Through The Sandglass

The Great Sand Dunes – as seen through the lens of ‘Written in Stone’

 

Earlier this year, I discovered a superb geological and photographic blog that I had not encountered before. ‘Written In Stone…seen through my lens’ is by Jack Share, who describes himself as follows:

I was the kid in the Jackson Browne song “in ’65 I was seventeen”, when my educational efforts were directed toward a degree in zoology and a career in the health professions. Years later, the fossils I found as a kid in Central New York led me to paleontology, their evolutionary relationships and to developmental biology. It wasn’t long before I came to appreciate the importance of an education grounded in geology. Former life and former landscapes are indeed inseparable. In this blog I offer an interpretive and photographic perspective of our world, both past and present, and both within my New England home and well beyond.

Jack wrote to me about his two posts on the Great Sand Dunes of Colorado, the first a comprehensive geological review (the ‘the juicy geological details’), the second a photographic essay, ‘Climbing the geology of the dunes.’ I thoroughly recommend a visit to these posts – and to the rest of the blog. Jack has a natural ability to write clearly and informatively but also to make geology fun, and his photographs are great. As a lure, here is a selection (reproduced with his permission).

Guest post: The 'sandwave' - a homage to Elvis?

John Lackie writes:

Last year I had the pleasure of going on a four-day residential field course as part of an Open University geology module (SXG288); one of the sites we visited had a spectacular feature that might be of interest to those who appreciate sand in all its forms.

The site was Bowden Doors in Northumbria (NU 072323), a long, west-facing crag of Fell Sandstone, 3-8m high, a favourite of both climbers and geologists. The sandstone is derived from the erosion of rock above what is now the Southern Uplands of Scotland and the sand was carried south-eastwards by a braided river system during the early Carboniferous period. There are several unusual geological features that I won't reveal (to avoid spoiling future visits by OU students), but the thing that impressed me most was the 'Sandwave'. I was sure Michael would know of this - but he didn't and he invited me to write a guest blog about it.

Inevitably the pictures I had weren't suitable so I revisited the crag some months later: once home I discovered that none of the pictures had come out - or had disappeared into the digital ether. A third visit was a bit more successful.

 

Looking south-east at the northern end of the crag: it is capped by an impressive quiff, not of hair but of sandstone - the 'sandwave'. (Note person on extreme right of the picture for scale).

Here's another view - with climbers in the distance:

Although it resembles a 1950's quiff, it is really the eroded remnants of the last remaining layer of cross-stratified sand, now compressed into stone, that has resisted the Northumbrian weather more successfully than the lower layers.

Looking up at some of the lower layers:

So, an impressive location and an interesting contrast to some of the coastal sites we visited where there are some fantastic fossils and lots of other geologically interesting features. The scenery is good too!

 

[John and Ann Lackie are friends who live on the borders of the Lake District – Ann, under her author’s alter ego of Ann Lingard, has written for this blog in the past. The topic of the ‘sandwave’ arose during a rambling conversation over the course of a delightful pub lunch in the heart of the hills earlier this year. Thanks for this, John - I'll have to make a pilgrimage myself! For more on cross-bedding see this old post.]