Monday, 28 August 2017

Week 47: (21st August to 27th August 2017) or 'Punctures in Somerset'

Muddy boots. Shropshire sands and Herefordshire clays, which had stowed away in the soles since woodland fieldwork, became married with Somerset soils. This week, I planned to extract cores down a field in Shepton Beauchamp; cores which would stretch down 4m underground, to bedrock. The principles remained the same - the need for saprolite (weathered bedrock) and overlying soil samples - but there the similarities grew distant. The farmland posed many interesting and novel challenges, one of which being the deeper soils at the base after decades of soil deposition, two deep alas to manually dig a soil pit. The issue, fortunately, was relieved. A lorry reversed into the farmland forecourt; strapped within it was a solution.

The mouth of the lorry yawned and the animal awoke. Emerging over the lip, a large metal dinosaur roamed steadily towards the ground. It's neck, locked in contortion along its own back, was set free and it elongated out, doubling its height to survey the area. Minutes of adjustment passed; a menacing sustained groan rumbled from within. It had neither legs nor arms, but a belt underneath its belly, conveying itself sluggishly over the furrows. And then, when it assumed its rightful position over one of my proposed coring sites, it dipped its neck, picked up a long tubular corer and prepared to beat it into the ground. First, silence. Then... Bang! In an abrupt execution, it recoiled its head and sent it with merciless fury back down to beat the corer, puncturing the soil. Then, again, and again... fifty, perhaps one hundred times, each seemingly as violent as the previous.

The acupuncture became more arduous; the metal corer now 2m deep underground began to argue against the prolonged beating, resisting further incision. It's demands were ignored and the beating continued. Bang! And then, silence was draped over the area once more. The corer was clawed out of the ground and with it an in-tact core of soil.

What I have just described, albeit perhaps with animalistic qualities, is the Dando Drilling Rig, operated by the drilling team at the BGS, and often employed in borehole projects. Despite the name, its more of a large, mechanical hammer than a drill, and with the correct use of multiple extension rods, it can stretch down to over 10m. My ambitions to puncture only 4m of Somerset, I imagine, did not exhibit its full potential but what I saw justified its usage. In 6 hours, a total of 10m of Earth were entombed within plastic. Soon after, they were kidnapped.

The rocks that lay at the depths of my core have not seen daylight since dinosaurs roamed the Earth, over 180 million years ago. The Bridport Sandstone that underlies much of my study field was formed when sediment settled at the bottom of warm, shallow seas that once inundated the area. 180 million years later, the sandstone lays underneath a duvet of silty, loamy soil. Once, the region may have been swarming with giant, plant-eating dinosaurs. Today, it grows potatoes and maize to be sold in supermarkets and bought by hungry humans. With the Dando Drilling Rig, the sandstone, asleep in the dark for 180 million years, was awoken in a matter of minutes.

The Bridport Sandstone has travelled thousands of miles. It was laid down when the UK was enveloped within one large super-continent. Where precisely it was formed from, I nor anyone can state for sure, but I can confirm, with extraordinary accuracy, that its final hundred miles were spent aboard a lorry, cruising with satisfying ease up the M5 to Birmingham, where they encountered the first 'delays' in their 180 million year history. Their final hundred miles in jams were hellish, but I imagine even the punctuated journey up the M69 and M1 was relatively speedy compared to the tortuously slow migration they've been subjected to these last hundred million years.

In a rather vacuous, dusty basement at the BGS, the teeth of a saw bite through the cores. They are sawn length ways, revealing the profile in preparation for sub-sampling. Then the knife is wielded, and as if one is segmenting a fig roll, the cores are partitioned into 5 cm increments and bagged. Although the samples are yet to be analysed, the knife is an informative tool. The pressure required to slice through the core suggests its density, whilst the ability for the sliced piece to sustain its shape following the cut is testament to its soil structure. What's interesting is that there are bands where the core, overwhelmed by the knife, reduces to a mound of crumbs. In catering, this missing ingredient would be a binding agent. In Soil Science, it's clay. But further tests will no doubt reveal all.

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