New book on geology and landscape of the Britsh Lake District

I don’t often review books on Earth-logs, but one that is pending publication may interest readers (Ian Francis, Stuart Holmes and Bruce Yardley 2022. The Lake District: Landscape and Geology. Marlborough: The Crowbrook Press; ISBN: 078 0 7198 4011 1). Ian Francis urged me to create Earth Pages, the predecessor to Earth-logs. One good turn deserves another, but this is a very good book. Unlike nearly all area-specific geoscientific books it is not primarily a guidebook. Instead it uses the internationally famous Lake District as a means of teaching how to fathom what a landscape represents. In this case, one with a history going back half a billion years, involving closure of an ocean, destruction of a mountain chain and sediment deposition in a ‘shallow, inland sea’. The last couple of million years or so of cycles of glaciation and river erosion have sculpted its present form. Finally, it became the home range of human hunter gatherers, once the ice had melted away around 10 thousand years ago. Britain’s first stone-age tillers and herders colonised its lower elevations, followed by miners and metal smelters, Roman, Viking and Anglo Saxon invaders and settlers. Its beauty and complexity have inspired poets and artists, and they in turn have drawn in more visitors per km2 than perhaps any other National Park on Earth, and far more per annum than its indigenous population.

Cover of The Lake District: Landscape and Geology

Ian, Stuart and Bruce lace their book with some of the best landscape images of the Lake District that I have come across, which invite you to read the text. The Lake District is pitched at a level that anyone can understand, with a minimum of jargon and a pleasant style. Basic geological concepts are covered in separate ‘boxes’, where the main thread requires them and for those who want a little more science. Geology being an observational science, there is some emphasis on indicators of natural processes, such as elliptical drumlins whose sculpting by flowing ice aligns their long axes, and exotic boulders made of rocks only present miles away whose presence suggests the source of the ice that had moved them. Solid rock outcrops in the Lakes are products of many Earth processes, both internal and at the former surface. There are granitic rocks that intruded through once volcanic and sedimentary rocks. Their internal features tell the rocktypes apart, such as the layering of sediments, often cleaved and folded by deformation. and the lack of structure in granite that cuts the layering, yet imparts new minerals to the older marine rocks as a result of igneous heating to very high temperatures.

Most of the geological concepts raised in the main text are amplified by narratives of seven field trips; provided the reader physically walks through them. And why shouldn’t they? Each of them involves only a few kilometres of gentle walking from parking spaces on metalled roads.  They cover all the solid geology, from the regionally oldest rocks, the Early-Ordovician, deep-water Skiddaw Slates; upwards in geological time through the varied products of later Ordovician volcanism and marine sediments; the thick Silurian mudstones and silts; and the youngest and structurally simplest shallow-marine Carboniferous limestone. The sediments all contain fossils and the volcanics are full of evidence of the environment onto which they poured – an oceanic island arc. A simple story is unveiled by all, such as following a track on the flanks of Blencathra, a hill in the Northern Fells. From slates with cleavage formed by compressive forces acting on muds; to a point where new minerals have grown in them through later heating; then to where heat was so intense that the slates came to resemble igneous rocks; and finally outcrops of a granite whose much later intrusion as magma explains the simple sequence. All the trips are like that: not too much to take in, but enough to hammer home the various rudiments of geology.

Britain was where the modern Earth sciences were largely forged. But that was in the absence of complete exposure of all the solid rock that underpins it. What lies between outcrops is the modern natural world and a diversity of ecosystems to which The Lake District also draws attention. Even professional geologists get bored to tears by trudging unendingly over nothing but rock. They enjoy flowers, trees, birds, streams and tarns with fish as a relief. Some of the text also taught me about oddities created by Cumbrian farmers: bields, which are shelters for shepherds and sheep; washfolds where sheep used to be gathered and cleaned prior to shearing, and lots more about the unique upland farming culture of Cumbria. I hope the book proves physically durable, for it will surely find its way into secondary-school and first-year undergraduate field trips. It is also ideal for any family aiming at a fortnight’s holiday in the Lakes, but wondering what to do. The book will get well-thumbed and wet – the one drawback of the Lake District is its annual rainfall, averaging 3.3 metres! Go in April, May or early June to escape the worst of it and that of tourists, and to see its ecology at its best. I’m giving my complimentary copy to my grandchildren, because I get annoyed when they complain of boredom!

New Feature: Picture of the month

Having belatedly discovered The Earth Science Picture of the Day website (it has been going since September 2000; as long as Earth Pages!) I thought readers of EPN might like the aesthetic boost that it provides. So, on the last day of the month I intend to insert a link to what I think is the best of those contributed to EPOD over the previous 4 weeks or so.

The Great Unconformity of the Grand Canyon (credit: Stan Celestian
The Great Unconformity of the Grand Canyon (credit: Stan Celestian)

EPOD has a vast archive of contributions and each one has a brief description and links to other visual resources.

The Time Lords of Geology

Epic Time Lord
Time Lord, possibly outside the offices of the International Commission on Stratigraphy (credit: Sorcyress via Flickr)

Because it is the ultimate historical discipline, the essence of geology centres on time, measuring its passage and establishing correlations in time on a global scale so that an interlinked story of Earth evolution can be told. In fact geology is not just about a record of what happened in the four dimensions of place and time; it is a great deal more multidimensional, involving temperature, strain, chemistry, erosion, deposition, sea-level , the course of life and much more besides. Ever more multifaceted and, sadly, divided into subdisciplines and interfaces with other aspects of natural science that few if any individuals can grasp, an almost legally enforceable set of rules is needed to keep the order orderly. Unlike history and more akin to archaeology geological time is of two kinds, its precisely quantitative measure being a relative newcomer.

Since it emerged in the Enlightenment that began in the late 17th century geology has been dominated by a relative sense of timing: Steno’s Law of Superposition, and those relating to deformation, igneous eructations, erosion and deposition, first addressed systematically by James Hutton, being the most familiar. The notion of an absolute time scale into which events separated relative to one another could be fitted with confidence is a real latecomer. Although first attempted between 1650 and 1654 by Archbishop of Armagh James Ussher – he reckoned from the  Old Testament that everything began at dusk on Saturday 22 October 4004 BCE – the only useful and broadly believable approach to absolute time has been based on the decay of radioactive isotopes incorporated into minerals once they had formed within a rock. But that is no panacea for the simple reason that most of them form through igneous or metamorphic processes and only rarely in the course of sedimentation. It also has only become reliable and precise in the last two or three decades.

Tying together global records of all the kinds of process that have made, shaped and changed the Earth has therefore become an increasingly complex blend between local relative dating, burgeoning regional to global means of correlation and the odd point in absolute time. What has arisen is a dual system that, if truth were told, is often used in a cavalier fashion. Equally to the point, the rules have of late become unfit for purpose and are in need of revision, which is a task for the Time Lords, properly known as the International Commission on Stratigraphy (ICS). The trouble is, the rules have themselves evolved somewhat episodically while their subject is appropriately in continual motion and change, if not anarchic. To the outsider things can seem very odd indeed. Most reasonably well-read souls will have heard of the Cambrian and the Jurassic, largely because of the popularity of trilobites that blossomed in the one and dinosaurs that strutted the land in the other. What is less well known is that the two names have different usages as adjectives: one to signify an interval of time called a Period, the other a System of essentially piled-up sedimentary rocks.

There are greater dualisms that group the Period/System divisions: the largest Eon/Eonothem groupings of Archaean, Proterozoic and Phanerozoic; the Era/Erathem signifiers such as Palaeoproterozoic, Mesozoic and Cenozoic. Incidentally, the time between the formation of the Earth and the first palpable rocks, from about 4550 to 4000 Ma, has been called the Hadean but has no designated status, possibly because it has no rock record whatsoever. Divisions of Periods/Systems apply only to the time since fossils became abundant 541 Ma ago, and in order of fineness of division are Epoch/Series and Age/Stage. Example of the first can be Lower, Middle and Upper – to spice things up, Middle maybe omitted from some Periods/Systems – or they might be given names derived from type areas, such as the ever popular Llandovery at the base of the Silurian Period/System. Helpfully, the Cambrian contains Terreneuvian, Series 2, Series 3 and Furongian from early to late/bottom to top. The final global division has always floored undergraduates and shows little sign of relief – there are a great many Ages/Stages, in fact a round 100 (I may have miscounted), 98 with names, 2 currently unnamed and 4 in the Cambrian called Stages 2 to 5: confusing, that… has anyone spoken of the Stage 3 Stage or the Stage 5 Age of the Cambrian?

Worryingly, in my hasty overview of the ICS International Stratigraphic Chart above I have reversed the official designation of chronstratigraphic/geochronological nomenclature: is this likely to have me committed to the geoscientific equivalent of Guantanamo Bay, or merely limbo?

I have by no means exhausted officialise. Readers may not be surprised to learn that the Time Lords have bent Heaven and Earth literally to concretise the double entendres of geology. The base of almost every Age/Stage in the Phanerozoic Eonothem/Eon is defined at a suitably agreed point on the ground by, in a few cases, a real golden spike (I may be mistaken on this, as the only one I tried to visit was at the base of a Welsh cliff suitable only to be visited by – in the timeless phrase – ‘a strong party’). More prosaically there are monuments of various ethically appealing designs that go by the sonorous name Global Boundary Stratotype Section and Point. I have it on reasonably good authority that ICS delegates have, on occasion, needed to be physically restrained from fist fights over which nation shall host a particular GSSP (the ‘B’ in the acronym is aspirated).

This is the point that all readers will have been waiting for: it has been suggested to ICS that the whole edifice is looked at very closely and perhaps revised (Zalasiewicz, J, et al. 2013. Chronostratigraphy and geochronology: A proposed realignment. GSA Today, v. 23 (March 2013), p. 4-8). For professionals this is an obligatory read, for others optional: there is no excuse as it is downloadable for free – click on the title. While you are about it, you can also download from GSA Today the famous proposal for an entirely new series/epoch called the Anthropocene (see also A sign of the times: the ‘Anthropocene’ in EPN issue of May 2011)

Time wars flare up again

English: A diagram of the geological time scal...
Time's spiral Image via Wikipedia

Last year Earth Pages News reported a rationalisation of the way in which geological time is signified (Rationalising geological time 7 May 2011). A working group set up by the International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Geological Sciences (IUGS) defined the year as the base unit, standardizing it to the time in seconds between one solstice and the next at the equator for year 2000 (3.1556925445 × 107 s) thereby linking it to the Système international d’unités or SI base unit of the second, itself defined in terms of behaviour of the caesium atom. It is to be signified by ‘a’ for annus (year in Latin) and preceded by ‘k’, ‘M’ and ‘G’  for thousands, millions and billion years, complying with the SI progression in steps of 103 for units.

The sticking point for some, mainly in the US (e.g. Science magazine and many geoscientists there) is that the ka, Ma, Ga symbols are to apply not only to times before the present but also to spans of geological time. Since the agreed convention is incorporated into SI it has almost the force of law for scientists , so that the Cretaceous Period will be said to have begun at 145.5±4.0 Ma ago, ended at 65.5±0.3 Ma ago and was 80 Ma long, instead of the latter being in m.y., m.yr., mya  or Myr according to what seem to have been personal quirks or those of scientific journals.

Somewhat florid reaction against the rationalisation (Christie-Blick, N. 2012 Geological time conventions and symbols. GSA Today, v. 22 (February 2012 issue), p. 28) seems to have flowed from a deliberation on the IUPAC-IUGS proposal (in Prague, Spring 2010) by a lesser world body: the International Commission on Stratigraphy’s  (ICS) International Subcommission on Stratigraphic Classification (ISSC). The meeting voted 16 to 2 to reject the proposal – a substantial number of voting members abstained – claiming that it violated SI ‘rules’ regarding base- and derived units. The issue, on reaching the ICS meeting, as the same Prague workshop, seems to have been greeted by a 50:50 split. A closed meeting of the ICS Bureau (now we can begin to see the kind of thinking involved here…) on the workshop’s last day unanimously adopted the motion ‘We neither accept nor reject the IUGS-IUPAC Task Group’s recommendation to apply Ma, generally, as the unit of deep time. We accept the argument for Ma as a single unit for time but would recommend flexibility, allowing for the retention of Ma as specific notation for points in time (i.e., dates) and myr as a unit of time denoting duration. We agree with the spirit of this statement’ [my italics]. ‘Neither accepting nor rejecting’ is something familiar from minutes of the Central Committee of the former USSR, being rumoured to have been Joseph Vissarionovich Stalin’s favoured formulation in moments of uncertainty: a little like the old ‘Belfast Question’, ‘Are you for us or against us’ from someone whose politics is not entirely clear.

An argument proffered by Christie-Blick is, ‘No one objects to the storming of the Bastille on 14 July 1789 (a date) or to the construction of Stonehenge from 2600–1600 BC (an interval specified by two dates). In the case of the latter, we say that the job took 1000 years, not 1000 BC.’ This forgets something quite practical: geochronologist rarely if ever, ‘neither accept nor reject’ AD, BC BCE, or CE but express time in years before present, with the odd convention that ‘the present’ was 1950, before atmospheric testing of thermonuclear devices. What is wrong with the answer to the question, ‘When did the Cretaceous begin?’ being 145.5 Ma ago, or ‘80 Ma’ in answer to, ‘How long did it last?’ Who would prefer the alternative to the second question –  80 (choose your preferred symbol from the following: m.y., m.yr., mya.  Myr., million years or millions of years)?