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Monday 15 April 2024

The extraordinary Mr Croll -- the world's first glaciologist


James Croll, looking somewhat unhappy.  He didn't like fieldwork very much -- maybe he had just got wet out on the Scottish moors........

James Croll (1821-1890) was an extraordinary man with very little formal education who became a janitor at the museum of the Andersonian University in Glasgow in 1859 and who taught himself (because of his insatiable appetite for learning and his open access to the university library) physics, astronomy and geology.  He corresponded with Charles Lyell and disagreed with him about the origins of what were then called "drift" deposits, but he was greatly encouraged in his researches by Sir Archibald Geikie, and then obtained a position in the office of the Geological Survey of Scotland.

He is revered in Scotland as one of the country's great scientists and as one of the most original of thinkers, and he stood out from the other "glacialists" of the time, who were mostly geologists who happened to be interested ion the Ice Age. I think we should give him the accolade of being the first genuine glaciologist, because of the manner in which he combined the principles of physics, astronomy, climatology and geology in order to understand how glaciers work and how Ice Ages come and go through geological time. 

He saw the Earth as a single system within which events in one sphere (for example, changes in ocean circulation) had repercussions of knock-on effects in all other spheres. He built on the early work of Agassiz in 1840 to argue strongly against Lyell's "great flood" and for extensive landscape modification by expanded land ice. He developed an astronomical theory of oscillatory climate change 60 years before Milankovitch published a very similar theory. He developed a coherent theory of ice sheet growth and shrinkage, and (without any field measurements to work on) developed the idea of an equilibrium profile. He referred quite clearly to feedback mechanisms in glacier behaviour, and wrote about albedo effects. He considered the effects of ice sheet growth and shrinkage on global sea-level, and proposed considerable eustatic drops of sea-level coinciding with glacial maxima during the Ice age. He even started to explore the idea of isostatic loading and unloading, arising from his observations on Scottish raised beaches. He used bore hole records and used field observations on glacial stratigraphy to illustrate his ideas on glacier oscillations and glacial and interglacial episodes. Most extraordinary of all, he created a "model" of the Antarctic Ice Sheet even though, at that time, nobody had set foot on the Antarctic continent, let alone done any measurements on ice thickness, surface gradients and extent. His "model" incorporated innumerable parameters, most of which are still used in computer-based models today. What might he have achieved had there been computers in his day? Then, from his predictions on the nature of the Antarctic Ice Sheet, he had the temerity to use his "model" to suggest what the Great British Ice Sheet might have looked like at the time of maximum glaciation.......... his map was almost a century ahead of its time, and is reminiscent of the maps still in use around 1960, when I was a student.

He was, of course, in 1879  too radical and too far ahead of everybody else to have escaped unscathed -- and towards the end of his life there was a backlash from the more conservative members of the scientific establishment.  In spite of the fact that he was supported and encouraged by the Geikie brothers, and in spite of his copious and creative correspondence with all the great scientists of his day, he never was a full member of the science elite in Britain, and he was known in some quarters as a "controversialist".  The main criticism directed towards him was that his ideas were unsupported by hard evidence and that he strayed too far into the realm of theory  or speculation.  That was all very sad, because one by one his ideas have been accepted and moved into the mainstream -- and field evidence has supported most of his inspired speculations.  Yes, he made mistakes, but that is what happens on the frontiers of science, and the word "extraordinary" is one that will continue to be used for James Croll by those who examine the origins of the science of glaciology.

‘The most remarkable man’: James Croll, Quaternary scientist
Kevin J. Edwards
Jnl of Quaternary Science
First published: 04 April 2022

This is the abstract from Kevin Edwards's paper about this "most remarkable man":


The year 2021 marked the bicentenary of the birth of James Croll (1821–1890), the self-educated son of a crofter-stonemason, whose life was characterised by a dizzying range of occupations and homes, poor health and financial concerns, and yet he became a pioneer of orbital dynamics and ice age climate change with an impressive record of publication. Drawing upon archival information and recently published observations, this paper explores selected aspects of Croll's biography, his scientific connections and controversies, and that area of his life relevant to Quaternary science. He was a 19th century polymath whose multifaceted contributions have been a catalyst for subsequent systems-based climate science on the grand scale, including the foundations for the seminal work of Milutin Milankovitch on the rhythms of Quaternary environmental change.

See also:

Rose J. 2021. Lyell, the Geikies and Croll's observations on terrestrial glacial sediments and landforms. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 112: 261–274.

Sugden DE. 2014. James Croll (1821–1890): ice, ice ages and the Antarctic connection. Antarctic Science 26: 604–613.

Croll, J. 1879. On the thickness of the Antarctic ice, and its relations to that of the glacial epoch. Quarterly Journal of Science, January, 34 pp.

This is James Croll's map (1879), incorporating many components since proved to be correct. Compare with the more modern maps below. Croll was sure that the Scandinavian and British - Irish ice sheets were connected in the North Sea. Flowlines across Northern Scotland were largely correct. The Irish Sea ice stream is shown quite clearly. The ice edge is correctly located on the Celtic Shelf edge. However, Croll assumed that glaciers had a constant surface gradient from centre to periphery; the glacial equilibrium profile had not yet been discovered. So he greatly overestimated ice thickness in the centre of the accumulation area. Consequently, his image showing thick glacier ice flowing across southern England was somewhat overenthusiastic!! He has ice flowing down the Bristol Channel from east to west -- precisely the opposite of the ice flow pattern as understood today.

The most recent ice flow maps, mostly computer generated, are more correct that Croll's map -- but they are still faulty in some areas because of modelling mistakes and inadequate ground truthing.


Also found on the web:
Achievements and Key Points

James Croll:

Was the foremost advocate in the 1800s of the idea that climate change is caused by the changing relationship between the earth and the sun.
Devised they theory that climate is controlled by solar insolation – the amount of energy reaching the earth from the sun.
Linked our planet’s ice ages to solar insolation variations caused by: Earth’s elliptical orbit around the sun (100,000-year cycle); precession of the equinoxes (23,000-year cycle); and axial tilt (41,000-year cycle).
Noted how the elliptical shape of Earth’s orbit around the sun varies with time – sometimes the ellipse is more eccentric (elongated).
Said ice ages happen when there is a combination of events: the earth’s elliptical orbit around the sun is at its most eccentric and mid-winter takes place when the earth’s orbit is at its farthest point from the sun. These conditions of reduced sunlight result in lower temperatures, leading to a build-up of ice and snow in the oceans and on the ground.
Said the build-up of ice redirects the trade winds and hence ocean currents. Warm currents like the Gulf Stream no longer bring heat from the tropics to the colder regions, enhancing the orbital cooling effect, leading to ice ages.
Advanced the theory of ice-albedo feedback. This says that if ice begins accumulating at a pole because of a decrease in winter sunlight, then the extra ice will reflect more of the sun’s heat back into space, leading to further cooling.
He (incorrectly) said ice ages alternate between the northern and southern hemispheres – the north and south taking it in turns to have moderate climates and ice climates in a cycle lasting 22,000 years in each hemisphere, with each ice age lasting about 10,000 years.
Although today we know Croll did not get all the details correct, his work provided a mechanism that explained the ice ages. It provided a basis for Milutin Milanković to go further the following century and generate the concept of Milankovitch cycles.


This is an interesting programme from 2010, in which Iain Stewart talks at some length about the life and times of James Croll -- starting about 30 mins into the programme.


Tony Hinchliffe said...

Hats off to James Croll! Immediately on reading the first part of your piece, Brian, my thoughts turned to John Evans a colleague of Stonehenge archaeologist and academic at Cardiff University, Richard Atkinson. Here is what Mike PP has to say about John Evans.

"I'd known Evans in his later years when he was professor of environmental archaeology. He became the leading specialist in land molluscs 'snail Evans' to distinguish him from lots of other archaeological Evanses - and one of those people who's interested in everything......These days mavericks like John don't get jobs in universities - or if they do they don't last long..... [ MPP: Stonehenge, 2012, page 239]

BRIAN JOHN said...

I remember John -- he and I were almost contemporaries. Met him occasionally on field trips and QRA meetings. If I remember rightly, he used to hire a cottage near Aberbach, right next door to Abermawr. We visited him there once, and we spent some time looking at the Pleistocene sequence at Abermawr. As I recall, we agreed on pretty well everything.......

BRIAN JOHN said...
This comment has been removed by the author.
Tony Hinchliffe said...

Well, well, what a small world it is. I'm not sure whether Mike Allen, an environmental archaeologist who runs his own business not that far from me, just south of Warminster and within an hour's walk of CLAYPIT HILL ( discussed recently on the Blog) knew or worked with John Evans. UPDATE, he may well have, he certainly was aware of him, see the end of my Comment. Mike Parker Pearson said Evans was known as 'snail Evans'. Mike Allen's house (which I've walked past} is called Escargot!......he may be mildly obsessed with'em. Allen has of course worked a great deal with MPP, particularly on the Stonehenge Riverside Project, rather than the efforts in the Preseli hills. I WISH we could recruit him to do his environmental science work on Salisbury Plain vis a vis the geology, notably the clay - with - flints such as at Claypit Hill. He's done a lot in the Wylye Valley the book: "Land and Memory: papers in memory of John G Evans", 2009.

BRIAN JOHN said...

I recall that Mike Allen was quite heavily involved when MPP declared that the solution rills at Stonehenge were highly significant "periglacial stripes" -- garnering international headlines about Stonehenge's location finally being revealed by exciting new research etc etc etc....... I have no idea what Mike REALLY thought about all of that......

Tony Hinchliffe said...

Nor have I! He seems a very organised bloke in his own projects. I'd love to know what he'd like to do, given the finances, at various prehistoric sites. He recently investigated the Cerne Abbas Giant on behalf of the National Trust, described as "secrets and surprises" in British Archaeology, May - June 2024.

Tony Hinchliffe said...

By a complete coincidence, my wife and I turned up at Stonehenge one day on a rare whim. Mike Parker Pearson informally addressed some of us members of the visiting public. Having actually used the word "geomorphology" as he explained his belief in the existence of interglacial stripes close to the monument, he announced that he had to now go over yonder to address the Japanese television crew. Very persuasive approach. No shrinking violet.