Introduction
The Sir John Barrow monument, also known as the Hoad Monument and colloquially as the pepperpot and the lighthouse without a light, is a 100 foot tall Grade II* listed building which sits atop Hoad Hill, overlooking the town of Ulverston.
Hoad Hill affords glorious views over Morecambe Bay, the Langdales and the Yorkshire Dales, so while it's a bit of a stiff climb on a hot day, despite the zig-zagging route of the well-trodden paths which meander to the summit, it's well worth the effort for the views from the top.
The monument is easily recognisable from a considerable distance due to its elevated position, its height and the fact it looks like a lighthouse - but the truth is that it has never been used as a lighthouse. Rather its form arises from its purpose as a tribute to a local man who rose to high rank within the British navy.
The laying of the foundation stone by Sir John Barrow's two sons on 15th May 1850 reportedly drew an audience of some 8,000 citizens.
Continuing the marine theme is the rock that the monument is made of - local limestone from nearby Birkrigg Common - where there's an opportunity to add another EarthCache find to your tally if you so wish.
What's perhaps most appealing though, to those with an interest in things geological, is the presence of fossilised sea creatures in some of the tower's limestone and in the ring of limestone flags, laid as a footpath encircling the base.
The monument is open to the public when the flag is flying - usually on Sundays and Bank holidays between Easter and the end of October (weather permitting) between 1pm and 5pm, affording the opportunity to climb the 112 steps of the spiral staircase to the lantern house. Entry is free. Donations are welcome.
There is no need to enter the monument in order to complete the EarthCache - everything you need to see is on the outside.
Logging Tasks
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Based on your study of the exposed limestone at the base of the monument and the circular path of limestone flags encircling the base, and using the information on the cache page please tell me:
- Describe the limestone blocks used in the base of the monument. Which type of limestone do you think they are carved from and how do you arrive at this conclusion?
- Describe the limestone slabs which form the path around the monument. Is the same limestone used in the base of the monument? (Give at least two reasons why you think this - more if you can).
- Describe which types of fossils you see and where?
- Please provide a photograph of yourself - or a personal item - in front of the monument as proof of your visit.
- Feel free to include with your logs 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
The bedrock of the hill itself is sandstone - specifically a member of the Bannisdale Formation, laid down approximately 424 to 427 million years ago.
Sandstone may bring to mind a rock in some shade of beige which, under closer inspection, reveals that it's made up of grains of sand such as one might find at the beach - and that's partly true.
What I've learned though, is that what makes a sandstone a sandstone is more about the size of the grains than anything else. Sandstone is made up of sand sized grains and, according to geologists, sand sized grains range from 0.0625 to 2mm in diameter.
So why am I waffling about sandstone and sand sized grains when the subject of this EarthCache is limestone? Read on to find out! 😁
Park Limestone & Urswick Limestone - Calcarenites
One significant challenge facing we amateur geologists is just reading about the stuff - so many new words and terms to learn simply in order to understand a given text or article 😯.
An arenite is any sedimentary rock that consists of sand-sized particles, irrespective of composition.
A calcarenite is a type of limestone that is composed predominantly (more than 50 percent) of detrital (transported) sand sized (0.0625 to 2 mm in diameter), carbonate grains.
There are those dimensions again - those sand sized grains - which means that a calcarenite may look similar to a sandstone - at least in terms of the size of the grains it is made of - although probably not in colour.
And why is calcarenite important here? Because the limestone the monument is made of came from nearby Birkrigg Common, a source of Park Limestone and Urswick Limestone - both of which are calcarenites.
In fact, if we were being picky:
- Park Limestone is an unbedded or poorly bedded, pale grey or pale yellowish grey bioclastic and peloidal grainstone or biocalcarenite.
- Urswick Limestone is mainly thickly and well-bedded pale grey grainstones or calcarenites, commonly with darker mottling (pseudobreccia) and a rubbly texture.
In plain English? These limestones are made up of sand sized fragments of the skeletons and shells of dead sea creatures, stuck together (weakly in the case of the Park Limestone and strongly in the case of the Urswick Limestone).
Geologists believe that Park Limestone formed in deeper water and this led to it being poorly bedded and weakly cemented and thus not especially tough. At Birkrigg Common, right next to the Park Limestone there's a whole bunch of Urswick Limestone which is well bedded and cemented and so much tougher and a much better candidate for a resilient building material.
These two limestones are both from the Carboniferous Period and were laid down around 330 million years ago, making them roughly 100 million years younger than the sandstone bedrock of Hoad Hill.
Today, much of the limestone the monument is built from is hidden from view by a layer of cement, applied in a bid to make the structure watertight, and so the focus of this EarthCache is limited to the stone at the base of the monument to a height of a couple of feet and to the footpath of limestone slabs around the perimeter of that base.
What is a fossil?
Fossils are the preserved remains of plants or animals. For such remains to be considered fossils, scientists have decided they have to be over 10,000 years old. As the Carboniferous Period ended almost 300,000,000 years ago, any plant or animal remains in Carboniferous limestone definitely qualify as fossils 
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There are two main types of fossils, body fossils and trace fossils. Body fossils are the preserved remains of a plant or animal’s body. Trace fossils are the remains of the activity of an animal, such as preserved trackways, footprints, fossilised egg shells, and nests.
Time to look at some of the types of fossilised sea creature commonly found in limestone...
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Colonial Coral - Corals still inhabit our oceans today and at first glance, you may think that coral reefs are made up of rocks, but they are actually made up of tiny living organisms called polyps.
Some coral polyps build hard carbonate skeletons and also reproduce by making lots of copies of themselves, so that what starts off as a single coral polyp gradually grows into a whole community, with each polyp adding to the growing mass of carbonate material.
If you see a coral fossil in carboniferous limestone you're seeing the hard carbonate material left behind by the many polyps which built it millions of years ago.
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Solitary Coral - In some species of coral the polyps do not form colonies and instead remain as solitary organisms.
Coral polyps are essentially tube-like structures which can range in length from a few mm to as much as 30cm. The tube has a mouth at one end with poisonous tentacles which trap food from the water. There's no anus though - any waste products from the food consumed have to be regurgitated back out through the animal's mouth 🤮.
Fossils of solitary corals tend to be obvious due to being at the larger end of the spectrum and might be described as sausage-shaped.
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Gastropod - from the Greek gastér meaning stomach and podòs meaning foot - so you could call them stomachfoots .
Gastropods belong to the same family as snails and there are thousands of species still alive today. Over millions of years gastropods have evolved to be able to live in all sorts of environments. There are species which live in sea water, others which live in fresh water and still others which live entirely on land. You may have snails in your garden. Those found as fossils in limestone though will almost certainly have lived in the sea 
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Sea snails, at least adult ones, usually have coiled or spiral shaped shells - which makes their fossils very easy to identify.
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Oyster - is the common name for a number of different families of salt-water bivalve molluscs.
Bivalves have two shells or valves, a left valve covering the left hand side of the body and a right valve covering the right hand side of the body. The valves are joined together by a ligament which allows the valves to open up, so the creature can feed for example, or close tightly together to protect the soft body from predators or to retain moisture when out of the water, at low tide for example. This ligament though decays when the creature dies and so the two valves are rarely fossilised together.
If you've ever seen a cockle or a mussel at the seaside or at the local fishmonger's stall, you've seen a bivalve.
Bivalves have inhabited the Earth for over 500 million years. They first appeared in the Mid Cambrian, about 300 million years before the dinosaurs.
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Brachiopod - a modern Latin word derived originally from the Greek brakhion meaning arm and podòs meaning foot. So if we think of gastropods as stomachfoots we might think of brachiopods as armfoots .
Brachiopods get their name because they have two muscular arms which they use to collect food.
Brachiopods have two valves or shells, just like bivalves but where bivalves have a left valve and a right valve which tend to be a mirror image of each other, brachiopods have an upper valve (which covers the upper side of the body) and a lower valve (which covers the lower side of the body) - which are not symmetrical.
In brachiopods one shell is larger than the other which has led to them being commonly known as lamp shells because they resemble early Roman oil lamps.
Brachiopods have existed for around 550 million years and at one time were one of the most abundant forms of life in the sea. The fossil record includes around 12,000 individual species but most of them became extinct a long time ago.
It isn't too difficult to identify brachiopod fossils in cut stone but they can be different shapes depending on the direction of the cut made when the rock was quarried - which is why there are two images to the right showing the most common shapes to help you recognise them.
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Crinoid - also known as sea lilies because some species look more than a little like the flowers of the same name (as shown in the image to the right of a rare fossilised crinoid in which the soft parts were preserved as well as the hard parts). The ancient Greeks must have thought so anyway because crinoid is from the Greek words krinon and eidos which together translate roughly as lily form or lily shaped if you prefer.
Crinoids are very much animals though and definitely not plants. Though crinoids appeared in the Ordovician (488 mya), they survived the Permian mass extinction and diversified into hundreds of species which survive, today.
Crinoids can very basically be described as upside-down starfish with a stem. The stem of a crinoid extends down from what would be the top of a starfish, leaving the mouth of the organism opening skyward, with the feathery arms splayed out to catch any passing food particles. At the bottom of a crinoid stem there's a part called a holdfast which helps to anchor the crinoid to the sea bed.
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Typical crinoid fossil appearance - so the only parts of crinoids that are fossilised most of the time are the hard parts - the ossicles of carbonate material which, in life, are stacked one on top of the other in the long stem. Because they are little tube-like structures with a hole through the middle, some people think that they look like polo mints - the ossicle in the top-left corner of the image on the right is a good example of this.
If you're lucky enough to see a cylindrical stack of articulated ossicles that haven't been cut through, the narrow grooves around the cylinder make the stack look a bit like a bolt or a screw - which is why people sometimes call these fossils screws
More often than not though, when the limestone is cut into slabs the saw blade cuts through the length of any articulated stacks of ossicles, revealing the inside parts and you get what looks a bit like a zip with two rows of jagged teeth pointing in towards each other - like the example toward the right-hand side of the image to the right.
Sometimes you'll see crinoid fossils which have more of a pointed oval shape. This happens when the rock is cut into blocks or slabs and the saw blade cuts through the fossil on an oblique angle.
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.