Reasons for Studying a Graveyard:
I have chosen to study a graveyard because:
- There are all three rock types: igneous, sedimentary and metamorphic.
- It is relatively easy to see the stones, whereas if I were to study a cliff, for instance, it would be hard to study the middle of the cliff.
- Also the stones are dated making it very easy to grade the stones by age and compare stones of similar ages.
- Furthermore there are different stones in different circumstances (some in shelter), meaning I can have a wide range of data because they are not all the same.
- Finally, it is very easy and convenient to study the graveyard because it is close by and I can therefore return to it if I need to.
Rock Identification:
In order to help me identify the different rocks in the graveyard I created a table of the rock properties (see below). I have also included a brief summary of the three different types of rock:
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Igneous rocks contain crystals both large and small. It is formed when magma cools underground and crystallizes or when it erupts unto the surface of the ground, cools and crystallizes. Magma that erupts onto the surface is called lava. When magma cools slowly underground the crystals are large enough to see. When it cools quickly on the surface, the crystals are very small and you would need a magnifier or a microscope to see them.
- Sedimentary Rock forms from particles, called sediment, that are worn off other rocks. The particles are sand, silt, and clay. Sand has the largest particles while clay has the smallest. If there are a lot of pebbles mixed with the sand, it is called gravel. The sediment gets turned into rock by being buried and compacted by pressure from the weight above it. Another way it becomes rock is from being cemented together by material that has been dissolved in water. Often, both cementing and compaction take place together.
- Metamorphic Rock is formed by great heat, or pressure, or both. The pressure can come from being buried very deep in the earth's crust, or from the huge plates of the earth's crust pushing against each other. The deeper below the surface of the earth, the higher the temperature, so deep burial also means high temperatures. Another way that high temperatures occur is when magma rises through the earth's upper crust. It is very hot and bakes the rock through which it moves. Hot liquids or gases from the magma also can cause chemical changes in the rock around the magma.
Factors Affecting Weathering:
There are many factors that affect the weathering of the gravestone and here I have tried to mention all the major factors with a short explanation of each one:
- Freeze thaw/frost: as water seeps into joints in the rock over night it freezes and expands (by up to 10%) making the rock crack and shatter.
- Biotic weathering: grass roots and roots of other larger plants sometimes grow into the rock causing it to crack over time and break down.
- Furthermore, there is more biotic weathering caused by animals burrowing under the gravestones, causing the rock to breakdown or merely weaken it so that it is more prone to other kinds of weathering.
- There is also another kind of biotic weathering from the lichen that stick to the gravestones, because they secrete an acid onto the stone in order to extract its minerals and this weakens the stone. Please note however, that it is also argued that these lichen actually protect the stone because they prevent the rain, wind etc from touching the surface of the stone. Please see my pilot study for more detail about this and my own opinion.
- Exfoliation is also another visible form of weathering which is caused by the heating and cooling of the rock and causes the skin of the rock to crack and fall off.
- Chemical weathering is also visible in the rock because the rock is dissolved by the mild acid sometimes contained in rain water and the features (e.g. lettering on some stones) fade over time.
- Another less direct factor affecting weathering is the way it faces, for if the stone faces West it is generally more likely to be more open to weathering on the West side because that is where the weather comes from in England.
- There is also the question of shelter, because in the graveyard some stones are protected from weathering by ivy, trees, or even the church itself. This shelter can both help and hinder weathering.
Rock Identification Table:
Does the rock contain many different size and color minerals?
Yes – Igneous Rock No – Sedimentary/Metamorphic Rock
Does the rock contain big or small crystals? Does the rock contain bits of shell or sediment?
Big – Granite Small – Basalt Yes – Sedimentary Rock No -Metamorphic
Does the rock contain straight lines and is it black?
Does the rock crumble easily and is it orange?
Yes – Sandstone No – Limestone Yes – Slate No – Marble
Please Note: I have only included a small amount of the rocks that exist because the above stones are the only ones I think I will need to identify.
Factors Affecting Weathering:
There are many factors that affect the weathering of the gravestone and here I have tried to mention all the major factors with a short explanation of each one:
- Freeze thaw/frost: as water seeps into joints in the rock over night it freezes and expands (by up to 10%) making the rock crack and shatter.
- Biotic weathering: grass roots and roots of other larger plants sometimes grow into the rock causing it to crack over time and break down.
- Furthermore, there is more biotic weathering caused by animals burrowing under the gravestones, causing the rock to breakdown or merely weaken it so that it is more prone to other kinds of weathering.
- There is also another kind of biotic weathering from the lichen that stick to the gravestones, because they secrete an acid onto the stone in order to extract its minerals and this weakens the stone. Please note however, that it is also argued that these lichen actually protect the stone because they prevent the rain, wind etc from touching the surface of the stone. Please see my pilot study for more detail about this and my own opinion.
- Exfoliation is also another visible form of weathering which is caused by the heating and cooling of the rock and causes the skin of the rock to crack and fall off.
- Chemical weathering is also visible in the rock because the rock is dissolved by the mild acid sometimes contained in rain water and the features (e.g. lettering on some stones) fade over time.
- Another less direct factor affecting weathering is the way it faces, for if the stone faces West it is generally more likely to be more open to weathering on the West side because that is where the weather comes from in England.
- There is also the question of shelter, because in the graveyard some stones are protected from weathering by ivy, trees, or even the church itself. This shelter can both help and hinder weathering.
Weathering/Age Index:
In order to judge how badly the stones had been weathered I created a system of grading the stones according to the amount of weathering of certain characteristics such as how faded the letters were. I have graded them 1-5, 5 generally being a low amount of weathering, whilst 1 being a severe amount of weathering. Please see my pilot study for an explanation of why I chose to have 5 different grades and why I have chosen plants to be an aid in the prevention of weathering on the stone.
- Letters: 1 – Not readable: completely faded, all letters missing.
2 – Badly readable; letters missing, very faded.
3 – Just readable; fairly faded, a letter missing.
4 – Fairly readable but has faded somewhat.
5 – Very clear and shows virtually no signs of weathering.
- Cracks: 1 - Lots of both large and small cracks/whole pieces missing.
2 – Lots of small cracks and a few large ones.
3 – Lots of small cracks.
4 – A few small cracks.
5 – Virtually no cracks.
- Exfoliation: 1 – Unreadable/majority of stone missing.
2 – Large amount.
3 – Medium amount/some letters missing.
4 – Small amount/a letter missing.
5 – Virtually none.
- Ivy/Plants: 1 – Virtually no ivy/plants.
2 – Small amount of ivy/plants or very few bits.
3 – Small parts/clusters of plants/ivy.
4 – Most of stone covered in plants/ivy.
5 – Completely covered in plants/ivy.
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Maps:
Fig. 1
These three maps I hope give an
understanding as to the site of the
the graveyard. Fig 1 shows where
the county of Berkshire is in England,
Fig 2 shows the area surrounding Eton,
and Fig 3 is a close-up version of the
area in the square in Fig 2.
Fig. 2
Graveyard
Fig. 3
Techniques And Methods
Definition Of Terms:
Here I have listed some of the more complex geographical words and terms I have used in this coursework. Please note that they are not in any particular order:
- Sedimentary Rocks: rocks formed from sediments laid down under waters.
- Chemical Weathering: break up of the rock by processes such as solution change in the minerals which form the rock.
- Exfoliation: a type of physical weathering common in deserts which results in the outer layers of rock being peeled off.
- Freeze-Thaw: break up of rocks by alternate freezing and melting of water trapped in the joints of the rock.
- Igneous Rocks: rocks which began as magma in the interior of the earth.
- Metamorphic rocks: rocks whose form has been changed by heat and/or pressure.
- Physical Weathering: break up of rocks by processes such as freeze thaw which do not alter the minerals which form the rock.
- Weathering: The breakdown of surface rock by weather without any surface movement.
- Solution: a form of chemical weathering.
- Insolation: heating of the earth’s surface from the sun’s rays; greatest in the tropics.
- Salinized: when soil is made salty.
Techniques Used:
- Planning: I planned my project mainly by using a pilot study to decide what equipment I would need, how many readings to take, whether there were enough of each type of stone, and also to check that my own theories worked such as my rock grade scheme. I also did some research in order to be able to identify each stone and understand the key concepts behind weathering. For this I used both the internet and also a number of textbooks (please see my bibliography)
- Rock grading: I graded the rocks mainly by eye, using my rock grading scheme to help me identify the characteristics of each rock. Furthermore I used what I will call the ‘thumb grade’ technique, a method by which I was able to further identify the rock. It works by sliding your thumb down the edge of the rock to feel how rough or smooth it is; if it is smooth, it is probably had less weathering than if the rock is rough.
- Data collection: I collected it by hand and for this I created a table to store the collected data containing the rock type because this was what I am studying, the age of the rock because older stones will be more weathered, the way it faced because I wanted to see if the direction the stone faced made any difference to the amount of weathering, the weathering grade so that I could judge the amount of weathering on each stone, comments on each stone in case there was anything else interesting about each stone, and finally the rock code/number, so that I could see where each one was on my map according to its code. This code includes a number, which is given in the order I studied the rocks, and two letters, which refer to the area of the grave (e.g. NW, means North West area).
Evaluation Of Techniques:
- I think the planning section of my project went well so that I was prepared for it; I could identify the different rock types and grade the separate rocks; I discovered what to put in my table and what equipment I would need. At the same time I still did not see a few of the most obvious things such as the fact that the ink in my table would run if it rained (which it did). I would have liked further more time to plan my project though. I would have liked, for example, to do an entire mini project first so that I could get an idea of the trends that might occur in this project’s data. Generally though, I think that the planning section of the coursework was successful and helped me understand the concepts of weathering.
- On the one hand I think that the ‘thumb’ method of grading the stones was very effective because it meant that in Granite rocks, for example, that have less obvious visual flaws, I could grade them more decisively. However, on the other hand, the rock grading scheme was not quite as successful, because on some stones it is quite hard to see any visual signs of weathering. Generally though, I thought that my methods of grading the rocks went well because if I couldn’t grade the rock visually, then I used the thumb method which was very effective in combating this problem.
- In terms of data collection, I thought that due to my planning my table was well thought-out and served its purpose very well, although the ink did run in the rain slightly. The only things I would have liked to have improved about my data collection, are that I would have liked to have written more in-depth comments on each stone, but I didn’t have the time do stop and do this for each stone. I would have also like to increase my sample size but there were no more granite stones in the Graveyard and I did not have the time anyway to do any more.
Results
This scatter graph shows the average weathering grade over the age groups. I chose to make the groups span 30 years each because it seemed to give a decent amount of values per group without the group being too general. It seems to show that the front is generally more weathered than the back, although the difference is only very small. Unsurprisingly, it also shows that the older the grave, the more weathered it is.
This scatter graph again shows the average weathering grade over different age groups. Compared to the scatter graph showing igneous rock (see above) it seems that generally igneous rocks are less weathered than sedimentary rocks, although the difference between the two rocks is surprisingly close, although towards the end of last century it seems that igneous rock was particularly less weathered. Note however, again how the back of the stones seems to be less weathered than the front, which is not what one would expect, although again it is only by a small margin (1/2 a grade).
This bar graph helps make a comparison between the fronts and backs of both the Sedimentary and the Igneous rocks. It seems to suggest that Igneous stones are less affected by weathering than sedimentary, shown by the fact that in all age groups both front and back, the igneous rocks
had a higher or equal average weathering grade than the sedimentary stones. Please note the reason there is no bar for the back of igneous graves in the final age group is because they were all flat graves and so they had no back. Again, it seems to suggest that the backs of graves are less weathered than the front, although it is hard to tell since there is not substantial evidence to support this theory.
Analysis:
Using these three graphs, I would therefore say that my hypothesis that Sedimentary stones are more affected by weathering than Igneous ones is true, because as the bar graph shows, in all age groups Igneous stones get a higher weathering grade than Sedimentary ones and while the statistics are only based on an average of all the stones of that age group, it does show substantial difference between the two types. I think that this is due to the actual makeup of the stones, in the sense that Igneous rocks such as Granite seem to have their crystals much more tightly bonded together than sedimentary rocks do. Following on from this, it seems that the structure of Sedimentary rocks, such as sandstone which has a layered structure, is comparatively weak in its structure, as shown in the following picture, which shows an example of exfoliation:
Note that this does not seem to happen to Igneous stones because they have such a strong structure. This is because acid rain affects sedimentary rocks much more than it affects igneous ones because the carbonic acid in acid rain reacts with the calcium in the rocks to give calcium carbonate which is easily dissolved and washed away in the rain, and so sedimentary rocks are weathered much faster than igneous ones.
My second exploration however, into whether the fronts of graves would be more weathered than their backs was not so conclusive; in fact the data seems to slightly suggest the opposite. The only reason I can think that this could be so is that either the public is not very aware and our weather actually comes from the East, or (much more likely) I may have been biased in my judgment of each side of the graves.
Problems Encountered:
There were quite few problems I encountered in all forms and I have listed them here, hopefully with solutions:
- Biased recording of data. While it is hard to correct this set of data now that it has been processed, in the future I would take extra care to make sure I followed my rock grading scheme and not just give the grade according more to personal opinion. Furthermore, I might ask for a second opinion.
- Grading chiseled granite: the problem with chiseled granite is that it is very hard to see any faults or signs of weathering (see picture below). Fortunately I managed to get around this problem by using the thumb method (see techniques) which worked very well.
- Wet Page: Unfortunately, when it rained my ink smudged a little due to the water. On the other hand I did get round this future problem by hence using a pencil.
- Sample size: Whilst not necessarily a problem because I did have enough stones of each type and age, I would have still liked more stones to increase my sample size and thus get a more detailed answer to my hypothesis. Unfortunately there was no way I could get round this problem because I already used every single igneous stone there was in the graveyard.
Conclusion:
Therefore I would conclude that there is sufficient evidence to support my hypothesis that Sedimentary stones are more affected by weathering than igneous stones. On the other I would say that there is not only not enough data to support my exploration into the fact that the front of graves are less weathered than the back, but there is a negative correlation, suggesting that the backs are in fact slightly less weathered.
As a general evaluation, I would say that I think that my project went well and was on the whole successful in proving what it set out to prove, although there were some problems, but which most I overcame. If I had to do such a project in the future I would like more time to plan and research to get more of an idea of what to expect. I would also make sure to give an unbiased view although if not possible I would get a second opinion from someone else.
Bibliography:
Used for images, maps etc.
Used for general research into weathering.
Bowen And Palister ‘Key To Understanding Geography GCSE’ Used again for research into weathering and for key geographical terms
