Geoscience Reference
In-Depth Information
Hutton began his 1785 abstract by outlining the aims of his work:
The purpose of the Dissertation is to form some estimate with
regard to the time the globe of this Earth has existed, as a world
maintaining plants and animals; to reason with regard to the
changes which the earth has undergone; and to see how far an end or
termination to this system of things may be perceived, from the
consideration of that which has already come to pass.
He went on to note on page 5:
That the land on which we rest is not simple and original, but
that it is a composition, and had been formed by the operation of
second causes.
He realised that the sediments had to have become consolidated, and
he suggests that the mechanisms by which this could have happened
was through the cementation of sediment particles by cements pre-
cipitated from sea water, or by the action of heat, which caused the
unconsolidated sediments to fuse together. He argued that the sedi-
mentary rocks would have had to have been uplifted from their place
of deposition in the sea, to a point where they were on dry land above
sea level. How did he explain the second problem, that of uplift? He
invoked the same heat of fusion which he said 'might be capable of
producing an expansive force, sufficient for elevating the land, from
the bottom of the ocean, to the place it now occupies above the surface
of the sea.' This land mass, he pointed out, consisted of irregular
twisted, folded and fractured rock which had been produced by the
subterranean heat. He went on to discuss the disposition of 'veins'
which he had observed to cross-cut pre-existing rocks, and which he
considered to be the products of volcanic melting. Importantly he
identified these veins as being basaltic (they were sills and dykes in
modern terminology) and he distinguished them from modern volca-
nic lavas. Modestly Hutton contended that:
There is nothing visionary in this theory, [it] appears from its having
been rationally deduced from natural events, from things which
