Hopefully this will be lead by Dr John Varker but to be confirmed. Contact Geoff Hopkins

May - The Craven Fault Zone around Settle. Leader and contact Dave Beever

June North Yorkshire. Either Flamborough /Filey or around Great Ayton

Weekend 1st July - Gold panning with Pamela Ross in Scottish Southern Uplands

August 19th - 21st. National Symposium in Stirling

4) GEOLOGY IN THE NEWS:

The Geological Hazards of Galeras

Pasto with a population of 450,000 is nearly 9,000 ft. up in the Andes close to the border with Ecuador, and just a 100 km. north of the Equator. Six km. west of Pasto is the volcano of Galeras. just over 14,000 ft. high and much the same size as Mont. Blanc in the Alps or Mt. Ranier above Seattle.

Galeras is just below the snowline at this latitude. There are no glaciers, little snow and few lakes on Galeras. Lahars have not been a problem to date. Pyroclastic flows, though usually thin, are fairly frequent.

Galeras is a strato – volcano composed of relatively weak unconsolidated rocks, layers of lava ash and rubble. Lavas from Galeras are 58 - 65% silica, andesitic or dacitic and rather viscous giving rise to explosive vulcanian eruptions.

Injuries have been infrequent on Galeras except for the tragic loss of 7 vulcanologists and 4 others in 1993. This party reached the summit when a large explosion threw them to the ground. A survivor described the eruption as like a sonic boom followed by a noise like the splitting of the Earth and a rain of rocks and lava.

This graph shows the number of times that Galeras has erupted each year from 1539 when Pasto was founded until 2010. Notice that there were very few eruptions in the first century of Pasto’s existence but there have been about two periods of heightened activity per century since that time.

In all there have been at least 150 eruptions of Galeras since 1539 and after about 40 years of relative inactivity Galeras gradually awakened again in 1988. This year Galeras has erupted in January, August and November, with a red alert in August.

Today nearly half a million people live on the flanks of the volcano and the recent increase in eruption rate may mean that a mass of magma is moving towards the surface.

A Satellite Photo of Galeras and Pasto

The light area in the center of the picture is the volcano with its horse- shoe caldera, open to the west. The caldera is about the same size as Meteor Crater in Arizona. The lighter patch, bottom centre is Pasto. The picture is about 20 km from left to right.

Usually there are only small quantities of lava erupted but pyroclastic flows are frequent and have reached as far as 10 km from the summit.

Galeras is a strato – volcano, a weak pile of unconsolidated layers of lava ash and debris Three collapses have occurred in the Holocene, producing large debris avalanches which have swept down the flanks of the volcanic complex sometimes travelling 15 km. The last such collapse occurred about 5,000 BC.

This is a Hazard Zone Map produced by (INGEOMINAS.) The Institute of Geology and Mining for Columbia.

The darker area is high risk. Ther are small areas of medium risk and the lighter areathe low risk zone. Half a million people live in the yellow area, the majority in Pasto. With the increasing activity of the volcano this lighter zone is becoming a medium to high risk area.

The first step in dealing with a potential future catastrophe is documenting past volcanic activity and debris flows. Much has been done recently in the way of carbon dating and the careful mapping of at least 200 new sections. Galeras is also being monitored by the World Volcano Organisation. Heat detecting satellites, GPS, microgravity, resistivity and residual magnetism are being checked.

The Volcano Observatory in Pasto keeps a daily log and makes daily observations of seismicity and ground deformation which remain the foundation of volcano monitoring.

In an ideal world Pasto should be rebuilt elsewhere and it may come to that for the siting of Pasto is a medieval mistake. In the meantime a workable mass evacuation plan needs to be developed and a mass education programme is needed to ensure that all citizens are aware of the hazards and know what to do in an emergency

This picture is of the Eruption of 1936.The plume is around 12 km high and a pyroclastic flow can clearly be seen moving northward down the slopes of Galeras. I have tried to show you that Galeras has the potential to be one of the most dangerous volcanoes in the world today but with good planning the consequences of a major eruption may be much reduced but never eliminated. There is a feeling among those responsible for risk assessment that the volcano is working up to a large eruption. Somebody knowledgeable and experienced needs to be in charge at times of heightened activity to avoid the mistakes of Nevado del Ruiz which cost the lives of 23,000 in 1985.

David Cousins

5) Occasional Article.

Changing Views OnThe Late Devensian Glaciation Of The Vale Of York.

Introduction and Background

A widely accepted recent general picture of the Late Devensian glaciation (Dimlington Stadial) of eastern Yorkshire includes the following important elements:

1. An ice sheet with sources in south-eastern Scotland and the Cheviots (with other contributions from Northumberland and Co. Durham) flowed southwards down the east coast of England as far as the north coast of Norfolk between about 23 000 and 15 000 years ago. The ice sheet deposited tills along the east coast – the Blackhall Till of Co. Durham, the Lower Till Series in eastern parts of North Yorkshire, the Skipsea Till of Holderness, at least part of the Marsh Tills of east Lincolnshire, and the Hunstanton Till of north Norfolk (Catt, 2007, P. 201).
2. Some of this ice penetrated river valleys in east Yorkshire as indicated by moraines (at Lealholm in Eskdale, Wykeham in the Vale of Pickering, Brough/Winterton area in the River Humber) which blocked drainage to the sea and caused the formation of glacial lakes upstream. One such was Glacial Lake Pickering; another (of special importance for the present account) was the large Glacial Lake Humber which occupied the southern part of the Vale of York. This lake was created by closure of the Humber Gap between the Yorkshire and Lincolnshire Wolds, damming drainage to the sea from the Vale of York and the Trent and Ancholme valleys (Gaunt, 1980).
3. An ice stream from the eastern Lake District, with contributions from south-west Scotland and the Pennines, flowed eastward over Stainmore and down into Lower Teesdale where it split into two branches:
   (a) one branch continued eastwards north of the Cleveland Hills to meet the North Sea ice in the Teesmouth area and ride onto it to form the upper tier of a composite North Sea ice sheet from which lower and upper tills (Skipsea and Withernsea Tills respectively) were deposited on the Yorkshire coast (Gaunt, 1980; Catt, 2007);
   (b) the other branch turned south into the Vale of Mowbray and advanced into the Vale of York “probably reaching the Isle of Axholme in north-western Lincolnshire (Gaunt, 1976) before quickly wasting back to a more prolonged front, where the crescentic till, sand and gravel ridges of the York and Escrick moraines were formed” (Gaunt, 1980). Direct contributions to the Vale of York Glacier also came from the Pennines down Swaledale, Wensleydale and Nidderdale (Catt, 2007, Pp. 193/194).

Up to the middle 1970s the Escrick Moraine was regarded as the southern limit of glacial ice in the Vale of York as, for example, by Kendall and Wroot (1924) and Penney (1974). Although there had been some earlier tentative suggestions of Devensian ice having advanced beyond the Escrick Moraine, the main protagonist from 1976 for an ice limit south of the River Humber was Geoffrey Gaunt of the then Institute of Geological Sciences, now the British Geological Survey, who took a line of discontinuous sand and gravel deposits exending south-east from near Selby (East Cowick-Thorne-Wroot) as the western margin of the ice lobe (Gaunt, 1976, Fig. 1). The southern limit of the Vale of York Glacier in the Isle of Axholme was evidently accepted officially and in 1977 it was given cartographical expression in the 1:625 000 Geological Survey Ten Mile Map of Great Britain, South Sheet, First Edition (Quaternary); the southern limit was also shown in maps in subsequent Geological Survey publications including two British Regional Geology guides (Kent, 1980, Fig. 27) and (Aitkenhead et al., 2002, Fig. 33), although in the latter case the extension was qualified as a “Possible Transient Ice Surge”. Straw (2002) was critical of the supposed southern limit of the Vale of York glacier, pointing to the general absence of Devensian till south of the Escrick Moraine, the absence of river diversions around the postulated ice lobe, and the absence of marginal gravels on its eastern side comparable with the tenuous Wroot-Thorne Gravels on the western side; for these gravels he offered an alternative explanation as pre-Devensian glaciofluvial deposits. Catt (2007) noted these arguments in his review (P. 194) but while cautiously saying on P. 201 that the Vale of York Glacier “terminated either at the Escrick Moraine or briefly, after a surge, at the East Cowick-Thorne-Wroot line” he opted for the southern limit in his map (Fig. 2).

Recent Developments

In 2008, following a resurvey mainly between 2001 and 2004, the British Geological Survey produced a revised 1:50 000 Bedrock and Superficial (formerly Solid and Drift) geological map of the Selby district (Sheet 71) and a sheet explanation for it (Ford et al., 2008); two of the authors of the latter also contributed to the explanation for Sheet 70, the map of the adjacent Leeds district immediately to the west of the Selby district (Cooper and Gibson, 2003). The two maps cover some of the Vale of York with parts of the York and Escrick moraines and both sheet explanations include sections on the Quaternary; (oddly, the spellings Escrick and Eskrick are used apparently indiscriminately in the Leeds sheet explanation).

In each sheet explanation there is an outline map of the regional glacial geology covering an area of northern England extending from about 10 km north of Scarborough to about 20 km south of Doncaster and from the Pennines to the coast; the two outline maps are at the same scale (albeit with different colour schemes). Both maps show Devensian glacial deposits extending down the Yorkshire and Lincolnshire coasts, and down the Vale of York as far as and including the Escrick Moraine; Glacial Lake Humber, the Vale of Pickering Glacial Lake, and a Vale of York Glacial Lake are also shown identically on the two maps. But there are significant differences in the interpretation of the Devensian glaciation of the southern Vale of York in the two publications; whereas Figure 6 of the Leeds version shows the maximum ice limit of the Devensian glaciation in the Vale of York as in the Isle of Axholme area of north Lincolnshire (as in the Regional Geological Guides cited earlier), Figure 3 of the Selby version shows the limit as at the front of the Escrick moraine – thus reverting to the interpretation that was formerly standard up to the mid-1970s; consistent with this, patches of glacial deposits along the western edge of the Yorkshire Wolds beyond the Escrick moraine shown as Devensian in the Leeds version are shown as pre-Devensian in the Selby version.

These differences are also apparent from a comparison of the following passages of text (omitting parenthetic references) from the Leeds and Selby sheet explanations:

(1) From the Leeds Sheet Explanation (Cooper and Gibson, 2003, Pp. 11-12).

“During the glaciation, the Vale of York ice advanced as far south as Doncaster, and the North Sea ice advanced to Norfolk blocking the drainage through the Humber gap. In front of the ice, fluvioglacial outwash deposits and proglacial lake deposits were formed in the dammed preglacial valley system. Subsequently, as the ice advanced to the Devensian maximum at Doncaster, it overrode these deposits and built up a marginal belt of gravels and till, the Linton-Sutton kame belt. The ice then retreated northwards and the lobate York Moraine and Eskrick Moraine mark temporary still-stands in the vale.

(2) From the Selby Sheet Explanation (Ford et al., 2008, Pp. 10-11).

“The Devensian Stage brought the last glacial events to affect the Vale of York. During this time, ice-flows down the North Sea blocked the Humber estuary and impounded drainage from the Vale of York, creating a vast lake known as Lake Humber. Fine-grained proglacial sediment deposited in this lake is preserved as the Hemingbrough Glaciolacustrine Formation.

“Ice also advanced southwards down the Vale of York, ploughing into the northern part of Lake Humber. Deposits of till represented by the Vale of York Formation were laid down by the ice as it rode over the lake sediments, forming morainic ridges at the front of the ice-flow. The southern limit of the Devensian ice in the Vale of York is marked by the Escrick Moraine.”

Evidently the idea of the Vale of York Glacier having advanced beyond the Escrick Moraine to the Isle of Axholme has been abandoned in the later Geological Survey publication. The second excerpt above also points to two other respects in which opinions about the glaciation of the Vale of York have changed as a result of the resurvey of the Selby district.

1. Glacial Lake Deposits and the Moraines.

Both the Leeds and Selby sheet explanations include similar sized schematic N-S cross-sections across the York and Escrick Moraines and beyond (Cooper and Gibson, 2003, Fig. 7; Ford et al., 2008, Fig. 5). The cross-section in the Leeds explanation shows laminated clay and sand deposits from Glacial Lake Humber as proglacial sediments abutting against the Escrick Moraine; by contrast, the cross-section in the Selby explanation shows the Hemingbrough Glaciolacustrine Formation extending under both the Escrick and York Moraines. According to the text (Ford et al., Pp. 11-14) the laterally persistent Hemingbrough Glaciolacustrine Formation, a sequence of up to 24 m of laminated clay with occasional sand beds resting on bedrock or underlain by Basal Glaciofluvial Deposits, is a tripartite formation comprising the lower Park Farm Clay Member, the middle Lawns House Farm Sand Member, and the upper Thorganby Clay Member; of the Park Farm Clay Member it is written that: