Deep time

Deep time is a term introduced and applied by John McPhee to the concept of geologic time in his book Basin and Range (1981), parts of which originally appeared in the New Yorker magazine. The philosophical concept of geological time was developed in the 18th century by Scottish geologist James Hutton (1726–1797); his "system of the habitable Earth" was a deistic mechanism keeping the world eternally suitable for humans. The modern concept entails huge changes over the age of the Earth which has been determined to be, after a long and complex history of developments, around 4.55 billion years. Hutton based his view of deep time on a form of geochemistry that had developed in Scotland and Scandinavia from the 1750s onward. As mathematician John Playfair, one of Hutton's friends and colleagues in the Scottish Enlightenment, remarked upon seeing the strata of the angular unconformity at Siccar Point with Hutton and James Hall in June 1788, "the mind seemed to grow giddy by looking so far into the abyss of time". Early geologists such as Nicolas Steno (1638–1686) and Horace-Bénédict de Saussure (1740–1799) had developed ideas of geological strata forming from water through chemical processes, which Abraham Gottlob Werner (1749–1817) developed into a theory known as Neptunism, envisaging the slow crystallisation of minerals in the ancient oceans of the Earth to form rock. Hutton's innovative 1785 theory, based on Plutonism, visualised an endless cyclical process of rocks forming under the sea, being uplifted and tilted, then eroded to form new strata under the sea. In 1788 the sight of Hutton's Unconformity at Siccar Point convinced Playfair and Hall of this extremely slow cycle, and in that same year Hutton memorably wrote "we find no vestige of a beginning, no prospect of an end". Other scientists such as Georges Cuvier (1769–1832) put forward ideas of past ages, and geologists such as Adam Sedgwick (1785–1873) incorporated Werner's ideas into concepts of catastrophism; Sedgwick inspired his university student Charles Darwin to exclaim "What a capital hand is Sedgewick [sic] for drawing large cheques upon the Bank of Time!".