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Information on Glaciation

What glaciation means

Glaciations are characterized by cool, wet climates and thick ice sheets extending from each
pole. Mountain or alpine glaciers in otherwise unglaciated areas expand and extend to lower
elevations even in the lowest of latitudes. Sea levels drop due to the presence of large

volumes of water above sea level in the icecaps. There is evidence that ocean circulation
patterns are disrupted by glaciations. Since the earth has significant continental glaciation
in the Arctic and Antarctic, we are currently in a glacial minimum of a glaciation. Such a
period between glacial maxima is known as an "interglacial". The current one is the Flandrian.

In general, the Earth seems to have been ice-free even in high latitudes except during
relatively rare glacial maximums such as the one from which we emerged 10 to 15 thousand

years ago.

The causes of glaciations have been much debated ever since the phenomenon was clearly
identified in the 17th century. Modern theories tend to revolve around periodic oscillations in
the Earth's orbit, hypothesized periodic changes in solar output, changes in atmospheric
circulation due to mountain orogenies, and/or the effects of continental masses drifting into

polar regions where Antarctica currently resides.

Newer means of detecting glaciations

The problem of the removal of evidence of earlier glacials by the later ones has been
overcome to some extent by drilling cores of ice and of benthic mud. The ice of an ice cap
contains bubbles of the atmosphere of the time when it was trapped. In so far as a high

proportion of carbon dioxide represents an interglacial, it is possible to analyze the gas in
the bubbles and see when the warmer periods were.

On the other hand, ice is solid water. A water molecule includes an oxygen atom but some
isotopes of oxygen are more readily incorporated into ice crystals than others. Thus, when
these are locked up in ice caps, they are rarer in the remaining waters of the world. This is

detectable in the layers of mud laid down each year in the ocean depths. Therefore, oxygen
isotope variation in the mud varies with time and with the extent of the process of glaciation.
As far as they go, the three sources of information, the traditional, the carbon dioxide
proportion and the oxygen isotope tend to corroborate each other though the newer ones
appear to show more detailed fluctuation in glaciation.

Upland glacial features include:

Corrie - This is an arm chair shaped hollow found in the side of a mountain, e.g. Helvellyn,

Lake District

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