Mere (lake)
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Mere in British English refers to a lake that is broad in relation to its depth, e.g. Martin Mere. A significant effect of its shallow depth is that for all or most of the time, it has no thermocline.
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[edit] Derivation of the word
The word has the same derivation as the Latin mare or Dutch meer and once included the sea or an arm of the sea, in its range of meaning but this marine usage is now obsolete (OED). It is a poetical or dialect word meaning a sheet of standing water, a lake or a pond (OED). The OED's fourth definition betrays a confusion between mere and wetland such as fen in the minds of users of the word which is reflected in the lexicographer's recording of it. In a quotation from the year 598, mere is contrasted against moss (bog) and field against fen. The OED quotation from 1609 does not say what a mere is, except that it looks black. In 1629 mere and marsh were becoming confused. But in 1876 mere was 'heard, at times, applied to ground permanently under water': in other words, a very shallow lake. The online edition of the OED's quoted examples relate to:
- the sea: Old English to 1530: 7 quotations
Windermere (viewed from the north: about grid reference NY4003).
- standing water: Old English to 1998: 22 quotations
- arm of the sea: 1573 to 1676: 4 quotations
- marsh or fen: 1609 to 1995: 7 quotations
From this it is clear that the balance of the way the word has been interpreted has changed with time but that the 'lake' view of it is the predominant and persistent one. There is the potential for further confusion because the Anglo-Saxon ‘mŏr’, from which the modern 'moor' derives, also refers to low-lying wetlands (such as Sedgemoor, SW England, and possibly the Cheshire meres). [1]
A good indication of what people of the past thought the word meant can be found in place-names. Though care must be taken to avoid confusion with words derived from the same root as the Latin murus (wall) which generally include the concept of 'boundary'.
The name Windermere makes it clear that the narrow meaning adopted by this article has not invariably been taken. Windermere is a lake as much as sixty metres deep in a glacially over-deepened valley. In summer there is a distinct thermocline (M&W). A lot of the lakes in the Lake District are in fact meres. On Wimbledon Common in London, there are two meres, Rushmere and Kingsmere which almost certainly result from gravel extraction by hand as deeply as the ground water permitted. Kingsmere is beside the London to Portsmouth road. They are quite uniformly shallow. In the same place, Queensmere is dammed in a small valley so that it is a little deeper and narrower. The pre-drainage Martin Mere, in its shallow depression in the sheets of glacial deposits and the ‘flashes’ of Cheshire, caused by subsidence when underground rock salt deposits have been dissolved away are meres but the archetypal mere is that of fenland which possibly explains the confusion between it and fen. The mere in which Grendel and his mother lived seems clearly to have been of this sort. The Beowulf story, in which we read of them, was probably written in the seventh or eighth century (C-H p.29 though this date is far from secure). OED (Supplement) quotes use of the word mere in translations of the Beowulf story from 1849 onwards.
[edit] Characteristics
Where land similar to that of Martin Mere, gently undulating glacial till, becomes flooded and develops fen and bog, the remnants of the original mere remain until the whole is filled with peat. This can be delayed where the mere is fed by lime-rich water from chalk or limestone upland and a significant proportion of the outflow from the mere takes the form of evaporation. In these circumstances, the lime (typically calcium carbonate) is deposited on the peaty bed and inhibits plant growth therefore peat formation. A typical feature of these meres is that they are alongside a river rather than having the river flowing through them. In this way, the mere is replenished by seepage from the bed of the lime-rich river, through the river's natural levée, or by winter floods. The water of the mere is then static through the summer, when the concentration of the calcium carbonate rises until it is precipitated on the bed of the mere.
Even quite shallow lake water can develop a thermocline in the short term but where there is a moderately windy climate, the circulation caused by wind drift is sufficient to break this up. (The surface is blown down-wind in a seiche and a return current passes either near the bottom or just above the thermocline if that is present at a sufficient depth.) This means that the bed of the shallow mere is aerated and bottom-feeding fish and wildfowl can survive, providing a livelihood for people around. Expressed more technically, the mere consists entirely of the epilimnion. This is quite unlike Windermere where in summer, there is a sharp thermocline at a depth of 9 to 15 metres, well above the maximum depth of 60 metres or so. (M&W p36)
At first sight, the defining feature of a mere is its breadth in relation to its shallow depth. This means that it has a large surface in proportion to the volume of water it contains. However, there is a limiting depth beyond which a lake does not behave as a mere since the sun does not warm the deeper water and the wind does not mix it. Here, a thermocline develops but where the limiting dimensions lie is influenced by the sunniness and windiness of the site and the murkiness of the water. This last usually depends on how eutrophic (rich in plant nutrients) the water is. Nonetheless, in general, with the enlargement of the extent of a mere, the depth has to become proportionately less if it is to behave as a mere.
[edit] The meres of the English fenland
The Fens of eastern England, as well as fen, bog and other habitats included a number of meres. As at Martin Mere in Lancashire, when the fens were being drained to convert the land to pasture and arable agriculture, the meres went too but some are easily traced owing to the characteristic soil. For the reasons given above, it is rich in both calcium carbonate and humus. On the ground, its paleness stands out against the surrounding black, humic soils and on the soil map, the former meres show as patches of the Willingham soil association, code number 372 (Soil Map).
Apart from those drained in the medieval period, they are shown in Saxton's map of the counties (as they were in his time) of Cambridgeshire and Huntingdonshire. The following is a list of known meres of the eastern English Fenland with their grid references.
Saxton's meres are named as:
- Trundle Mere TL2091
- Whittlesey Mere TL2291
- Stretham Mere TL5272
- Soham Mere. TL5773
- Ug Mere TL2487
- Ramsey Mere TL3189
In Jonas Moor's 'map of the Great Levell of the Fenns' of 1720, though Trundle Mere is not named, the above are all but one, included with the addition of:
- Benwick Mere TL3489
In the interval, Stretham Mere had gone and the main features of the modern drainage pattern had appeared.
Ugg, Ramsey and Benwick meres do not show in the soil map. Others which do but which appear to have been drained before Saxton's mapping in 1576, are at:
- TL630875
- TL6884
- TL5375
- TL5898
The last appears to be the "mare 'Wide' vocatum" of Robert of Swaffham's version of the Hereward story (Chapter XXVI). If it is, it will have been in existence in the 1070s, when the events of the story took place.
[edit] Meres in the Netherlands
Meres similar to those of the English Fens but more numerous and extensive, used to exist in the Netherlands, particularly in Holland. See Haarlemmermeer, for example. However, the Dutch word meer is used more generally than the English 'mere'. It means 'lake'. When the Zuider Zee was enclosed and its salt water became fresh, it changed its status from a sea (zee) to being known as the IJsselmeer, the lake into which the River IJssel flows.
[edit] References
- ^ Oliver Rackham/The History of the Countryside/Dent 1986/ISBN-13 978-1-8421-2440-6
- Oxford English Dictionary (OED)
- Ordnance Survey 1:50 000 Sheets 142 & 143
- Macan, T.T. and Worthington, E.B. Life in Lakes and Rivers Fontana (1972) (M&W)
- Crossley-Holland, K. The Poetry of Legend: Classics of the Medieval World Beowulf (1987) ISBN 0-85115-456-5 (C-H)
- Soils of England and Wales, Sheet 4 Eastern England Soil Survey of England and Wales (1983) (Soil Map)
- Saxton, C. Christopher Saxton's 16th Century Maps. The counties of England & Wales. With Introduction by William Ravenhill (Cambridgeshire map dated 1576 book 1992) ISBN 1 85310 354 3
- Moor, J. A Map of the Great Levell of the Fenns Extending into ye Countyes of Norfolk, Suffolke, Northampton, Lincoln, Cambridge, Huntingdon and the Isle of Ely facsimile edition by Cambridgeshire Library Service (c1980s)
- Swaffham, R. Gesta Herwardi (ca. 1260) (transcribed by S. H. Miller and translated by W. D. Sweeting (1895-7))
