At this time England south of the Bristol Channel (the estuary of the Severn), and the Thames, appears to have been above water. The northern part of the country, and the high-ground generally of Britain and Ireland were covered with gliding glaciers, by whose grinding action the whole surface became moulded and worn into its present shape, while the floating icebergs which broke off at the sea-side from these glaciers, conveyed away and dropped on the bed of the sea those fragments of rocks and the gravel and other earthy materials which are now generally recognised as glacial accumulations.
In all directions, however, proofs are being gradually obtained that, about this period, movements of submersion under the sea were in progress, all north of the Thames.
XXIX.—Ideal American Landscape in the Quaternary Epoch.
Ramsay points out indications, first of an intensely cold period, when land was much more elevated than it is now; then of submergence beneath the sea; and, lastly, re-elevation attended by glacial action. “When we speak of the vegetation and quadrupeds of Cromer Forest being pre-glacial,” says Lyell, “we merely mean that their formation preceded the era of the general submergence of the British Isles beneath the waters of the glacial sea. The successive deposits seen in direct superposition on the Norfolk coast,” adds Sir Charles, “imply at first the prevalence over a wide area of the Newer Pliocene Sea. Afterwards, the bed of the sea was converted into dry land, and underwent several oscillations of level, so as to be, first, dry land supporting a forest; then an estuary; then again land; and, finally, a sea near the mouth of a river, till the downward movement became so great as to convert the whole area into a sea of considerable depth, in which much floating ice, carrying mud, sand, and boulders melted, letting its burthen fall to the bottom. Finally, over the till with boulders stratified drift was formed; after which, but not until the total subsidence amounted to more than 400 feet, an upward movement began, which re-elevated the whole country, so that the lowest of the terrestrial formations, or the forest bed, was brought up to nearly its pristine level, in such a manner as to be exposed at a low tide. Both the descending and ascending movement seem to have been very gradual.”
