Photo Captions 1. Cirque glacier Cathedral Glacier, a small cirque glacier in British Columbia, Canada. 2. Valley glacier The Mont Miné Glacier in the Swiss Alps. Note the arcuate crevasses around a subglacial channel on the left-hand side of the glacier margin, and the thick mantle of supraglacial sediment on the right-hand side associated with rockfall from the adjacent mountainside. 3. Hanging glacier This photo shows a small tributary glacier dropping steeply from its “hanging valley” to join the Gilkey Glacier in Alaska. Similar hanging valleys associated with past glacial activity are common in the uplands of Britain. 4. Outlet glacier Outlet glaciers often appear similar to ordinary valley glaciers, but differ in that they are fed by ice from a nearby ice cap or ice sheet. The photo is of Svinefellsjökull, a small outlet glacier associated with an icefall from Oraefajökull, the ice cap visible in the background. 5. Ice sheet Aerial view of the Greenland Ice Sheet. Note how the underlying topography has been almost completely buried by the overlying ice, with only the highest mountain tops appearing as nunataks. 6. Rigid-bedded glacier Glaciers can be subdivided according to substrate over which they flow (see also photo 7). This in turn affects their characteristics, including their speed, their ability to erode and deposit and consequently their landform record. Rigid-bedded glaciers rest on bedrock and are associated with features such as striations (photo 16) and roche moutonées. This photo shows the rigid-bedded margin of the Mendenhall Glacier in Alaska. 7. Soft-bedded glacier Many glaciers flow over unconsolidated, sediment, rather than rigid bedrock. This photo shows the margin of Skeiðarárjokull, a large-outlet glacier in southern Iceland that terminates on a large outwash plain or sandur. The ability of these soft-bedded glaciers to deform the sediments over which they flow has important implications for their motion and landforms they produce. Soft-bedded glaciers are associated with a variety of sedimentary landforms including flutes (photo 17), drumlins (photo 18) and crevasse-fill ridges (photo 19). 8. Accumulation Glaciers are sustained by the accumulation of snow in their upper reaches (accumlation area). This photo of a snow pit indicates one year’s accumulation of snow (c. 6 m) in the upper part of the Juneau Icefield, Alaska. 9. Glacier calving In addition to ablation, glaciers can also lose mass via calving into large water bodies. This aerial view of the margin of Breiðamerkurjökull in Iceland illustrates the calving of icebergs into the large proglacial lake, Jökulsarlon. Note the intense crevassing of the margin associated with accelerating ice flow. 10. Supraglacial streams Melting of snow and ice on the upper surface glaciers in summer can create large stream channels incised into the ice. This photo shows a large supraglacial channel on the surface of the Gilkey Glacier, Alaska (ice-axe for scale). Note the cusps cut into the channel walls that show previous high water levels. 11. Ogives and medial moraines This photograph of the Gilkey Glacier, Alaska shows a series of ogives (the wave-like features running from right to left) and medial moraines. The ogives are associated with ice flow down icefalls (one is located just off the photo to the right), with one ridge and depression corresponding to one year’s ice flow. The medial moraines mark the boundaries of converging streams of ice. 12. Crevasses Crevasses are associated with fracture of the brittle upper layers of ice during glacier flow. This area of intense crevassing is associated with rapid ice motion during the 2000 surge of Dyngjujökull, an outlet glacier of Vatnajökull in Iceland. Note also the small supraglacial lake in the bottom left of the photo. 13. Basal ice Glaciers are rarely comprised entirely of clean, blue ice. Instead, they are often characterised by a debris-rich basal zone known as the basal ice layer. This photo shows a debris-rich basal ice layer at the base of the Leverett Glacier in western Greenland. 14. Subglacial zone The majority of glacial landforms are produced at the glacier bed (the subglacial zone), where processes of erosion, transport and deposition are at their most active. This image shows a subglacial cavity beneath the Ferpècle Glacier in the Swiss Alps (ice-axe for scale; ice is flowing towards the viewer). Note the large quantities of fine- grained sediment (“rock flour”) plastering the glacier’s sole, associated with basal sliding and erosion of the underlying bedrock. 15. Striations Striated bedrock located close to Yellowknife in the Canadian Northwestern Territories. These striations were produced by the Laurentide Ice Sheet, a huge ice mass comparable in size with the Antarctic Ice Sheet that covered most of North America during the various “ice ages” of the Quaternary Period (last 2 million years). 16. Moraines Large end moraine associated with deposition at the margin of the Russell Glacier, a large outlet glacier in western Greenland. 17. Flutes This seemingly corrugated surface at the margin of Skeiðarárjokull, southern Iceland, is characterised by a series of flutes. These linear, parallel ridges of sediment are usually associated with an obstacle at their up-glacier end (usually a large clast), and are formed by the squeezing of sediment into groove carved in the underside of the glacier as it flows over the immobile obstacle. 18. Drumlins Drumlins represent one of the best known landforms produced by glaciers. These small, streamlined hills are associated either with subglacial erosion into pre-existing materials or the active deposition of new sediment. These small drumlins being exposed by ice-marginal retreat, are associated with 1991 surge of Skeiðarárjokull, southern Iceland. 19. Crevasse-fill ridges Crevasse-fill ridges at the margin of Eystri-Hagafellsjökull, central Iceland. These features are associated with the injection of saturated, deformable subglacial sediments into basal crevasses, and are considered by some to be diagnostic of glacier surges (these examples are associated with a surge in 1999). 20. Till Glaciers are associated with distinctive sediments as well as distinctive landforms. Glacial till is associated with direct deposition from a glacier (in the absence of meltwater) and is characterised by a broad range of particle sizes (hence the old term boulder clay) and lithologies, and a lack of sorting. This example is from Skipsea on the Holderness Coast, Yorkshire.