20 | Great Geologists
James Hutton
One day in 1788 three eminent gentlemen intellectuals from
Edinburgh set off in a boat along the coast of south-eastern
Scotland, south of Dunbar and not too far from the English
border. They landed at Siccar Point, a rocky promontory jutting
into the North Sea. One of the party expounded to the others
his interpretation of the rock formations forming the foreshore
in front of them. He observed near-vertically arranged grey
shale beds overlain by reddish sandstones lying at an angle
closer to horizontal, thus the shales and sandstones were
separated from each other by a distinct angular discordance.
To the speaker in the landing party, this succession implied
that the shales had been deposited on an ancient sea-bed
over a long period of time, that they had then been buried and
solidified, then uplifted by forces within the Earth, tilted and
eroded, and then the sandstones had been deposited upon
the eroded surface and then in turn solidified and uplifted. This
process must have taken a huge amount of time, much longer
than the commonly accepted wisdom in the 18th century
that the Earth was a few thousand years old based on a literal
interpretation of biblical events. John Playfair, the celebrated
mathematician who was at Siccar Point that day, wrote that on
hearing of this explanation that the “the mind seemed to grow
giddy by looking so far into the abyss of time”. The person
who gave the explanation that this rock succession implied the
vastness of geological time was James Hutton – the founder
of modern geology.
James Hutton was born in Edinburgh in 1726 and although
he studied medicine, he developed interests in chemistry,
meteorology and agriculture. He displayed an intellectual
curiosity into a diversity of subjects that typified many of the
Scottish Enlightenment scholars in the second half of the 18th
century. He developed a means to extract salts from coal
soot that could be used in cloth dyeing (and earned a healthy
income from this), wrote a “Theory of Rain” that preceded
much modern meteorological thought on the hydrological
cycle, and acquired a large farming estate which encouraged
him to study modern agricultural methods. It was farming that
really ignited his interest in geology as he noted the formation
of soils and their erosion and subsequent transport into the sea
by streams was a progressive, long-term, process and one that
was cyclic – the sediments that were deposited were formed
into rocks, uplifted and eroded again.
By 1753 he was able to write “I have become very fond of
studying the surface of the Earth and am looking with anxious
curiosity into every pit or ditch or river bed that falls my way”.
He was now travelling far and wide in England, Scotland and
Wales to make geological observations and as he did so he
collected fossils and observed what we would call today
sedimentary structures (such as ripple marks) giving him the
idea that some rocks were the product of deposition in ancient
seas and that sedimentary processes that were taking place
on Earth today had taken so in the past. This was the concept
of Uniformitarianism or “the present is the key to the past”
that was later expounded upon by Sir Charles Lyell. Moreover,
Hutton viewed the history of the Earth to be markedly cyclic
– it could not simply be progressively eroding away since
its creation. Instead there were repeated cycles of erosion,
James Hutton painted by Sir Henry Raeburn in 1776.