Man and the Glacial PeriodWright, G. Frederick (George Frederick)
History
Man and the Glacial Period
Wright, G. Frederick (George Frederick)
Glacial epoch; Prehistoric peoples
"Returning now towards the head of the glacier we may follow with
advantage its left bank downward. The ice-flow on the Cumberland coast
appears to have resembled very much that in North Wales. A great press of
ice from the northward (Galloway) seems to have had a powerful 'easting'
imparted to it by the conjoint influences of the thrust of the Irish ice
and the inflow of ice from the Clyde. Whatever may have been the cause,
the effect is clear: about Ravenglass cleavage took place, and a flow to
northward and to southward, each bending easterly. By far the larger mass
took a southerly course and bent round Black Combe, over Walney, and a
strip of the mainland about Barrow in Furness, and out into and across
Morecambe Bay. Its limits are marked in the field by the occurrence of
the same rocks which characterise it in Anglesea, viz., the granites of
Galloway and of west and central Cumbria.
"The continued thrust shouldered in the glacier upon the mainland of
Lancashire, but the precise point of emergence has not yet been traced,
though it cannot be more than a few miles from the position indicated on
the map. I should here remark, that all along the boundaries the Irish
Sea Glacier was confluent with local ice, except, probably, in that part
of the Pennine chain to the southward of Skipton. Down to Skipton there
was a great mass of Pennine ice which was compelled to take an almost
due southerly course, and thus to run directly athwart the direction of
the main hills and valleys. A sharp easterly inflection of the Irish Sea
Glacier carried it up the valley of the Ribble, and thence, under the
shoulder of Pendle, to Burnley, where Scottish granites are found in the
boulder-clay.
"On the summit of the Pennine water-shed, at Heald Moor, near Todmorden
(1,419 feet), boulder-clay has been found containing erratics belonging
to this dispersion; while in the gorge of the Yorkshire Calder, which
flows along the eastern side of the same hill, not a vestige of such a
deposit is to be found, saving a few erratic pebbles at a distance of
eight or ten miles, which were probably carried down by flood-wash from
the edge of the ice.
"From this point the limits of the ice may be traced along the flanks of
the Pennine chain at an average altitude of about 1,100 feet.
"At one place the erratics can be traced to a position which would
indicate the formation of an extra-morainic lake having its head at a
col about 1,000 feet above sea-level, separating it from the valley of
an eastward-flowing stream, the Wye, about twelve miles down which a few
granite blocks have been found. Other extra-morainic lakes must have
been formed, but very little information has been collected regarding
them. The Irish Sea Glacier can be shown to have spread across the whole
country to the westward of the line I have traced, and beyond the estuary
of the Dee.
Public-domain text, read in full here on John Shaqi.
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