North Sea Geomorphology

Many of us are familiar with making small-scale macro and micro geological observations on field trips and in labs, peering curiously (we hope) at bedding planes, grain boundaries, fossils and outcrop structure. However, it is equally as important to take a step back and consider how these minute details impact on the landscape and topography around us. Here in Britain, we are lucky to have incredibly diverse geology in a relatively small area, and these large scale mega observations* can prove pretty valuable in plotting out large scale features, such as major fault lines and distinct changes in rock type or structure.

Along with old-school paper maps, this is where Google Earth really comes into its element. Being able to see aerial imagery along with elevation and alternative viewing angles means you really can explore the world from your desk (or even sofa). So, carrying on the theme of the exotic, we’re off to Hull.

Photo Friday: A lava-lee waterfall

 

For today’s installment we’re flying off to Iceland once more, and to Seyðisfjörður in the east of the country. It also manages to capture the famous saying of ‘the land of fire and ice’ pretty well, with snow lying immediately on top of numerous repeated lava flows. (This photo was taken in July too – it’s quite nippy this far north!) We geologists always need a scale in our photos, so if you have a look at the electricity pylon at the bottom right you get a good idea of the scale of this scarp! We also love a bit of differential weathering, and I love how the stream has zig-zagged its way down each individual lava flow, always after the path of least resistance – I’m sure we can all relate sometimes!

Happy Friday!

Geopolitics in action: Exploring planet oil

As we all know, I’m a sucker for a good documentary, even those that aren’t related to geology.

However, this time around the subject couldn’t be more relevant; falling prices, conflicts in the Middle East, debates about sustainability and the implications of fracking all mean that oil is the hot topic du jour.

In a three-part series, professor Iain Stewart explores the history of our global addiction and reliance on oil, and how it has altered economics, politics and our environment in a timespan little over that of a human lifetime.

http://www.bbc.co.uk/programmes/p02gzf9k

Happy watching!

Calling all volcanologists!!

 

Here is yet another Icelandic photo, and probably of one of the more photographed expanses of cliff on the island (maybe in the world?) However, this one has me baffled!

Now, we can all see the columnar jointing in the basalt, and there is clearly a relationship between it and the large, dark section at the centre of the outcrop. The thing that stumps me is what the relationship could be between the basalt and the blob (I promise I can be more eloquent sometimes!

If anyone could help me out, I would be much obliged!

 

Flying visit to the Scilly Isles

Carrying on with Friday’s theme of rooting through old photos, I thought I’d share a few from a family trip to the Scilly Isles way back in 2008.

Aerial view from the incoming helicopter

I mentioned in a previous post the great Cornubian Batholith, an enormous granite body that makes many appearances across the south-west of England. The granite was emplaced during the Late Permian, as part of the later stages of the Variscan Orogeny. As well as the many tors of Devon and Cornwall, one of these outcrops is the characteristic archipelago of the Scilly Isles, a scattering of islands clustered beyond Land’s End. Up until around 500 AD (a mere blink of an eye from a geologist’s perspective), the islands were one large outcrop, before rising sea levels split it into around fifty-five separate islands and islets.

Out of these fifty-five, only five of the islands are currently inhabited: St Mary’s, St Agnes, St Martin’s, Bryher and Tresco. At extreme low tides it is also possible to walk (or at least paddle!) between some of the islands, and the relatively recent sea level rise means that ancient field boundaries are also exposed by the receding water. From above, the Scilly Isles look like a tropical paradise, with their isolated white sand beaches. At times you could be forgiven for the mistake, as the westerly position of the archipelago means that they are exposed to the warming effects of the Gulf Stream. However, it is far more likely that it is due to the high quartz content of the eroding granite!

Now, these photos are from a looong time ago, so apologies for the rather dodgy nature, but I thought I’d provide a quick overview of my time in paradise!

Incoming swell at the appropriately named Hell Bay

Photo Friday: From up above

 

Domestic flights across Iceland are definitely worth bagging a window seat for!

 

Under the microscope

After a little hiatus last week, (I think I’m still working off the post-Christmas cheese hangover) I’m back with some images of a slightly different type. Although it can be said that a large proportion of geoscience study can be conducted using large scale observations and “in hand” specimens*, the microscope is an invaluable tool, even to us geologists who prefer sturdy boots to lab coats.

Once a rock is cut into a 30µm thick slice, known in the trade as a “thin section” (imaginative, I know), a whole new world of information opens up as soon as it is put under a microscope. A vast amount of knowledge can be gained by looking at a chunk of rock in your hand, but being able to make crystal-scale observations can mean access to the next level of information on mineralogy, post-depositional processes and structure.

Thin sections can be viewed in two ways; under plain polarised light (PPL) and crossed polarised light (XPL), which highlights the optical properties of individual minerals and allows for easy (ish) identification. In the interests of curiosity, I’ve got examples of both.

Photo Friday: When mountains collide

 

If only all outcrops were this exposed and obvious eh! For this weeks photo Friday here’s a lovely little exposure of some metamorphic gneiss, which just so happens to have fractured and broken off to provide the perfect cross section!

Photo Friday: China Clay and Cornish Fog

 

Here we have a photo from a fieldtrip way back in 2012 to Cornwall, the most southwesterly county in England. This is taken from the viewing platform at the Wheal Martyn china clay mine with some atmospheric fog and mist as a free gift (the fog didn’t actually lift for the whole week we were in Cornwall, so we never got a half decent view of one of the most beautiful areas of Britain).

Photo Friday: My First Fieldtrip

For a special treat I’m delivering a winning combo of a Throwback Thursday and a Photo Friday, and today’s exotic location is the Isle of Arran, on the west coast of bonnie Scotland (not to be confused with the Aran Isles off the coast of Ireland).

Arran is a bit of a Mecca for geologists, as it has an enormous variety of lithologies and geological processes packed into a relatively small area (it’s about an hour’s drive top to bottom).

Mafic dyke stretching out to sea, illustrating the difference in resistance between Palaeogene basalt and Triassic sandstone

 

I first encountered Arran’s geology way back in 2010, being the destination for my AS and A-Level geology field course (for non-UK readers this is age 16-18).

It goes without saying that Arran is one of the best field locations to study the law of cross-cutting relationships, as there are numerous outcrops illustrating the relationship between the metamorphic, sedimentary and igneous chapters in Arran’s history.