Membership is completely free, giving members unlimited access to all available resources, services, features, and benefits without any restrictions or fees.
Welcome back. Sign in to continue enjoying unlimited access to all available resources, services, features, and member benefits at no cost.
This was not yet the Last Glacial Maximum, the later phase when the British–Irish Ice Sheet reached its greatest extent. Current reconstructions place the maximum expansion of ice around Ireland and its continental shelf broadly between about 27,000 and 23,000 calibrated years before present, although the timing differed between sectors. Around the notional date considered here, ice was growing on a continental scale, sea level was falling, and Ireland’s geography was changing rapidly. Low sea level exposed areas that are now seabed, while glaciers, meltwater and permafrost altered routes across the wider Irish–British region. That did not necessarily make travel simple: exposed ground could be cold, boggy, cut by rivers, or blocked by ice and unstable margins.
This was not yet the Last Glacial Maximum, the later phase in which the British–Irish Ice Sheet expanded to cover Ireland and much of the surrounding continental shelf. Yet neither was the island simply free of ice. Research increasingly indicates that the British–Irish Ice Sheet had a long and dynamic history, with growth, retreat and renewed advances before its maximum extent. The precise position of ice margins around 33.8 thousand cal BP remains uncertain, and may have differed sharply from one region to another. It is unsafe to imagine a single uniform map for the entire island.
MIS 3 broadly covers the interval before the most extensive phase of the last British–Irish Ice Sheet. It was not a single, unchanging “Ice Age”. Greenland ice-core records and Irish cave mineral deposits both indicate abrupt alternations between colder stadials and relatively milder interstadials. At Crag Cave in County Kerry, uranium-thorium dates show that stalagmites formed episodically during the last glacial period. Because liquid water was needed for their growth, these phases provide strong evidence that south-west Ireland sometimes experienced conditions above freezing, although they do not by themselves reveal the precise appearance of the landscape outside the cave at 31,831 BCE.
The label 31,836 BCE gives a useful position on a modern timeline, but it cannot identify an event in Ireland during a particular year, season or generation. There are no written records, settlements, graves or securely dated occupation surfaces from which such precision could be claimed. In conventional “before present” notation, where present means 1950, the calendar arithmetic places this notional year at about 33,785 years BP. That is not itself a laboratory age. Radiocarbon measurements carry statistical uncertainty and must be calibrated against changing atmospheric carbon-14 levels; at this depth of time, their calendar ranges can span centuries or millennia.
This was the later part of Marine Isotope Stage 3, a long and climatically unstable interval of the Late Pleistocene. Ireland was approaching, but had not yet reached, the fullest expansion of the last British–Irish Ice Sheet. Modern reconstructions show that ice growth and retreat were uneven between regions rather than one simple island-wide advance. The principal maximum came later, broadly between about 27,000 and 23,000 calibrated years before present, although individual sectors behaved differently. Around the notional year in question, ground in some areas was still available to plants and animals, while glaciers and ice masses were expanding elsewhere.
Ireland was approaching, but had not yet reached, the maximum expansion of the last British–Irish Ice Sheet. That later maximum is now generally placed around 26,000 calendar years ago, with the greatest ice volume following several millennia later. Around the notional year considered here, cold conditions certainly prevailed, but neither temperature nor ice cover was uniform across the island. MIS 3 was punctuated by abrupt shifts between relatively milder interstadials and severe stadials. The island’s terrain was consequently altered by frost, seasonal thaw, wind, snow and moving water as well as by the fluctuating margins of ice.
Radiocarbon dates are not calendar dates. A laboratory measurement records the remaining radioactive carbon in a sample and is conventionally expressed in radiocarbon years BP; it must then be calibrated against independently dated records of changing atmospheric carbon. At the depths of time involved here, calibration can produce broad and sometimes discontinuous probability ranges. A date such as 31,874 BCE is consequently useful only as a modern reference marker: it cannot identify a season, a generation, or even a discrete archaeological horizon. The relevant evidence comes instead from deposits whose ranges overlap that point in time.
Radiocarbon dating does not translate automatically into a calendar year. A laboratory measures remaining carbon-14 in organic material and produces an age in radiocarbon years before present, where “present” conventionally means 1950. That result must then be calibrated against records of past atmospheric carbon-14. At this antiquity calibration produces ranges, sometimes broad or irregular ones, rather than an annual date. The internationally used IntCal20 curve extends to 55,000 calibrated years before present, but its older section necessarily combines several kinds of environmental archive and retains uncertainty.
“31,900 BCE” is a useful modern label, not a year that can be recovered from Ireland’s prehistoric record. No Irish calendar, written account, ruler, settlement sequence or human life can be assigned to that precise point. In radiocarbon and ice-sheet research, dates are normally expressed as ranges of calibrated years before present (cal BP, where “present” is AD 1950), often with sizeable uncertainty. In that convention, 31,900 BCE is roughly 33,850 years before present. It falls within Marine Isotope Stage 3 (MIS 3), a long and climatically unstable part of the last glacial cycle, and just before the great expansion of the British–Irish Ice Sheet that culminated several millennia later.
This notional year falls in the Late Pleistocene, within Marine Isotope Stage 3: a cold, climatically unstable phase of the last Ice Age. It preceded the fullest expansion of the last British–Irish Ice Sheet. Current syntheses place the period when ice entirely covered Ireland and extended towards the Atlantic and Celtic Sea shelf edges broadly around 27,000–23,000 calibrated years before present, although the growth and maximum extent of different sectors were not simultaneous. The island at 31,931 BCE was therefore approaching, rather than securely within, that later maximum.
The numbered year should not suggest false exactness. In archaeological convention, “before present” is measured from 1950, while BCE is a retrospective calendar system. A conversion from 31,932 BCE gives only an approximate position of about 33,900 years before present; it does not identify a single excavated deposit or a particular season. Radiocarbon ages are not calendar ages, and their calibration depends on a curve built from several natural archives, including tree rings, corals, lake sediments and cave deposits. At this antiquity, calibrated results can be broad and sometimes discontinuous.
Ireland was not simply a timeless white wilderness throughout the whole Ice Age. The climatic sequence was uneven, and the growth of the final great ice sheet was a process, not an instantaneous conquest of the island. Evidence from organic deposits sealed beneath till at Derryvree and Greenagho in County Fermanagh indicates that north-central Ireland had been ice-free until at least about 34,000 years ago. A synthesis of the evidence consequently places the principal build-up and expansion of the last Irish Ice Sheet between about 34,000 and 24,000 years ago. The numbered year in this article sits at or very close to the beginning of that long transition.
Ireland then stood on the threshold of the last great expansion of the British–Irish Ice Sheet. It was not yet simply the ice-covered island of popular imagination. Geological evidence from beneath later glacial deposits at Derryvree and Greenagho in County Fermanagh indicates ice-free conditions in north-central Ireland until at least about 34,000 years ago. The calibrated ranges are broad: organic material at Derryvree falls within c. 36,900–31,700 cal BP, while material at Greenagho falls within c. 37,200–35,700 cal BP. They establish an environmental sequence, not the weather or shoreline of a particular year.
The date 31,957 BCE is close to, but should not be equated exactly with, claims concerning a reindeer bone from Castlepook Cave near Doneraile in north County Cork. County Cork heritage publications describe the fragment of reindeer femur as c. 31,000 BCE and identify a deep mark interpreted by zooarchaeologist Ruth Carden as having been made by a sharp stone tool during butchery. The wider Castlepook fauna includes animals whose radiocarbon determinations belong to the middle and later parts of the Late Pleistocene. Yet the precision implied by a single numbered year is illusory: radiocarbon results have errors, must be calibrated, and dates from older excavated collections require particular care.
At around this point in the deep past, Ireland lay at the north-western edge of the European world inhabited by Upper Palaeolithic hunter-gatherers. It was not yet the fully ice-covered landscape associated with the peak of the Last Glacial Maximum, conventionally dated in global terms to about 26,500–19,000 years ago. The last Irish ice sheet expanded and reorganised over a long period, and its extent differed from region to region. Later glacier movement also eroded, buried and dispersed earlier deposits. This is one reason why the Irish record for the period is so much thinner than that of France, Iberia, southern Britain or central Europe.
Ireland was within the last glacial period, but it should not simply be pictured as a country buried continuously beneath ice. The scale, timing and regional pattern of ice growth remain active subjects of research. Some evidence indicates that north-central Ireland retained ice-free ground until at least about 34 ka, while reworked marine shells suggest open water off north-western Ireland during portions of the preceding millennia. Other work argues for more extensive ice-sheet growth during the wider last cold stage. The most secure conclusion is that this was a transitional, climatically unstable world: ice was advancing in some sectors, but the island’s cover was neither uniform nor fixed at a single moment.
Ireland was entering a period of profound climatic deterioration. The Last Glacial Maximum itself lay ahead, conventionally placed at roughly 26,000–19,000 cal BP, but ice sheets were already growing across the north-west European margin. Reconstructions differ over precisely when particular Irish districts became ice-covered and how far ice extended at successive stages. That uncertainty is important: it rules out a single, confident map for 31,972 BCE. Nevertheless, the broad sequence is secure. Ireland was not yet the wholly ice-dominated land it would become later in the glaciation, while the advancing cold was reshaping habitats, river systems, coastlines and routes of animal movement.
Ireland lay in a changing Ice Age landscape. The great British–Irish Ice Sheet had not yet reached its fullest later extent, but ice was building in northern and upland regions, and conditions were becoming increasingly severe. Modern reconstructions stress that the precise limits of ice around 31,000 years ago remain uncertain because direct dates are sparse. They nevertheless indicate expanding ice in parts of the British and Irish region, with substantial regional variation rather than one simple, unchanging blanket of ice. The Last Glacial Maximum came later, broadly between about 26,000 and 19,000 years ago, when much or all of Ireland was likely glaciated.
This was before the Last Glacial Maximum, the phase when the last Irish Ice Sheet reached its greatest overall extent. It was not, however, a benign interval. The climate of MIS 3 was unstable, marked by sharp cold episodes and warmer interstadials. Ice sheets, glaciers, sea level, vegetation and animal ranges changed repeatedly over timescales far longer than a single human lifetime but short in geological terms.
