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10 Breakthroughs in geology

TEN BREAKTHROUGHS IN GEOLOGY

Deep time 
Who: Aristotle
When: 4th century BC
the Greek philosopher recognised that the earth changes at an indiscernably slow rate, writing: “the distribution of land and sea in particular regions does not endure throughout all time” – a concept dubbed ‘deep time’.


Stratification of the earth’s crust
Who: Abraham Werner
When: 1774
As the creationist views of early geologists softened, German geologist Werner proposed a system of classification of rocks and divided them into five chronological formations.


Geomorphology
Who: Shen Kuo
When: 11th century Ad
chinese scientist shen Kuo (AD 1031–95) made observations of marine fossil shells in mountains far from the ocean, and proposed that the rocks were once on a seashore. He theorised that land formed from uplift and silt deposits, and is gradually eroded.


Continental drift 
Who: Abraham Ortelius
When: 1596
though Alfred Wegener is credited with the idea of continental drift – land splitting from an ancient single mass, a hypothesis he presented in 1912 – over three centuries earlier the flemish geographer ortelius had suggested that the Americas had once been connected to e and Asia.


The earth’s core 
Who: Richard dixon Oldham
When: 1906
oldham analysed the speed at which earthquake waves travel through the earth, and noticed that the speed drops markedly towards the centre – thence deducing the existence of a core of a different density.


Geological strata
Who: Ibn Sina (Avicenna)
When: c Ad 1027
in his Book of Healing, the great Persian polymath ibn sina described the process by which layers of rocks of different hardness – geological strata – are overlaid and eroded at varying rates.


Fossils identifying strata 
Who: William Smith
When: c 1799
Known as the ‘father of english Geology’, smith’s studies of the rock layers of england led him to propose the theory of faunal succession, stating that fossils of the same age would be found in similar rock strata across the country.


Paleomagnetism
Who: Stanley Keith Runcorn
When: 1940s and 1950s
the British geophysicist runcorn established the study of residual magnetisation in ancient rocks. His work demonstrated reversals of earth’s magnetic field, and provided evidence for continental drift.


Accurate age of the earth
Who: Clair Cameron Patterson
When: 1953
the American geochemist used lead isotopic data from the canyon Diablo meteorite to calculate the earth’s age to within 70 million years. His figure, 4.55 billion years, has remained essentially unchallenged since.


Plate tectonics
Who: John Tuzo Wilson
When: 1965
the concepts involved in explaining Wegener’s theory of continental drift had been developed and refined with the discovery of mid-ocean ridge spreading and the study of paleomagnetism, but tuzo Wilson added the final elements to complete the picture of massive moving plates.

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