To many the land between Bacup and Todmorden is a bare moorland environment, but it is one of human and geological history. The Flower Scar Road is a Bronze Age highway across Todmorden Moor and until the turnpike road was built in the 1780s (now the A681) this was the only road connecting Bacup and Todmorden. Nowadays it is a track only meant for feet, and not four wheels, please do not try and drive on it. From up here there are wide ranging views of the surrounding area. The turbine access tracks mean an easy high level walk to the earth cache site.
On first view, you may wonder why have I been brought here, it appears at first to be an area of industrial waste land. This is the site of the Sandy Road Colliery. The hills around here, were once a hive of industry, though most colliery sites in the area are now almost, or completely invisible, only identifiable from map evidence and mining histories. Even the high moorland mining sites have slowly disappeared under grasses and peat bogs, leaving little evidence apart from unnatural irregularities in the landscape, and trial holes and bell pits across parts of the moorland. A whole industry has all but vanished.
Unlike disused lowland colliery sites, there has been no land re-use or restoration work carried out after the moorland mines were abandoned. One of the last to close, in 1964, was Sandy Road Colliery in the centre of Todmorden Moor. This mine site has not had time to disappear into the landscape. Mounds of colliery wastes disfigure the moorland - too steep and acid for regrowth of vegetation. The foundations of a small mine building remain, and unidentified metalwork at the top of the colliery tramway (now removed, but still marked on many maps). No other evidence of the mine exists above ground, and the entrance to Todmorden Moor mine has been blocked up for safety reasons.
The rocks of Todmorden Moor are Upper Carboniferous in age and are about 310 million years old. At the time northern England was part of a delta covered by rain forest, and cut by meandering river channels. England was located just north of the equator at that time in the tropical wet belt. Sometimes sea levels rose so that water covered the marshes and swamps of the rain forest, bringing in marine shells which then became fossilised in layers of mud. Todmorden Moor was on the eastern limits of the Lancashire coal field.
What is Coal?
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as a metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon, along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. It is a fossil fuel and forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite.
Lignite, often referred to as brown coal, is a soft brown combustible sedimentary rock. It is considered the lowest rank of coal due to its relatively low heat content. It has a carbon content around 60–70%.
Anthracite is a hard, compact variety of coal that has a sunmetallic luster. It has the highest carbon content, the fewest impurities, and the highest calorific content of all types of coal except for graphite. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%
Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite coal lbut of poorer quality than anthracite. Formation is usually the result of high pressure being exerted on lignite. Its colouration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. These distinctive sequences, which are classified according to either "dull, bright-banded" or "bright, dull-banded", is how bituminous coals are stratigraphically identified. Bituminous coal is an organic sedimentary rock formed by diagentic and sub metamorphic compression of peat bog material. Its primary constituents are macerals : vitrinite, and liptinite.
The Lancashire Coalfield was one of the most important British coalfields, The geology of the coalfield consists of the coal seams of the Upper, Middle and Lower Coal Measures,layers of sandstones, shales and coal of varying thickness. The coal in Lancashire is bituminous with 30–40% volatile matter varying in hardness from seam to seam.
The location is renowed for Coal Balls, which are not associated with other mines in West Yorkshire and are rare across the whole of the UK
What are Coal Balls?
Coal balls are extremely hard concretions found within certain, but by no means all, coal seams that were overlaid by marine strata - and are described by as "exceptionally preserved calcareous permineralised peat". They vary in size from 2 inches to 2 feet in diameter, often circular or elliptical but sometimes irregular in shape. Many are found to contain excellent evidence of plant structures completely petrified by secondary carbonate materials and clearly show the delicate tissues of bog flora of the carboniferous period. Coal balls are associated in the UK with Central East Lancashire, particularly the Burnley area where they were often in some concentration. The seams concerned are the Upper Foot and Lower Mountain Mines of East Lancs. The Todmorden Moor collieries were on the eastern edge of this coal field. Their presence within the local coal seams could, and did, result in seams becoming unworkable because of the damage to mining machinery. As late as 1967 the Colliery Guardian ran articles on efforts to overcome the very expensive damage to picks, drums and cutting jibs in the N.E. Lancs. coal workings.
You may not find a coal ball, but the spoil heap is a good place for finding fossils. You will have to look hard though.A spoil tip (also called a spoil bank, boney pile, gob pile, bing, batch, boney dump or pit heap) is a pile built of accumulated spoil - the overburden or other waste rock removed during coal and ore mining. These waste materials are typically composed of shale, as well as smaller quantities of carboniferous sandstone and various other residues. Spoil tips are not formed of slag, but in some areas they are referred to as slag heaps. The term "spoil" is also used to refer to material removed when digging a foundation, tunnel, or other large excavation. Spoil tips sometimes grew to millions of tons, and, having been abandoned, remain as huge piles today. They trap solar heat, making it difficult (although not impossible) for vegetation to take root; this encourages erosion and creates dangerous, unstable slopes.
What is a fossil?
Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (Strata) is known as the fossil record.
The process of fossilization varies according to tissue type and external conditions.
(1) Permineralization
This is a process of fossilization that occurs when an organism is buried. The empty spaces within an organism (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater. Minerals precipitate from the groundwater, occupying the empty spaces. This process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils. For permineralization to occur, the organism must become covered by sediment soon after death or soon after the initial decay process. The degree to which the remains are decayed when covered determines the later details of the fossil. Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues.
(2) Casts and Molds
In some cases the original remains of the organism completely dissolve or are otherwise destroyed. The remaining organism-shaped hole in the rock is called an external mold. If this hole is later filled with other minerals, it is a cast. An endocast or internal mold is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull.
(3) Authigenic mineralisation
This is a special form of cast and mold formation. If the chemistry is right, the organism (or fragment of organism) can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. If this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved.
(4) Replacement and recrystallization
Replacement occurs when the shell, bone or other tissue is replaced with another mineral. In some cases mineral replacement of the original shell occurs so gradually and at such fine scales that microstructural features are preserved despite the total loss of original material. A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form.
(5) Adpression (compression-impression)
Compression fossils such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state. This chemical change is an expression of diagenesis. Often what remains is known as a phytoleim, in which case the fossil is known as a compression. Often, however, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil.
Sedimentary Rocks
Among the three major types of rock, fossils are most commonly found in sedimentary rock, these are layered or “stratified”. This is because over the years conditions changed leaving different layers in the sediment. Sometimes the sediment would be mud, whilst at other times it would be sand. There were even times when pebbles were washed down to form a layer of pebbles mixed with sand. The different layers eventually turned into rocks with different properties. Coarse grained sedimentary rocks, perhaps containing pebbles, are known as gritstones, but in the past have been called ‘grits’ leading to the name Millstone Grit; medium grains equal ‘sandstone’; finer grains give rise to ‘siltstones’. The finest grained sedimentary rocks were once mud and are often dark coloured. Formerly known as ‘shale’ they are now referred to as ‘clayrock’. Typically the rock sequence is alternating layers of strong brown sandstones, softer dark shales (clayrock) and occasional gritstones.
This being an earthcache, there are questions to answer in order to log your find, please send the questions to me, and do not include in your log. Please feel free to log your find, and submit the answers at the same time. There is also a noticeboard at the location which may be of some help.
(1) How is coal formed and how many types are there? How are they different from each other?
(2) During which geologic period was the coal laid down?
(3) What type of coal was mined here?
(4) Go to the spoil heap , what type of rock predominantly makes up the spoil heap? (a) Describe what colour is it, (b) how does it feel, (c) How thick is the rock ?, (d) Is there any vegetation on it, if not why not?, (e) Please compare the temperature of the spoil heap to the surrounding ground, is there any difference, if so which side if warmer?
(5) Now there are fossils in the spoil heap, I find the eastern, and north eastern facing slope is the best place. If you find what you think is a fossil, please describe what it looks like and include a photograph with your log if you are able to take a picture. If you cannot find a fossil do not worry, I will not delete your log for this.
(6) What is a fossil?
(7) So coal was mined here, can you find some, how is it different from the rest of the material in the spoil heap? How much in an approxiamete percentage is there compared to other material in the spoil heap, why do you feel that there is such a percentage and not more or less?
(8) (a) How high is the spoil heap in metres please? (b) At what angle in degrees does the north eastern flank of the spoil heap lie at?