Three of Iceland.s large, permanent ice fields are visible in this Moderate Resolution Imaging Spectroradiometer (MODIS) image from June 21, 2002. The largest, Vatnajokull (right), covers several active volcanoes, whose activity crate vast meltwater lakes in the volcanoes. calderas beneath the glacier.s surface. Eventually the calderas overflow, giving rise to massive glacial outburst floods. To the west of Vatnajokull is Hofsjokull, and to its west is Langjokull. A few bright blue-green lakes can be seen dotting the thawing landscapes of western Iceland. These lakes are bright because glacial runoff fills them with highly reflective sediment, ground very finely by the massive weight of glaciers.