Ice and our landscape

British ice coverage during the most recent glaciation – the 'Devensian'

Britain has not always enjoyed its current mild climate, over the past 2.6 million years it has gone through extremes of cold ice ages and warm interglacials in a period of geological history that we call the Pleistocene.

What is an ice age?

An ice age in fact often refers to a group of several cold periods that take place over a relatively short period of time.

Today, 10 per cent of the world is covered by ice but that figure has been as high as 30 per cent in the past.

One ice sheet, reached as far south as London, and in places the ice was three miles thick.

Humans and ice ages

Interlinked with the fluctuating ice sheets is the story of human evolution.

Humans first arrived in Britain at least 780 000 years ago and they have recolonised after major glaciations to leave a pattern of occupation closely related to the climate.

These early people began to use items they found lying around as tools and gradually they learnt to make their own tools like these Stone Age tools made from worked flints.

Neolithic Skull
Hand axe
Flint tool

Tools like these could be used for butchering animals and for extracting the valuable high protein marrow out of the bones.

A wide variety of animals have lived in Britain ranging from giant mammoth in the cold periods to hyena and even rhinoceros in the interglacials.

It is quite common for remains of animals such as the sabre-toothed cat, woolly mammoth, wolf, hyena, elk, bison and bear to be found in caves around the country. See The Bone Caves.

These fossilised hazelnuts were found in a submerged forest, one of them still bears the evidence of being nibbled!
Fallow deer and elk.

Modern-day glaciers

Ice coverage in the world today

Today, glaciers and ice sheets are found at extreme latitudes like the north and south poles and high altitudes such as the Himalayas and the Alps.

Much of Britain has been shaped by ice, with the last glaciers still clinging on in the Highlands of Scotland until around ten thousand years ago. The main body of ice had dispersed about four thousand years previously.

Several reasons have been suggested for the cyclic nature of ice ages, although it is agreed that it cannot be attributed to a single cause.

The most widely accepted is the theory of Milankovich cycles, named after Milutin Milankovich, the Serbian scientist who suggested them. His theory was that the changes are caused by a combination of effects: alterations in the shape of the Earth's orbit around the Sun from nearly circular to much more elliptical; a change in the tilt of the Earth's rotational axis; and variations in the direction of the axis of rotation.

These effects are known scientifically as eccentricity, obliquity and precession.

Eccentricity, Obliquity and Precession

Modern glacial features

Post glacial features

Tasman glacier in New Zealand

How do glaciers evolve?

Glaciers are not static objects, they move very slowly, flowing under the weight of ice, and they grow and shrink, depending on the climatic conditions.

If there is a greater amount of snowfall and low temperature then this will cause a glacier to grow as the snow is compressed into ice.

In warmer periods the ice can melt and calve, forming icebergs and causing the glacier to shrink.

Glacier ice contains water, air bubbles, sediments and sometimes even trapped plants and animals.

The water within the ice helps the glacier to move and slide over the ground. It also moves by moulding like plasticine and by passing over a softer substance like sand or gravel.

In an area which has been glaciated, such as Britain, you can find evidence that glaciers were present not that long ago (geologically speaking).

The BGS is studying present-day glaciers in Virkisjökull, Iceland