Geoscience Reference
In-Depth Information
years ago. He argued that the denudation rate of 1 inch per century
cited byDarwinwas incorrect and that the rate would have been closer
to 1 inch per annum. Taking the Ganges and Brahmaputra rivers and
the Bay of Bengal as an example he said that the ocean was fed with
6,368,077,440 cubic feet of sediment each year which would cover the
floor of the Bay of Bengal with just under one-hundredth of an inch.
Taking Ramsay's thickness he converted it into inches and the result-
ing division of 864,000 inches by the annual thickness of sediment
deposited by the Ganges/Brahmaputra gave 95,904,000 years. He did
note some problems with this method and was aware that the mon-
soon effects on erosion dumped more sediment into the Ganges/
Brahmaputra than would be found in most other rivers. He then
modified the length of time because the surface of the Earth had
been 20 8C hotter in the past that it was at the present. This hotter
environment would have created more atmospheric moisture and so
the effect of rain and river flow would have been greater in the past.
This reduced the time needed to deposit the Cambrian to Recent
sediments by nearly 32 million years to 63,936,000 years. Finally,
further modifications to this number were needed to take into account
the differences in tectonic activity between the ancient past and
younger times. Phillips argued that the surface of the Earth in its
infancy was prone to greater uplift, movement and folding and there-
fore more rocks were subjected to erosional forces. This necessitated
reducing the figure to 38 million years.
In other words, although the calculation was not quite so sim-
plistic, Phillips had determined the thickness of the sedimentary pile
and using various figures for the varying rates of sedimentation
through time had arrived at this figure. In terms of scientific history
this was an important calculation. It was the first time that such a
method had been employed for the purpose of determining the Earth's
age. It also came at a time when other scientists, equally displeased
with Darwinian ideas, were devising thermal methods of dating the
Earth. This methodology was championed by WilliamThomson, who
was supported in his views by John Phillips.
