Icelanders are shown to have had a greater knowledge and experience of glaciers than most nations, from the time of settlement through to the 18th century, and they were sometimes pioneers in glaciological studies. The first written accounts of glaciers can be traced back to the 12th century, and the connecting of ice masses with climate is dated to the mid-13th century. The first map showing glaciers was drafted in Iceland in 1570, and in 1580 glaciers were reported to be expanding due to a deteriorating climate. In 1695 the Icelandic scholar Þorður Vidalin wrote a thesis in which he hypothesised about how and why glaciers move. By the 1790s, Icelandic natural scientists had categorised the various kinds of glaciers and Sveinn Palsson had described glacial surges, correctly surmising that ice was a viscous material. A history of the expeditions of many scientists and travellers from Iceland, Scandinavia and Europe, from the mid-19th to mid-20th century, then follows, as they explored and studied Icelandic glaciers and their environments and the effects of subglacial volcanic activity. Since the mid-20th century, the use of motorised vehicles and aircraft, together with the intensified efforts of the Iceland Glaciological Society, have enabled greater access to, and a more accurate mapping of glaciers, as well as the continuous, systematic research of Icelandic ice masses. The meteorological and glaciological data gleaned from this research in Iceland, it is asserted, can now help predict future effects of climate change on both temperate and polar ice masses.