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7. The Ice Age

In con­trast to the other geo­lo­gi­cal units, the cau­se for and the effect of the ice age is limi­ted to the sur­face and it is not lin­ked to tec­to­nic pro­ces­ses – at least regio­nal­ly. Neit­her did it lea­ve huge rock­mas­ses, com­pa­red to other chap­ters of Earth histo­ry. But it shaped Green­lands land­s­cape to an extent which makes it fair to say that it crea­ted Green­land and its uni­que cha­rac­ter and beau­ty. More important than the sedi­ments which have been and, in pla­ces, still are depo­si­ted by gla­ciers, rivers etc., may be the strong effect of ero­si­on which shaped the land­s­cape so dra­ma­ti­cal­ly. In Green­land, the ice age is not over yet: it is still 85% cove­r­ed with ice.

Moraine at the rim of the inland ice (Kangerlussuaq, West Greenland)

Morai­ne at the rim of the inland ice (Kan­ger­lus­suaq, West Green­land)

The onset of gla­cia­tí­on in Green­land may have star­ted about 7-8 mil­li­on years ago. The inland ice has exis­ted sin­ce then pro­bab­ly without inter­rup­ti­on, but cer­tain­ly with some fluc­tua­ti­on regar­ding volu­me and extent. The histo­ry of the­se fluc­tua­tions is, for most of it, not known in any detail, as the gla­ciers tend to dele­te their own traces. But cer­tain­ly Green­land has been com­ple­te­ly ice-cove­r­ed bey­ond its pre­sent-day coast­li­ne at mul­ti­ple times, at about 130 000 years ago for the last time. Jame­son Land soon beca­me ice-free sin­ce then and has at least part­ly remai­ned so until today, which has been important for the sur­vi­val of several plant spe­ci­es in the area.

The last gla­cia­ti­on peak was about 15-10 000 years ago, with gla­ciers reaching far bey­ond their pre­sent limits. Most land are­as in the Scores­by­sund were ice cove­r­ed bey­ond today’s coast­li­ne, only the wide, midd­le part of the fjord (Hall Bred­ning) and its ent­ran­ce south Liver­pool Land have been ice free, tog­e­ther with sou­thern and wes­tern Jame­son Land. Sin­ce then, the gla­ciers have retrea­ted, with some fluc­tua­tions, until they reached today’s posi­ti­on. A last pha­se of gene­ral advan­ce was around 1850 during the ‘litt­le ice age’, sin­ce then the gla­ciers are retrea­ting, as they do cur­r­ent­ly almost ever­y­whe­re on Earth. This beco­mes obvious from lar­ge, fresh morai­nes near almost all gla­ciers.

Gla­ciers lea­ve sedi­ments behind: Morai­nes and erra­tic boul­ders. A morai­ne is any kind of ‘gla­cier dirt’ depo­si­ted by gla­cier ice, whe­re­as erra­tic boul­ders are sin­gle rocks left by gla­ciers that have long disap­peared in the land­s­cape. An erra­tic boul­der may be the last remains of a morai­ne which has other­wi­se been was­hed away. Thin, old morai­ne sedi­ments and erra­tic boul­ders can be found almost any­whe­re in Green­land in the ice-free are­as.

Erratic boulder in Rypefjord, inner Scoresbysund

Erra­tic boul­der in Rypefjord, inner Scores­by­sund

Much more important for the recent appare­an­ce of the Scores­by­sund has been the inten­se ero­si­on of the ice-age gla­ciers. It was this ero­si­on which has crea­ted the lar­gest fjord sys­tem in the world (rivers may have made a start befo­re the onset of the ice age, though). In its inner bran­ches, depths of more than 1000 metres are com­mon and reach up to 1400 metres in pla­ces! To both sides of the fjords, rock­walls hig­her than 1000 metres and moun­tains reaching bey­ond 2000 metres are towe­ring. The spec­ta­cu­lar alti­tu­de dif­fe­ren­ces, which are so evi­dent in the dra­ma­tic moun­tain and fjord sce­ne­ry of the inner Scores­by­sund and – on a some­what smal­ler sca­le – in Liver­pool Land, is a result of strong land uplift during the ope­ning of the Atlan­tic oce­an and sub­se­quent gla­cier ero­si­on.

Steep rock­walls crea­ted by ice-age gla­ciers in the Maria­ger Fjord,
Liver­pool Land

Steep rockwalls created by ice-age glaciers in the Mariager Fjord, Liverpool Land

Gra­ni­tic boul­der cra­cked by frost action (Ant­arc­tic Pen­in­su­la), a type of wea­the­ring which is also very com­mon in Green­land. Size of boul­der ca. 1 m (left-right).

Granitic boulder cracked by frost action (Antarctic Peninsula)

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last modification: 2013-10-12 · copyright: Rolf Stange
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