Friday 29 July 2016

The Shire as a Loess Region: further considerations

"In a hole in the ground there lived a hobbit" -one of the most famous opening sentences. It opened the door (a round door) to the world of the hobbits and the whole history of Middle Earth.  There are three nouns in this sentence; the hobbits have become famous and have accrued a vast literature, but the 'hole' and the 'ground' have been rather neglected- however there is more to be said about 'the hole in the ground', and much discussion to be had  What parameters determine the nature of the hole? what controls the size and nature of the hole?  What sort of ground is the hole excavated in?  How does the nature of the ground affect the nature of the hole?  What grounds are good for holes and where are they located? 

We edge towards the world of soil mechanics for a discussion of the nature of the hole, and we will need to invoke the 'Heneberg Compromise' when discussing the construction of holes. We need to invoke some geomorphological knowledge when it comes to examining the nature of the ground, and we will need a careful interpretation of the few facts and descriptions that Tolkien has given us. Tolkien was a man of words, so the words he has left us need to be examined properly and conscientiously. Take the Brandywine River for example- a case which bears instantly on our discussion. This is properly called the Baranduin and Tolkien noted that it was a yellow river (a golden river), it was a turbid river, it carried a high load of suspended sediment even in the latter days. In glacial times it would have carried a large amount of sediment. The Brandywine defines the Shire.



Tom Shippey provides another sentence: " Creatures that live in holes in the ground ought to be animals- rabbits, moles, snakes, gophers, badgers- and 'hole' conveys a poor impression as a place to live.'  In fact the classic hole living creatures are birds, and in particular members of the family Meropidae- the bee-eaters. In a hole in the ground there lived a bee-eater. These are successful birds who live in many parts the world. The European Bee-eater (Merops apiaster) likes to live in a hole in a loess deposit (as do hobbits).  The bee-eaters have the status of environmental engineers and provide living space for a whole host of creatures.
The geotechnical factors which affect a bee-eater dwelling also affect a hobbit house. The Heneberg Compromise (named for Petr Heneberg of the University of Vienna) points to the need to balance, in the ground being considered, the ease of excavateability and the stability of the opening, the strength of the ground. Easy excavation in weak ground can lead to a collapsible tunnel. Choice of an over-strong ground means great difficulties in excavation. This is why Merops apiaster lives in loess deposits; loess provides a strong rigid ground which can be easily excavated. This is why thousands of Chinese people live in loess houses. Tom Shippey wrote from Leeds, one of the few places that does not experience bee-eaters. Glorious birds living in fantastic colonies- whole cities of holes, conveying a wonderful impression of a place to live.




The similarity of hobbit and bee-eater dwellings offers the strong suggestion that the Shire is loess country; that the geo-conditions were right for the formation of a substantial loess deposit which the hobbits could subsequently exploit. The deterministic approach to the processes of loess deposit formation can be applied to the Shire situation; all the requirements are in place. The loess material can be produced in the cold north, perhaps by continental glaciers, but also by mountain glaciers. This material is carried to the south by the Brandywine river (causing the turbidity) and is deposited on floodplains, and then blown inland. The Shire deposits should be thickest by the river but data on thickness may not be available. Great deposits do exist alongside rivers, the Danube bluffs are an excellent example.
The mountains and the river are well placed, and the descriptions of the Shire fit well with an inhabited temperate loess landscape. The Shire entry in the Tolkien Gateway speaks of a place which is "small but beautiful and fruitful".  Soils developed on loess are the most productive, the classic productive soil is a loess soil, loess regions are fruitful regions. Loess is good for agriculture and it also good for making bricks. Loess is a surficial deposit; access is easy so it is no surprise that early brick buildings in England were built in regions where loess (called brickearth) was found.

Loess bricks have a part to play in the history of the Shire. While Frodo and friends are away dealing with the problem of the Ring the Shire experiences bad times- there is much wanton destruction and quite a lot of unwanted construction. Brick houses are built and much constructional vandalism occurs. And this occurs in a fairly short time; the great adventure takes a few years so it is rapid vandalism, and the really bad times, after the arrival of Saruman, are short. Is there time to produce enough bricks to do the reported damage. It seems unlikely that the hobbit brickyards carried large stocks so bricks had to be made quickly. This points to easily accessible loess ground being turned into bricks- it is hard to see any other earth material being available for this rapid production.

Some literature
Smalley,I., Bijl,S. 1993.  Hobbit holes as loess dwellings and the Shire as a loess region. Amon Hen 122, online at Scribd.com

Smalley,I., OHaraDhand, K., McLaren, S., Nugent, H.  2012.  Loess and bee-eaters I: Ground properties affecting the nesting of European bee-eaters (Merops apiaster L1758) in loess deposits.  Quaternary International 296, 220-226.



Afterthought: the Great East Road.  The Great East Road - ran East-West through Eriador, crossing the Greenway at Bree- from the Grey Havens, through the Shire, through Bree to near Rivendell and over the Misty Mountains, even through Mirkwood. This was a very old road, and it is logical that as it passed through the Shire it would gradually be transformed into a sunken road. This is a characteristic of roads in loess regions, long-term usage causes the road surface to sink, for the road to run in a pronounced valley. People passing though the Shire on the Great East Road would be travelling in a fairly deep valley, largely unaware of the land on either side. Travellers on a major route, particularly a sunken route are often unaware of their surroundings (eg travellers on the M1 road rushing through Leicestershire). There are hints in the writings that the hobbits were undetected, that travellers on the Great East Road were not aware that the Shire was an inhabited region. Travellers on the Great East Road were isolated in their loess valley.

Tuesday 5 July 2016

Loess in Britain XV: Essex


Warren, S.H.  1942.  The drifts of south-western Essex.  Essex Naturalist 27 (part 5, Ap-Sept 1942) 155-163;  27 (part 6, Oct 1942- Nov 1943)  171-179.

"Hallsford-  I call the exposures here my key sections to unlock certain of the secrets of the local geology" [Zeuner's Hallsford loess must be here].

"The other pit is that of the Hallsford Brick & Tile works (E.of High Ongar Road)...  about 3/4 mile SE of Chipping Ongar.  Deposits in fig.1 are:  1. Rainwash, of the Iron Age, up to about 4 ft.  2. Loess, probably of Aurignacian age, up to 8 ft.  3.  a buried land surface..  4. Chalky Jurassic Boulder clay..  5. glacial sands.  6. pebble gravel..  7.  London clay."

"The Hallsford loess- although this is only a small local deposit-  it is one of exceptional interest which Dr. Zeuner has analyses;  he finds it to be a true wind-borne loess (a steppe deposit) of continental type, which was formerly thought to be absent from this country."

Gruhn, R., Bryan, A.L., Moss, A.J.  1974.  A contribution to Pleistocene chronology in south-east Essex, England.  Quaternary Research 4, 53-75


Eden, D.N.  1980.  The loess of North-East Essex, England.  Boreas 9, 165-177.

A thin mantle of cover-loam over much of north-east Essex has been recognised as consisting of loess.  The cover-loam represents the intermixing, to a varying degree, of a layer of loessial silt with a thin layer of underlying sand which is also of likely aeolian origin. The heavy mineral content of the coarse silt fraction of north-east Essex loess is generally similar to that of the last glaciation age loesses elsewhere in eastern England, Belgium and the Netherlands.  This suggests the north-east Essex loess is part of a single loess sheet deposited over Eastern England and parts of western Europe. Nevertheless


...  detailed examination of the heavy minerals content from all of these areas reveals slight areal variations especially in the proportion of hornblende. These differences show the coarse silt from NE Essex loess to have closest affinities with that from Norfolk. A distant source for the loess within the present North Sea basin is proposed on textural evidence. Loess accumulation in NE Essex probably commenced in the few thousand years leading up to the maximum extent of Devensian ice (about 18,000 BP) and may have continued to about 14,000 BP.

 

Monday 4 July 2016

Loess in Britain XIV: HS2

HS2 is a new railway to connect London and Birmingham; to facilitate the flow of commuters in and out of London from the nearby north. This is a major engineering project which will have interesting foundation implications. Its interesting from the LiB point of view because it will be built in the 'Loess Affected Zone' of SE England. Some preliminary studies (Assadi-Langroudi 2016) have indicated that the Hertfortshire loam sequence which HS2 will cross is very similar to the loessic situation at Ospringe. The LAZ reaches just about to Birmingham and thus loess foundation problems might be encountered. The loess problem will not be as acute as it was with the estuary airport but it will require consideration .  
                                                                                                                                              

Loess in Britain XIII Dates & Dating

Wintle A.G.  1981.  Thermoluminescence dating of late Devensian loesses in southern England. Nature 289, 479-480 (05 Feb 1981)  doi:10. 1038/289479a0.

This Ann Wintle piece in Nature is a pioneering application of luminescence dating of loess; maybe the first TL study of loess in UK?

Gibbard, P.L., Wintle, A.G.,  Catt,J.A.  1987.  Age and origin of clayey silt 'brickearth' in west London.  Journal of Quaternary Science  2,  3-9

Clarke, M.L., Milodowski, A.E.,  Bouch, J.E.,  Leng, M.J.,  Northmore, K.J.  2007.  New OSL dating of UK loess; indications of two phases of Late Glacial dust accretion in SE England and climate implications.  Journal of Quaternary Science  22,  361-371.



Ann Wintle:
"Scattered across southern England are many isolated deposits of loess-like material. A few, such as that at Pegwell Bay in Kent, are highly calcareous and unweathered but most have been reworked by fluvial or colluvial processes. There is good stratigraphical evidence for a few pre-Devensian loesses, also in Kent , but dating of more recent loess has so far been based on indirect evidence. Much work has been done on the Pegwell Bay loess as it is the most extensive, truly aeolian loessic deposit in Britain. Kerney compared the late Devensian deposits in the Isle of Thanet and at Pegwell Bay with similar deposits in Holland and Belgium where radiocarbon dates have been obtained for interstadial deposits. Correlations of the East Kent deposits with these in Northern Europe indicates that the loesses in Kent were formed between 30,000 and 14,000 yr.ago. I report here dates for six of the more recent deposits in southern Britain from the Scilly Isles to Kent.  The dates have been obtained on the loess itself, using a recently developed thermoluminescence technique, and confirm the ages as being late Devensian."  (AGW 1981)