Leonardo da Vinci (1452 – 1519)

1. Leonardo da Vinci (1452 – 1519) “And a little beyond the sandstone conglomerate, a tufa has been formed, where it turned towards Castel Florentino; farther on, the mud was deposited in which the shells lived, and which rose in layers according to the levels at which the turbid Arno flowed into that sea. And from time to time the bottom of the sea was raised, depositing these shells in layers, as may be seen in the cutting at ColleGonzoli, laid open by the Arno which is wearing away the base of it; in which cutting the said layers of shells are very plainly to be seen in clay of a bluish colour, and various marine objects are found there.” He calculated the sedimentation rates in the Po River of Italy and concluded it took 200,000 years to form similar rock deposits near the river.

2. Geologic Map drawn by Da Vinci in the area surrounding the river describe in the previous quote. As the river cut through the rock layers, older ones were exposed closest to the stream channel. This is similar to the Grand Canyon in the U.S., but on a much smaller scale.

3. Steno was also a Catholic cardinal in later life and is well on the way to becoming a “Saint”. To the left, Steno was the first to describe the anatomy of the shark and pointed out that objects thought to be projectiles from the sky or Moon were actually fossil sharks teeth. NielsSteensen aka Nicholas Steno (1638 – 1686) Early Father of Geology

4. Since rocks were originally deposited in horizontal layers as in the Grand Canyon and the diagram above, when rocks were found to be like the ones below, some force must have acted to fold or bend them. We say the rocks below have been “disturbed”. Notice that in the diagram above, even when rocks are deposited over an uneven surface, the layers within it are still horizontal.

5. The Grand Canyon is a good example of Original Horizontality proposed by Steno.

7. Example of the principle of Lateral Continuity proposed by Steno

8. In contrast, Sir Isaac Newton worked on the same problem but could not find consistent data beyond 1132 BC and could not estimate an accurate date for the creation. He did, however, feel the Earth would not end before 2060 AD. (?) James Ussher (1581 – 1656) Church of Ireland the night preceding Sunday, 23 October 4004 BC John Lightfoot (1602 – 1675) Church of England October 25, 3929 BC

9. Early Geologic Column by G. Arduino circa 1750

10. Abraham Gottlob Werner – famous German “Neptunist” and most influential geologist in the 1700s. Johann Gottlob Lehmann – proponent that all rocks precipitated from a world wide ocean and that rock layers should be like the layers of an onion.

11. Geologic Column proposed by Abraham Gottlob Werner Circa 1790

12. Buffon felt the 4004 BC dates were far too young and estimated the age of the Earth to be at least 75,000 years based on the cooling rate of a sphere of iron. He was forced to retract it. Georges-Louis Leclerc, Comte de Buffon (1707 – 1788)

13. James Hutton (1726 – 1797) Scottish “Father of Modern Geology” & “Deep Time” "from what has actually been, we have data for concluding with regard to that which is to happen thereafter." "The result, therefore, of our present enquiry is, that we find no vestige of a beginning,–no prospect of an end.” Theory of the Earth 1788

14. Hutton was a very active geologist and studied many areas related to geology such a farming and chemistry. He was a leading proponent of an Old Earth and of “Plutonism”. At the time, “Neptunism” was the most popular geologic theory and it put him at odds with many of the “greatest” geologists of the time. This cartoon shows Hutton chipping away at a rock face with has erosional patterns oddly similar to the profiles of some of these opponents.

15. Examples of “disconformities – one of the classifications Hutton gave to eroded surfaces with rock deposited on top of them.

16. Angular Unconformities

17. Cross-cutting relationships – one unit crosses through another. In every case, the one cutting through HAS to be younger than the one cut.

20. William 'Strata' Smith (1769 – 1839) Father of “English Geology” and “Economic” Geology First to formally propose the “Principle of Faunal Succession” and to recognize the usefulness of fossils in interpreting strata and position in engineering and mining.

21. The first Geologic Map of England and Wales by William Smith. The “Map That Changed the World” Unfortunately at the time it was not embraced due to his “low station” and was stolen and copied by someone else who sold it as their own for much less than Smith asked. Smith ended up in debtor’s prison due to it though later his contributions were duly recognized.

23. The Principle of Faunal (Fossil) Succession Smith found that organisms were arranged in the rocks in very specific ways. The lower levels contain only “primitive” invertebrate marine organisms. As we move up the layers, the fossils change and those lost are not seen again. Eventually, organisms with bones appear, fish at first. Then we see amphibians, then reptiles and finally ancient mammals. Primates and humans are only found in the upper most layers.

24. Sir Roderick Impey Murchison, (1792 - 1871) Adam Sedgwick (1785 – 1873)

25. Charles Lyell was one of the last of the great pioneering geologists. He helped confirm many of the ideas of those who went before and promoted much of Hutton’s work. He was a proponent of Uniformitarianism, an idea begun by Hutton but not by that name. Lyell went too far sometimes however in thinking if things were not happening now, they couldn’t have happened in the past. He wrote the first great geology textbook, Principles of Geology, which was the basis for most other books for decades to come. Sir Charles Lyell, (1797 – 1875)

26. The frontispiece for Lyell’s Principle of Geology

27. Standard Geologic Column Charles Lyell Circa 1833

28. Revised Standard Geologic Column Charles Lyell Circa 1872

29. John Phillips (1800 – 1874) Nephew of William Smith English geologist who, using geologic principles, sedimentation rates and faunal succession, estimated the age of the Earth to be at least 96 million years. He also helped standardize the common units of the Standard Geologic Column.

30. John Joly (1857 – 1933) Irish Geologist Joly has several distinctions: Estimated the age of the Earth (1899) using the saltiness of the oceans and seas. He estimated between 90 to 100 million years. Although his measurements were very accurate, his ideas on saltiness were not. He was one of the pioneering radiometric geologists estimating from crude measurements (1903) that Devonian rocks he measured could not be much less than 400 million years old. He was also one of the first advocates on using radiation to treat cancer.

31. Along with Alfred O. C. Nier dated the age of the Earth at 4.5 by +/- 100 my in 1950s. He was instrumental in converting the Standard Geologic Column into the Geologic Time Scale Arthur Holmes – Super Geologist (1890 - 1965) British First to date rocks radiometrically – 370 my for Devonian rock from Norway in 1911 Based on other dates he estimated the age of the Earth to at least 1.6 by 1913 Early champion of continental drift and early proponent of convection currents in 1917. One of the architects of Plate Tectonics with Harry Hess.

32. 65 my 225 my 570 my 4.5 by Geologic Time Scale Arthur Holmes and others circa 1964