Environmental Engineering Reference
In-Depth Information
near-surface drainage become increasingly important towards the margins. Weak,
sporadic permafrost activity is still present in British mountains for these reasons,
although in other respects Britain lies outside the circumpolar permafrost zone.
CLIMATE, TECTONICS AND ICE AGES
Links between snowfall and temperature make the ELA a vital measure of glacier
climate. It lies close to sea level in polar regions today, rising away from the poles so
that, for example, it lies at some 1.5 km above sea level in northern Britain, 3 km in the
European Alps and 5 km at the equator. This is why Britain is just ice-free but there are
small glaciers on equatorial mountains in East Africa (see Figure 25.9). However, we
know from geomorphic, biological and oxygen isotope evidence that Quaternary ELAs
were often low enough for global or local glaciation
Figure 15.4
Modern distribution of permafrost in the
northern hemisphere.
Source: After Ballantyne and Harris (1994).
THERMODYNAMIC CHARACTER OF GLACIERS
key concepts
There are clear links between glacier climate, mass balance and rates of flow which
collectively define a glacier's
thermodynamic state
(Table 1) and hence geomorphic
activity. Polar climates are so cold that relatively little snow falls or melts, ice takes
longer to accumulate and flow velocity varies from zero (where the glacier is frozen to its
