GLACIAL AND GLACIOFLUVIAL LANDSCAPES - Fundamentals of Geomorphology

Geology Reference

In-Depth Information

addressed by relying on the low permeability of

the till and reworking the till around the edges

of the site to remove potentially leaky sand-lenses

in its upper layers. In August 1993, after a public

inquiry into the Hardwick site, planning permis-

sion was refused, partly because knowledge of the

site's geology and land drainage was inadequate and

alternative sites were available. Research into the site

prompted by the proposal suggested that leachate

containment was a real problem and that Norfolk

County Council was mistaken in believing that the

till would prevent leachates from leaking. It also iden-

tified other sites in south Norfolk that would be

suitable landfill sites, including the extensive sand

and gravel deposits along the margins of the River

Yare and its tributaries. Landraising in a till plain

is also unwelcome on geomorphological grounds,

unless perhaps the resulting hill should be screened

by woodland. A lesson from this case study is that

knowledge of Quaternary geology is central to the

planning and design of landfill in areas of glacial

sediments.

SUMMARY

shrink the cryosphere and destroy Quaternary landforms.

Conversely, knowledge of Quaternary sediments is indis-

pensable in the judicious use of glacially derived resources

(such as sands and gravels) and in the siting of such

features as landfill sites.

Ice covers about 10 per cent of the land surface, although

18,000 years ago it covered 32 per cent. Most of

the ice is in polar regions. Glaciers come in a variety

of forms and sizes: inlandsis, ice sheets, ice caps, ice

shelves, ice shields, cirque glaciers, valley glaciers, and

other small glaciers. Glaciers have an accumulation zone,

where ice is produced, and an ablation zone, where ice

is destroyed. Erosion by ice creates a wealth of land-

forms by abrasion, by fracture, by crushing, and by

eroding a mountain mass. Examples include glacially

scoured regions, glacial troughs, striated bedrock, trough

heads, cirques, flyggbergs, crescentic gouges, horns, and

nunataks. Debris laid down by ice produces an equal

variety of landforms. Supraglacial deposits form lat-

eral moraines, medial moraines, dirt cones, erratics, and

many more features. Subglacial forms include drumlins

and crags-and-tails. Terminal moraines, push moraines,

hummocky moraines, and other forms occur at ice mar-

gins. Meltwater, which issues from glaciers in copious

amounts during the spring, cuts valleys and deposits

eskers beneath the ice, produces meltwater channels and

kames at the edge of the ice, and fashions a variety

of landforms ahead of the ice, including spectacular

scablands and spillways, outwash plains, and, on a

much smaller scale, kettle holes. A variety of paraglacial

landforms develop immediately glaciers melt. Humans

interact with glacial landscapes. Their current industrial

and domestic activities may, through global warming,

ESSAY QUESTIONS

1 How does ice flow?

2 How does ice fashion landforms?

3 Appraise the evidence for

catastrophic glaciofluvial events.