Ice through the Ages
Today around 90% of the ice on land is found on the Antarctic continent around the South Pole. The second largest mass is the ice sheet of Greenland, near the North Pole. The rest of the land ice, as we have seen, is spread among the smaller ice caps of the Canadian or Siberian Arctic and in the form of mountain glaciers that remain only in high altitudes in tropical or equatorial regions. The polar regions thus constitute the preferred habitat of the planet’s ice.
The idea that the situation could have been different in the past and that in certain periods more ice was present on the continents is rather recent. First expressed in the first half of the nineteenth century, this theory aroused considerable disbelief in the field, and it took thirty years for its proponents, including Louis Agassiz, to convince the community of geologists of the existence of past glaciations.
If you go to Chamonix today, there is a good chance that someone will tell you the story of the Mer de Glace, which reached the valley at the end of the nineteenth century. Since then, the glacier’s front has retreated by a kilometer and a half, leaving in its wake erratic piles of rocks that make up moraines. The discovery of the existence of glaciations was born out of the investigation of such moraines. Until the eighteenth century, geologists, called diluvionists, believed that these rocks had been transported great distances by the flood described in the Bible. It wasn’t until the following century that this explanation was questioned and the notion of great glaciations occurring in the past was proposed. John Imbrie, professor of oceanography at Brown University, combined his talents as a scientific storyteller with those of his