Bog Oaks and Bog Bodies
Dr. Jonathan Lageard,
Senior lecturer in Environmental Studies,
Manchester Metropolitan University
Widnes SciBar - 11th May 2016
[You can read more about Jonathan's professional work here.]
Types of Bog Bogs form when plants grow and die in locations where there is permanent wetness for many, many years. In such settings, when a plant or tree dies, it doesn’t fully rot owing to the prevailing acidic and anaerobic conditions. Fresh growth then develops on top of what is lying in the bog. Common bog plants include sphagnum moss and cotton grass and various types of trees can grow. Over many years, a significant depth of dead vegetable matter builds up - this is peat. Peat bogs cover nearly 2-3% of the Earth’s surface and are an important carbon sink, containing a significant amount of ‘locked-away’ carbon.
Blanket Bogs (see LHS) occur in fairly flat upland areas, e.g. Pennines, west coast of Scotland; Holme Moss is one of our nearest examples. They are characterized by spiky rushes: the main source of water is rainwater rather than groundwater.
Lowland Bogs (see LHS) - occur where the drainage of water is impeded, such as in a depression. Such sites often date back to the end of the last Ice Age. In Delamere Forest, depressions were left by large blocks of ice during the retreat of the last ice age - some are filled with lakes & some with bogs.
Chat Moss to the west of Manchester, although now much reduced by human activity, used to cover some 25 square kilometres and was 7 to 9 metres deep. It proved a challenge to Stephenson (see LHS) when he was constructing the Liverpool - Manchester railway; his solution was to lay the tracks and ballast on a bed of heather, tree branches and stones, a solution that remains effective today. Other nearby examples are large areas near Southport, e.g. Martin Mere and Balls Farm (on Marsh Rd!).
Drainage & Exploitation Peat has long been used as:-
- a source of fuel (e.g. Scotland & Ireland). Traditionally it was cut by physical labour and stacked up in piles to dry out,
- a soil conditioner; it improves the soil structure, mineral retention, water retention and acidity; usually the bog is drained to make it easier to extract the peat.
However, when used in these ways the trapped carbon is released as carbon dioxide.
From the mid-20th century the exaction of peat was greatly increased by the use of machinery - such commercial activity removes peat at an unsustainable rate, with vast areas of bog having been lost as a result. In some areas (e.g. Duddon Valley in the Lake District) the bog has been drained to make the land suitable for agriculture. Because sphagnum moss has antiseptic properties, it was used for wound dressing in World War I. For some years, gas was extracted from peat in Manchester. Carrington Moss near Manchester was used for the dumping of ‘night soil’ from cesspools & privies before there was mains drainage.
Organic Record Examination of a core taken through the depth of a bed of peat can show what plants that were growing in that location at different stages over many years. A similar record can be obtained for insects such as beetles. Pollutants at different times can also be identified, e.g. the significant use of lead by the Romans.
|Lindow Man on display|
Bog Bodies - Lindow Woman and Man At a commercial peat extraction business on Lindow Moss (near Wilmslow), a small train with moveable track has long been used to transfer peat from where it was dug up to a central processing plant to be sieved, with anything large such as a tree branch being removed, & then prepared for sale. In 1983 a large oval shaped piece was picked out - the workers joked about it being a dinosaur’s egg but it proved to be the head of a woman! This find became known as Lindow Woman. The find received wide media coverage & a local man confessed that he had murdered his wife & buried her body in the peat. Radiocarbon dating subsequently established the remains were nearly 2,000 years old. The husband was convicted on the basis of his confession, the only evidence against him - his wife’s body has never been found!
Soon after (1984) what was first thought to be a branch proved to be a lower leg and foot. When the location of the digging was checked, most of the body was found - eventually called Lindow Man. Because of the possibility that this was a body recently deposited in the peat, the Police were involved & both forensic scientists & archaeologists were called in. Although accurate aging of the body was not possible due to disturbance of the site of the find, it is recognized that the person died in about 200AD. Lindow Man was one of most important archaeological discoveries of the 1980s and it attracted wide public interest, not least because of what could be gleaned about his life, last meal and violent death. Lindow Man is now in the possession of the British Museum.
Further information about Lindow Man is available here.
Tree Rings - an Archive of Information Jonathan explained that when the annual rings in the trunk of a tree are examined, changes in their width and colour due to the season of the year & in weather conditions at the time can be identified. A collection of rings over several years yields a pattern akin to modern barcode that is shared by all trees of the same type growing at the same time. By studying trees of various but overlapping years, a characteristic barcoding can be built up over a thousand years or more. This record can then be used to identify the previously unknown age of any one tree to a high degree of accuracy; this form of dating can often be far more precise than carbon dating.
If a tree section includes the bark the year that the tree died or was cut down can be determined from rings immediately within the bark.
When a section through the trunk of a tree isn’t available for any reason (e.g. a growing tree, a tree that has been used as a building material), a bore can be taken through the trunk to study the tree rings.
|Cross Section of a 3 000 year old Bog Oak|
Bog Oaks When trees that have grown in a bog die, they remain intact whilst in the bog and provide an insight into prevailing conditions up to 5,000 years ago. Whilst they a nuisance to the mechanical peat cutters, they are what Jonathan studies, oaks in particular. Jonathan has studied the remains of oak trees found in bogs in the Mersey catchment area, and has included oak in historic buildings. He brought with him several sections on bog oak dating back up to 5,000 years ago.
Martin Mere, near Burscough (see the previous post from Alan Daglish, and below). This is a Wildlife & Wetlands Trust site &, although much of the surrounding land has been changed by human intervention, it remains a wetland where there has been a bog for hundreds of years. Several bog oaks have been uncovered and are on display at several locations around the site.
Alan Daglish, a regular at Widnes SciBar, is a volunteer in the Education Dept at Martin Mere that presents living history experiences to school children - they can visit a wetland roundhouse village and find out about historical eras such as the Celts, Romans, Vikings. There are also ‘hands on’ experiences such as pond dipping and den building. The village is open to the public Tuesdays and Wednesdays in the summer school holidays.
Accessing Manchester’s Mosslands This is a movement seeking to start the revival of the moss lands at Lindow and surrounding areas, now severely depleted due to the commercial peat removal. One approach is to return the wetness to encourage moss land growth.
Much Appreciation to Jonathan
Jonathan’s talk introduced us to new topic at the SciBar and engaged everyone - at the interval, all present were crowded around the table where the bog oak samples, up to 5,000 years old, were displayed.
22nd May 2016