Tag Archives: Glaciation

Jökulsárlón

As promised, here is another post from my Iceland trip.  This time it’s of Jökulsárlón.  To be honest I don’t know why this place isn’t better known.  For me I think it’s one of the natural crown jewels of Europe, nevermind of Iceland.  Basically Jökulsárlón is a semi-tidal lagoon on the south-east coast of Iceland and formed in the 1930’s by the retreat of Breiðamerkurjökul.  Breiðamerkurjökul’s moraines formed the edge of the lagoon and there is a small tidal river connecting the lagoon to the sea.  But what for me makes this place so special are the icebergs.  Breiðamerkurjökul carves the icebergs which then float around in the lagoon, slowly melting.  Some of them do make it down the small river floating out to the sea, but also being pushed back by the tide and landing on the beach forming yet more amazing ice blocks on the black sand.  OK so that’s enough of me talking lets have some pictures.

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I think the one above looks a bit like a seal’s head.

DSCN3065The pictures really don’t do this place justice.  Maybe I just don’t get out enough but this is one of the most amazing places I’ve ever visited.  I probably will never get to go to Antarctica or the high Arctic, but this is pretty close.  This is one place that should be on a lot of peoples’ bucket lists and I’m glad to have ticked it off mine.

 

Fenn’s, Whixall & Bettisfield Mosses

On a cold but sunny winters day I made what is my second visit this area.  The picture above is from a previous trip when the weather was a lot warmer.  It was still freezing on my visit the other day, despite it being in the middle of the day.
DSCN0641Location & Access: The Fenn’s, Whixall & Bettisfield Mosses straddles the English-Welsh border about 5 miles south-west of Whitchurch.  There is no major road to the site, so you’ll have to take one of the narrower country lanes off the A495, B5476 or B5063.  If you fancy taking a boat though the Llangollen Canal runs through the middle of the site.  The site is relatively flat and shouldn’t provide any problems, though the walk from one of the carparks can be a bit of a trek if you have mobility problems.

Geology: The geology of the area is perhaps less obvious than the hills & valleys I normally write about.  The Mosses are a rare environment, being a lowland raised bog and small areas of wetland it is a unique habitat for wildlife too.  Their formation began about 12,000 years ago as the ice sheets retreated north.  In amongst the till were depressions filled with water and melting ice.  These formed the kettle holes that dominated the north Shropshire, south Cheshire and Wrexham area.  Some of the these holes remained full of water and form the numerous kettle ponds that can be found in the area.  Good examples can be found in Ellesmere and Delamere.  In the case of the Mosses the hole filled up with layer upon layer of peat.  This has created an acidic peat bog that has made a fantastic, albeit soggy under foot, environment and a link to our country’s icy past.

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Wildlife: Besides the peat bog and its like to an ancient glacial past the Mosses is a great place for wildlife…well when its not frozen over ;).

Alongside the myriad of insects and spiders there are also adders and a wide range of birds, and according to one local I spoke to, the rarely sited water shrew.  Unfortunately due to it being winter I didn’t see most of these.  I did manage to get some pictures of the water fowl in the area.

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These are my first attempts at photographing flocks of birds in flight.  I had mixed results with many of pictures focusing on the background rather than the birds, but I don’t think they’re too bad for a first timer.  The ducks that I’ve managed to get shots of include Shovelers (Anas clypeata), Wigeons (Anas penelope), Teals (Anas crecca) and Mallards (Anas platyrhynchos).  I also saw some Pintails (Anas acuta) and Lapwings (Vanellus vanellus) but happened to be changing the battery at the time.

References: Fundamentals of the Physical Environment (3rd Edition) by P. Smithson, K. Addison & K. Atkinson (2002).  Geology (2nd Edition)by S. Chernicoff (1999).  Geology of Shropshire (2nd Edition) by P. Toghill (2006).  The Geology of Britain – An Introduction by P. Toghill (2006).   iGeology map from the BGS (2015).  Information leaflet from the site and produced by Natural England and Cyngor Cefn Gwlad Cymru (Countryside Council for Wales).

 

Ingleborough Cave

Time for my second post of my Yorkshire Dales trip.  As I alluded to in my last post about Malham Cove, one of our goals for the trip was to visit Gaping Gill.  Sadly this wasn’t open due to a technical fault, so instead we visited the nearby Ingleborough Cave.  One thing to note is that this isn’t a potholer’s cave, it’s a show cave.  My own potholing experience amounts to a trip down an abandoned slate mine in Wales…anything more adventurous and I’m likely to become a troglodyte.  Oh and apologizes for the quality of some of the images, it’s a little hard to take photos in the dark cave light.

Location & Access: To get to the cave, park in the village of Clapham, just off the A65.  The cave is about 2km north of the village located around 54*08’05” North, 2*22’38” West.  To get to the cave you follow the path north out of the village.  The path is wide and in very good condition (rather bizarrely a toll path too so bring some pennies), so you shouldn’t have to much trouble walking to the cave.  Sadly there is no closer public vehicular access, so you’ll have to walk.  Being a show cave, Ingleborough Cave is geared towards families, the access is good and the cave floor has been given a layer of concrete to allow disabled usage.  This doesn’t spoil the aesthetic to much.  The tour of the cave does involve a guide and will cost money some bring some cash.

Geology:  The cave is in the bedding planes of the Garsdale Limestone Formation (331-339Ma) and like Malham Cove it was once a shallow, carbonate sea.  In some places you can actually see the fossils of the coral and other organisms.

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The cave was carved out by river water and was partially filled in by glacial till, some of which has been removed to open up the cave.  Not all of it has been and the full extent of the cave is not yet know.

IMG_2206Excavations are still on going and have brought up the remains of a woolly rhinoceros tooth, from the Devensian Glaciation (about 10,000 years ago).

There are several underwater pools still in the cave, and the cave itself is regularly flooded when there are heavy thunderstorms.  When the cave was first explored in 1837 it was flooded, the water held back by a calcite dam.  This was blasted to drain the lake at the time, but parts of another calcite dam can be seen.

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The historic level of the cave water is marked out at a level where you find the cave coral deposits below the waterline and the flowstone above.

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There are plenty of stalactites and stalagmites in the cave of various sizes, the biggest of which is The Sword of Damocles and is a few metres long.

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Along with these you will see plenty of helictites and speleogens as well as other cave formations.  A look at the feature image to this post shows how the natural cleavage & faults in the rock are exploited by the water and form the basis of the stalactites.

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Overall this a good cave to visit, especially if you are not an experienced caver, and a good alternative to Gaping Gill if the winch is broken.  It’s a show-cave, but a good one.  There are plenty of formations to see, and if you are in the area I would recommend visiting the cave if you have a spare couple of hours.  They also have a good website explaining the cave and showing more pictures at www.ingleboroughcave.co.uk.

Reference: The Geology of Britain; An Introduction by Peter Toghill (2006), Geology (2nd Edition) by Stanley Chernicoff (1999), http://www.ingleboroughcave.co.uk and the tour guide on the day.

Malham Cove

This week I have had the opportunity to visit the fantastic Yorkshire Dales in the north of England.  I got a chance to visit a few sites.  Much to our disappointment we weren’t able to get down Gaping Gill due to a technical fault with the winch, so we instead saw a few other places and I’d thought I’d share them with you.  The first is epic Malham Cove.

Location & Access:  Malham Cove is located in the south half of the Yorkshire Dales National Park at approximately 54*21’41” North, 2*09’28” West, about 1km from Malham village.  You can park a car in the village (itself a wonderful place to see) and walk up the road to the cove.  The road is good and there is a slight incline.  just above the village is a clearly marked, good quality path to the cove…and to be honest you really can’t miss it from there.  People with mobility issues shouldn’t have much trouble walking along the path, though the road can be a bit of a trek.  Warning!  The main path goes through a field of cows so beware of bovines.

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Geology:  The underlying rock is Carboniferous Limestone from the Garsdale and Danny Bridge Formations (331-339Ma), and represents a depositional environment of a shallow carbonate sea, full of corals and shell creatures.  That was then, what about now?  Like much of northern England the current landscape is largely the result of the various glaciations of the past, in particular the Devensian glaciation which ended about 10,000 years ago.  Malham Cove is thought to have been formed slightly earlier (about 12,000 years ago) as the ice retreated north.  The melting glaciers produced a large amount of run-off, and with the ground still being semi-frozen permafrost the water eroded the limestone instead of infiltrating into and dissolving it as happens now.

This led to the wonderful dry water seen today.  The semi-circular Malham Cove is about 80m high and about 300m across.  This makes it higher, but only about half as wide as the horse-shoe at Niagara Falls.  This gives you an idea of what the falls would have looked like in full flow 12,000 years ago.

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IMG_2331You can see the bedding planes in the limestone and if you look at the right of the image above you should be able to see two climbers ascending the cliff face (right of the centre tree, about half way up the picture in yellow).  This gives you an idea of the scale of the place.  At the base of the cliff is a small stream, exiting from one of the many underground river systems in the Dales.

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Although you should always be careful approaching a cliff face I would recommend getting as near to the base as possible and looking up…it’s fantastic.  I tried to take a few pictures, but none of them do it justice, so you’ll just have to go there yourself.  Stand in the centre of the horse-shoe, close to the base and look up, it’s this wonderful bowl shape.

Above the falls is another wonder of the Dales; the limestone pavement.

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These are a special feature, common to the Dales, but rare in the rest of the UK.  The flat surface is a bedding plane in the limestone, exposed by glacial & periglacial erosion.  This produces the flat ‘paving slabs’ called clints.  The gaps in between are the result of rain water getting into cracks in the limestone and dissolving some of it.  These gaps are called grykes.  Walking along a limestone pavement is quite an experience, but be warned some of the clints are wobbly and the grykes can be wide and deep.  Some of them may even be filled in with a thin layer of soil & grass so watch your step.

Other Stuff: You’ve got glacial valleys & erosion, caves, underwater rivers & springs, a dry waterfall higher than Niagara and limestone pavements…what more could you want? OK well aside from the geology it is also a great pace to catch a glimpse of one of my favourite birds; the Peregrine Falcon.  These nest up on the cliff face your chances of seeing one is good.

To sum up, if you are ever in the north of England Malham Cove is worth the visit.  The pictures I’ve posted really don’t do it justice, you’ll have to go see it for yourself.  Stay geogeeky as I’ve got more from the Dales that I’ll post soon.  Enjoy.

Reference: The Geology of Britain; An Introduction by Peter Toghill (2006), Geology (2nd Edition) by Stanley Chernicoff (1999).

 

 

Geological Time Part 2 – The Periods in Shropshire

As part of my geological time series I thought I’d have a look at where rocks/features of the periods can be found in Shropshire.  Shropshire is a very geologically diverse county and if you look hard enough you can find examples from all of the time periods except for the Cretaceous (though the Tertiary is a little dodgy) .  I will say that the examples I am giving are not the only ones to be found in the county.  There are many other formations, rock types and sites that can be used to represent the time periods, I’ve just pick a selected few.  So prepare for a few explanations and quite a lot of pictures.  Just as a remind ma stands for millions of years ago.

Shropshire’s Geological Timeline

Shropshire Geology Time 2

Shropshire Base Map 1

 

I’ve included a brief timeline and a small map giving the rough location of the sites I visited (blue circles) with the major towns in the county for reference.

Quaternary Period (2ma to present)

As we are still living in the Quaternary then many landforms can be seen to represent what has and is still going on in the county.  For a more pre-historical landform a good example would be the glacial relics, of which the kettle holes and peat bogs around Ellesmere would be a good place to start.

DSCF2941DSCF3579These features were formed after the ice of the Devensian Glaciation retreated around 11,000 years, leaving layers of sand and gravel (commonly called glacial till).  The kettle hole forms when a block of ice falls of the retreating glacier and melts, leaving a water-filled depression.

Neogene, Paleogene and Cretaceous Periods

Sadly these formations are missing from Shropshire.  There is rumour of a Tertiary (possibly Neogene) outcrop near Whitchurch, but I haven’t been able to confirm it and I can’t find it on a map, so for now it’ll have to remain a mystery.

Jurassic (200 to 145ma)

You’ll be lucky to find this one.  There is only one real outcrop of Jurassic age rock in the county and that is around the village of Prees, about 5 miles south of Whitchurch.  There is some Jurassic bedrock under the layers of glacial till, but Prees is the only place it comes to the surface.  You can see one exposure, just east of the A49.  To get to it you can follow a public footpath.  The rock is mudstone from 183-190ma and the environment was once a shallow, tropical sea.

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Triassic (252 to 200ma)

The Triassic and Permian are both present in Shropshire, but the exact boundary has caused a little confusion in the past.  This is largely down to the similarities in the formations and the fact that they rest one on top of the other in the same locations.  Personally I think the best place in the county to see both Triassic and Permian is around Bridgnorth, though there are some other impressive red-rock formations that form several ridges in the north of the county.  The Triassic rocks are to the east of Bridgnorth, further up the hill and form part of the Kidderminster Formation.  It is mostly made up of red sandstone and conglomerate.  The image below is that of an exposure on the A442 near Allscott, just north of Bridgnorth and shows a layer of conglomerate sandwiched between two layers of sandstone.  It is a good example of cross-bedding between the strata and is representative of a river running through a desert environment.

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Permian (299 to 252ma)

As I said in the Triassic section, Bridgnorth is the place to see Permian rocks, in fact most of the town is built on it and some of the older buildings are made from it.  The Permian sandstone is also red, shows cross-bedding as the result of wind-blown desert sand, but seems to be a little tougher.  My Triassic samples half crumbled as I was extracting and transporting them.  Again the ancient environment was a desert.

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Carboniferous (359 to 299ma)

For the Carboniferous Period I’ve chosen something a little special; the Tar Tunnel.  Unlike my other choices this is something of a minor tourist attraction and as such will require the parting of a couple of coins.  It’s found in the east end of the Ironbridge Gorge.  The rock in the surrounding area is a mixture of limestones, coals, sandstones, mudstones, and conglomerates from the late Carboniferous Period.  When the Industrial Revolution was in full swing in Ironbridge a tunnel was built to act as short cut between the mines and the River Severn.  Upon digging the tunnel the walls started to ooze natural bitumen.  This was then extracted for a number of years before the industry moved on.  Is there likely to be an oil rush in Shropshire?  Not likely but it is an interesting phenomenon and one that I don’t think can be seen anywhere else in the UK.  If like me you are a ‘geo-geek’ it’s worth seeing.

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If it was red you’d think you were in a cheap horror movie.  The image below shows an pool of tar in a side chamber.

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For a more mundane sample from further up the gorge (Jigger’s Bank) you can see an exposure of the Lydebrook Sandstone.  This layer is made up of a pebbly sandstone and includes layers of conglomerate, and was what I used in the geological timeline above.

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Devonian (416 to 359ma)

Devonian rock actually forms the bulk of Shropshire’s tallest hill; Brown Clee Hill (not to be confused with the neighbouring Clee Hill or Titterstone Clee Hill).

Below is an image of Brown Clee Hill taken from the Wenlock Edge.

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Silurian (443 to 416ma)

The Silurian is very well represented in Shropshire.  One of the best formations in the county (and possibly the country) to see rocks of Silurian age is the beautiful Wenlock Edge.

The Edge is an escarpment that runs for almost 20 miles in a north-east to south-west direction and is made up of of a knoll-reef limestone with lime-rich mudstones & shales surrounding it.

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There are numerous walks along the Edge and due to the old (and current) quarrying activities there are plenty of places to see the local geology.  The above picture showing some wonderfully defined bedding planes.  It is also a good place to go fossil hunting.  There are several places both on and under the Edge were you can collect some nice samples like the one shown below.

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Ordovician (488ma to 443ma)

Like the Silurian the Ordovician Period is well represented in Shropshire, but I’m going to go for a well known formation; the Stiperstones Hills.  The Stiperstones are made up of quartzite and like the Wrekin Quartzite is a misnomer as it is a hard, white sandstone and not a metamorphic rock (like true quartzite is).  The Stiperstones have the added advantage that besides the Ordovician rock, you also have the tors formed from millennia of ice/frost shattering.

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Cambrian (542ma to 488ma)

The Cambrian witnessed a massive diversification of animal lifeforms (often called the Cambrian Explosion) and there some good locations and rocks to be seen in Shropshire.  The Ercall quarry has some wonderful quartzite to sandstone formations, showing beach ripples, conglomerates and inclined strata (see my Ercall post for more)

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The Wrekin Quartzite gives way to the Comley Sandstone.  The type site is the sadly neglected Comley Quarry (located on the north-east slope of Caer Caradoc) where Shropshire’s first Cambrian trilobites were found.  Unfortunately the rock faces are now overgrown and difficult to see.  It can be seen in better condition a the Ercall.

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Precambrian (4600ma to 542ma)

Being such a long eon the Precambrian goes from the formation of the earth to around 542ma.  The Precambrian rocks in Shropshire are mostly from towards the younger end; around 570ma with the gneiss and schist of Primrose Hill possibly being older.  My choice for the Precambrian is the Uriconian Volcanic formation which makes up a number of hills, including the Wrekin, Caer Caradoc and the Lawley.

This photo was taken from the Long Mynd (itself a sedimentary formation from the Precambrian) showing Caer Caradoc (centre right), the Lawley (centre left, and a bit in the distance) and on the left horizon is the Wrekin.  These hills are made up mostly of rhyolite, andesite and basalt.

Below is a sample of basalt from the Wrekin.

IMG_1862Well there you have, a brief geological tour of Shropshire.  The county has seen volcanoes and beaches, deserts and tropical seas and now the efforts of an enthusiastic geo-geek.  Hope you enjoy.