Ice Age Beginnings
How was the British landscape created?
This subject is studied in great detail by people in academic institutions, and is , in technical terms, well recorded.
If you are one of the acknowledged experts in these institutions, or even an unacknowledged expert, you probably won't believe a word of this discussion. However, the research is the fruit of several years of original scientific evaluation of data that owes nothing to historic hypotheses of ice age events. I urge you to read my fumbling explanation with an open mind, please!
Publications that interpret scientific data and define the recent period in which the major geographic features of Britain were formed are written by some of the leading scholars in their fields.
Some of their extensive and detailed reports, with their interpretations, are listed below, for reference:-
"Tunnel valley formation beneath deglaciating mid-latitude ice sheets: Observations and modelling" by James by D. Kirkham et al
"The northern sector of the last British Ice Sheet: Maximum extent and demise" by Tom Bradwell et al
"Glaciology of the British Isles Ice Sheet during the last glacial cycle: form, flow, streams and lobes" by Geoffrey Boulton et al
"Growth and retreat of the last British–Irish Ice Sheet, 31 000 to 15 000 years ago: the BRITICE-CHRONO reconstruction" CHRIS D. CLARK et al
"Glacial processes and landforms" by David J. A. Evans et al
"Retreat dynamics of the eastern sector of the British–Irish Ice Sheet during the last glaciation" by DAVID J. A. EVANS
"A chronology for North Sea Lobe advance and recession on the Lincolnshire and Norfolk coasts during MIS 2 and 6" by David J.A. Evans
"Subglacial bed conditions during Late Pleistocene glaciations and their impact on ice dynamics in the southern North Sea" by SANDRA PASSCHIER et al
"Provenance and depositional environments of Quaternary sediments from the western North Sea Basin" by Davies, B.J. et al
"Pattern, style and timing of British–Irish Ice Sheet advance and retreat over the last 45 000 years: evidence from NW Scotland and the adjacent continental shelf" By TOM BRADWELL et al
"Streamlined hard beds formed by palaeo-ice streams: A review" by Maarten Krabbendam et al
I cannot compete with the excellence of these people's work, but I do offer an alternative view.
This view recognises that each of the classic ice ages on Britain occurred in three phases, leaving clear evidence of each of these phases on our landscape.
Phase one, in any ice age event, happened when year on year snowfall built significant thicknesses of snow which "stuck" on drained land. Multiple years of precipitation accumulated hundreds of metres thicknesses of packed snow which remained as a static sheet across the landscape.
The evidence of this is demonstrated in the record of sealevel change compiled by Ian Shennan, where the millions of tons of ice that accumulated in the last ice age compressed Scotland and northern England into the earth’s mantle.
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The brown dots on Ian Shennan's plan of Britain and Ireland indicate where the thickness of glacial ice was thickest. The black dots indicate where ice was thinnest, or absent. While it is obvious where the thicker ice was, the evidence for snow elsewhere is more nuanced, and the main purpose of this research is to establish the changing presence of snow within the period of the last ice age.
The ice sheet that formed during a cold period would have been static. Movement of this material required an inclined terrain, and a space into which any sliding ice would slide to occupy.
Any ice sheet in such a position, able to slide down a slope, would do so when it was still thin, at 5 metres, or ten metres, and not wait until it had developed a depth of hundreds of metres.
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The second phase within any glacial period, saw the deglaciation of the ice sheet. This happened at different rates, depending on the prevailing global temperature. More often than not though, the thaw was fast, causing the edge of the ice sheet, to melt quickly, and to collapse vertically onto the land that had supported it. The falling ice cracked the underlying bedrock, and created valleys. Most of the valleys, rivers , and ribbon lakes of Britain are attributable to this phase.
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The third and final phase of this process occurred when the huge piles of ice created by the collapsing ice sheet flowed away from the ice sheet edge. This would have been a river of meltwater sludge loaded with ice blocks and broken rocks. As it flowed downhill the rocks caught up in the mix would have scratched the rock formations that the fluid crossed, and when the whole mess reached water, the ice would have melted out , leaving moraines and "groundling zone wedges".
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The most recognisable features of the European landscape, hills and valleys, were developed over the last 150,000 years, but were overprinted onto features from half a million years ago, or more.
That half million year span is illustrated in the graph below, showing long periods of extreme cold weather, in which ice sheets were accumulated over northern Europe, specifically on Norway, the European Alps, and Britain/Ireland.
To some extent the ice sheet over Britain and Ireland differed to those elsewhere on the continent, in that the archipelago was very close to warm water, and stormy seas, which had been ( and still is!) funnelled up the Atlantic ocean from warm equatorial waters. Warm water carrying violent storms had a major influence on how the British and Irish Ice Sheet developed.
The chart above shows our current understanding of the history of temperature variations on the planet over the last half million years.
In that time there have been basically four cold periods, with the most recent of them "our" last ice age lasting from 120,000BP to 12,000BP.
A feature of all the ice ages shown seems to be that they tended to start quite slowly, getting colder quite gradually, but when the cold periods ended, their rise in temperatures and melting, was quite dramatically fast.
And so it was with "our" ice age.
(Note on images generated by me. These indicate suggested locations for the edges of formations and other features. They are not accurate, and may in future be regarded as misleading. At present they are a best guess to give other researchers something get their teeth into!")
The first episode in the series, that led to our own times was between 150.000BP and 140,000BP, when the ice age that preceded our last ice age ended. Temperatures rose quickly and ice sheets melted. The ice sheets collapsed on Scotland, Northern Ireland, and the European Alps. Their collapse caused impact valleys to be cut and recut across the landscape, dumping huge volumes of glacially produced sedimentation to be laid in the North Sea, as the Ferder Formation, and the Coal Pit Formation.
The second episode between 140,000BP and 120,000BP (above) saw a long period of high temperatures, possibly higher than our own. This period was long enough that the Ferder Formation was cropped, and possibly the Coal Pit Formation, also. (Gatliff and Johnson)
The third episode from 120,000BP to 70,000BP was a cold period causing ice sheets to accumulate in the northern hemisphere. At this time , as ice sheets built, sea level fell, and the location of the British ice sheet was limited approximately to the outline of the British archipelago.
The fourth episode between 70,000BP and 60,000BP saw a fast rise in temperatures, in which the ice sheets contracted to the mountains of the archipelago, in England, Scotland, Wales and Ireland. At this time deep glacial deposits were laid onto the cropped surfaces of previous marine events.
Around Shetland was the Capeshore Formation; east of Scotland were the Swatchway Formation and the Marr Bank Formation; while south and along the English coast were the Wee Bankie Formation and the Bolders Bank Formation which merged with the Dogger Bank, and followed around it's southern coast.
The fifth episode between 60,000BP and 40,000BP was a short warm period , peaking at 43,000BP. In this time-frame ice sheets were maintained on mountains. Lowlands were the territories of cold adapted creatures and plants through this time, and the coastal, offshore areas may have been Lagoons, as there is evidence that a ridge of land separated them from the Norwegian Channel, against the Norwegian Coast.
The sixth episode between 40,000BP and 21,000BP, saw temperatures which blanketed the northern hemisphere with ice again. This time the ice sheet extended out from the mountains of Britain, across to the Norwegian Channel, and south to the English Channel.
The ice sheet left a lagoon unfrozen off the east coast of Britain.
The final period is the seventh episode, after 21,000BP, which saw temperatures rise to today's levels. At this time most ice sheets on northern Europe melted away completely. The retreat of the ice sheet edge was fast in around 21,000BP, cutting the Dover Strait. It was then slow until 18,000BP when a short few years of retreat left the deep palaeovalleys of the Witch Ground in the North Sea. The retreat then slowed from 18,000BP, until 15,000BP, when much of the coastal regions of northern Britain were cut.
Finally before 11,000BP the last major hilltop ice sheets were collapsed, sending huge streams of broken ice and stone in a meltwater sludge, across the British landscape, out and into coastal waters where the ice melted out leaving moraine-like deposits.
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"Parallel Valley Arrays" is the first of a series of blogs defining the impact valley, a major landscape feature of the British landscape.
"Ice Age Beginnings" describes the context for the events that created the British landscape.
"Archaeology of the North Sea " describes evidence in the written scientific literature which suggests a local context in the North sea that would have allowed a rodent (the Orkney Vole), and other creatures to travel from Europe to Orkney without setting foot on British soil.
"Walkable Land in the North Sea" charts the probable existence of a land bridge from Holland to Norfolk which allowed flora, fauna, and people, to commute between Europe and Britain in the early Neolithic era
Having provided some reasoning that would suggest that Neolithic people walked from Europe to Britain, it is more difficult to sustain the idea that they used boats to sail from Scotland to Orkney "Neolithic Migration to Orkney" leads into a myriad of articles that describe what happened in early Neolithic Orkney, and again what happened when people could no longer walk from Caithness to South Ronaldsay.
All opinions my own.
Jeffery Nicholls
South Ronaldsay
Orkney
Jiffynorm@yahoo.co.uk
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