James Hutton

Founder of modern geology

"But if the succession of worlds is established in the system of nature, it is in vain to look for any thing higher in the origin of the earth. The result, therefore, of our present enquiry is, that we find no vestige of a beginning, no prospect of an end."

Hutton, James (1788) Theory of the earth; or an investigation of the laws observable in the composition, dissolution and restoration of land upon the globe. (From. the Trans., Roy. soc. of Edinb.).

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The granite at Glen Tilt lies between other rocks. Hutton understood the granite had to have been younger and molten to intrude through the existing rock, supporting the theory of 'plutonism'. At that time there were two competing theories for the formation of granite and basalt. The plutonists believed igneous rocks came from deep within the earth and crystallised from hot molten magma. The neptunists believed all rocks formed from crystallisation in a vast ocean, with only new volcanic rocks formed by melting. The plutonist theory was eventually accepted as correct.

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Hutton's Unconformity

An unconformity is a boundary between rocks. The Dalradian schists formed about 540 million years ago and are the oldest rocks on Arran. The Carboniferous sandstones are much younger at around 350 million years old. Hutton observed these much younger rocks above the ancient schists and estimated they must have taken millions of years to form.  At the time, the Earth was believed to be 6,000 years old. Hutton showed that the Earth must be much older.

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Explore for yourself in this 3D model. Click on image (external link)