Last Ice Age

The Last Ice Age is the geological reference point through which the novel explains how changes in sea level and pressure can unsettle methane hydrates and continental slopes. At its peak, about 18,000 years ago, sea level stood roughly 120 metres below its level at the beginning of the third millennium; the resulting changes reshaped marine environments and helped make the seabed unstable. The period matters to the story because its geological consequences persist beneath a modern world inclined to mistake calm for safety.

Sea-Level Change and the Continental Shelves

At the peak of the Last Ice Age, a large share of the world’s water was locked in glaciers. With less water in the oceans, pressure on the continental shelves fell. Some seas had not yet formed, while others became shallower or dried out, leaving extensive marshland. The novel places these changes within the geography of the continental shelf: the relatively shallow underwater continuation of the continental plate, which can extend far from land before descending toward the deep ocean.

The contrast between that altered landscape and the later world is also human in scale. Sveggesundet, in the Norwegian fjord landscape, is described as one of the first places settled after the Last Ice Age. Elsewhere, the account emphasizes that the modern North Sea is geologically young, in its present form dating back barely ten thousand years. The landscapes and waters familiar to people are therefore recent features against a much longer history of environmental change.

Hydrate Instability and Slope Failure

The reduced pressure of glacial periods affected gas hydrates beneath the sea. These ice crystals had trapped and compressed methane; when they melted, methane escaped and expanded to 164 times its former volume. The novel compares the hydrates’ changing role to a reversal: for thousands of years they had helped hold slopes together, but their destabilization turned that support into a source of disruption. As gas forced its way through sediment, it opened crevices and craters and left the seabed porous and unable to support its own weight.

The consequences extended beyond the seabed. Continental slopes collapsed, carrying sections of shelf and great quantities of debris hundreds of kilometres into the depths. Methane entering the atmosphere also contributed to severe climate change. The Last Ice Age thus connects climatic shifts to geological failure and, in turn, to effects reaching coastlines and islands; a change in pressure below the sea becomes a hazard on a much larger scale.

Geological Evidence and Storegga

Scientists identified traces of repeated landslides off central Norway in the second half of the twentieth century. The evidence records substantial loss of slope over more than 40,000 years. The novel attributes the failures to more than one set of conditions: warmer periods raised the average temperature of currents near the slope, while glacial periods could leave the water cold but reduce pressure. In this account, stable hydrate conditions are the exception in geological time, rather than a permanent baseline.

The scale of the past failures makes that history concrete. More than 5,500 cubic kilometres had been torn from the Norwegian shelf, and sediment formed a trail over 800 kilometres long in the sea between Scotland, Iceland, and Norway. The largest slide had occurred within the previous 10,000 years and was named the Storegga seabed slide. These measurements give the geological account a present-tense implication: the modern world occupies a temporary interval of apparent stability, not a guarantee that the processes which shaped the seabed have ended.

Deep Time and Modern Vulnerability

The Last Ice Age’s narrative significance lies in the way it unsettles the assumption that the contemporary ocean is fixed and benign. The novel explicitly contrasts geological instability with people’s willingness to treat calm as normal. Later, it describes a continental-slope collapse in which the downward movement lowers sea level over a broad area and displaces water outward in a wave. The ancient history does not make that later event identical to the glacial-era slides; rather, it supplies a long geological context for the destructive possibilities of slope failure.

That perspective also broadens the book’s sense of the ocean as a human environment. The continental shelf is comparatively familiar and heavily inhabited, while the depths beyond it remain difficult to know. By tracing present danger back through glacial sea-level change, methane release, and ancient landslides, the Last Ice Age marks the limit of a short human timescale: landscapes that seem settled and stable can be only a brief phase in a changing marine world.