Introduction
I enjoy learning about geology but oh crikey there are such a lot of new words to learn! 😄
Just reading a book, paper or article sometimes sees me spending more time googling words or looking them up in a dictionary than I spend actually reading and trying to understand and inwardly digest the information 😂
Fortunately I've managed not only to learn but actually retain a new word which comes in pretty useful - and that word is ferruginous.
Ferruginous is a word used to describe substances which include oxides of iron in their makeup. The iron oxide that most people know and recognise is commonly known as rust, and is typically found on ferrous metals, but the iron oxides this EarthCache relates to are found in a sedimentary rock, namely sandstone.
Logging Tasks
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Based on your observations at the two cache locations and the information on the cache page, please tell me:
- Describe the ferruginous features in the sandstone of the building at the published coordinates
- Describe the ferruginous features in the sandstone wall cladding (below the glass) of the building at Stage 2
- Describe the ferruginous features of the paving slabs beneath your feet at Stage 2
- List any similarities / differences you notice between the three sets of ferruginous sandstones
- At Stage 2, embedded in the sandstone wall cladding, there's an obvious dark brown deposit which reminded me of a pointed tooth or fang. This deposit is clay and is much smoother than the surrounding sandstone because it's made up of much smaller grains. How long is it? (Hint - if you don't have anything to measure with, take a photograph of your finger alongside the feature and use it as a scale to measure back at home, or put a piece of paper next to the feature and mark its length on the paper and measure that back at home
).
- Optional task: feel free to add any photographs of your visit that do not show the specific features from the logging tasks - no spoilers please. In the interests of allowing everyone to experience the EarthCache fully for themselves obvious spoiler photographs will be deleted.
Background
I like words and I like to look up their origins or etymology 🧐.
Ferruginous, it turns out, originates from a latin word with an anglo-norman French suffix stuck on the end. Ferrum is the latin word for iron; ferrugo and ferrugin mean rust and dark red respectively.
Take ferrugin and stick the suffix ous on the end and you have ferruginous, literally characterized by the presence of dark red.
Iron oxides though don't always appear, in nature at least, as dark red substances. Iron oxides in rocks typically range from yellows through oranges and browns to pinks and deep reds - depending largely on their level of concentration within the rock.
Ferruginous features in rocks can reveal information about where and how those rocks were originally formed, as well as processes that the rocks underwent after they were formed.
This EarthCache takes you to a couple of locations in the centre of Manchester where you can see ferruginous sandstones. Your task is to compare the ferruginous features found at the two locations and describe their appearance and nature, accurately and in some detail.
There's probably lots of ways to describe the nature of these ferruginous features scientifically but there are definitely simple, practical ways too - so let's look at some examples:
Colour
The most basic property we can use to describe the rocks and any ferruginous features within in them is colour - or colours.
Ferruginous rocks commonly feature a range of colours / shades including yellows, beiges, pinks, browns, oranges and reds.
Concentration / Intensity
The intensity of colours found in ferruginous rocks arising from the included iron oxides varies according to the amount of oxides present in any particular part of the rock - the concentration.
Artist's watercolours offer a simple analogy here. Starting with pure water, the more pigment added by the artist, the more intense / concentrated the colour becomes.
By precisely combining water and pigment in particular proportions the artist can produce a whole range of tints and shades, from soft, muted, pale combinations to more vivid, intense variations.
Distribution
If the ferrous oxides in a rock are distributed evenly throughout the entire rock then the colour is likely to be even and consistent throughout. In other words, if the amount of ferrous oxide is the same everywhere, the colour will be the same everywhere.
If the amount of ferrous oxide varies in different parts of the rock the colours or their shades / intensities will vary too.
Variations may appear as smooth gradients, as isolated patches of colour, as bands, spots, arcs, arches, geometric patterns or myriad other combinations.
One reason that sandstone is such a popular building stone is the beauty imparted to the rock by the variable and often abstract patterns of minerals and oxides.
Colouring outside the lines
A fairly common feature of sedimentary rocks is that they tend to be laid roughly horizontally in bands which geologists call beds. Beds are one type of structural feature of the stone. Structural features are visible by virtue of the way they affect the arrangement of grains in the rock. Sometimes structural features, fractures for example, can affect the concentration of ferrous oxides in the rock. Sometimes though, the arrangement of ferrous oxides bears no correlation whatsoever to structual features.
Bands of ferrous oxides might conform to bedding planes or fractures in the rock, or to forms created by the soft sediments being disturbed before they were compressed and cemented together into solid rock - ripples caused by moving water for example. Equally though, bands might form in seemingly random patterns, completely unconnected to structural features.
Bands might be straight and parallel or form sweeping curves, rings, zig-zag patterns or completely abstract arrangements. They may be thin or thick, continuous or broken, light or dark etc. etc.
If you've carefully read and digested the information from this cache page your tasks at the cache location should prove relatively straight forward, although you may wish to take a printed copy of the page with you so that you can check your answers while there .
Please submit your logging task responses before posting your log.