Page 287 - Fundamentals of Geomorphology

270 PROCESS AND FORM

Plate 10.14 Esker made up of slightly deformed stratified sands and gravels near the ice margin of Comfortlessbreen,
Svalbard.
(Photograph by Mike Hambrey)

of sand and gravel and laid down in a meltwater tunnel as the ice. Lakes may form before the overflow occurs.
underneath a glacier. Some eskers form at ice margins, Until the mechanisms of subglacial drainage were under-
and are not to be confused with kames and kame terraces stood, channels found in formerly glaciated temperate
(see below), which are ice-contact deposits at the ice mar- regions were ascribed to meltwater overflow, but many
gin.Inthepast,confusionhasbesettheuseoftheseterms, of these channels are now known to have been wrought
but the terminology was clarified in the 1970s (see Price by subglacial erosion.
1973 and Embleton and King 1975a). Eskers can run
uphill and sometimes they split or are beaded. They may
run for a few hundred kilometres and be 700 m wide Kames
and 50 m high, although they are typically an order of The main depositional landforms associated with ice
magnitude smaller.
margins are kames of various kinds (Figure 10.7).
Crevasse-fillings, which comprise stratified debris that
Ice-margin landforms entered crevasses through supraglacial streams, are minor
Meltwater and overflow channels landforms. Kames are commonly found with eskers.
They are flat-topped and occur as isolated hummocks,
Erosion by meltwater coursing alongside ice margins as broader plateau areas, or, usually in proglacial set-
produces meltwater channels and overflow channels. tings, as broken terraces. Individual kames range from
Meltwater channels tend to run along the side of a few hundred metres to over a kilometre long, and a few
glaciers, particularly cold glaciers.They may be in contact tens of metres to over a hundred metres wide. They have
with the ice or they may lie between an ice-cored lateral no preferred orientation with respect to the direction of
moraine and the valley side. After the ice has retreated, ice flow. If many individual kames cover a large area, the
they can often be traced across a hillside. term ‘kame field’ is at times applied.
Overflow channels are cut by streams at the ice mar- Kame terraces develop parallel to the ice-flow direc-
gin overtopping low cols lying at or below the same level tion from streams flowing along the sides of a stable or