Geological Time

Geological Time : 

Geological Time

Age of the Earth (1): Eternity : 

Age of the Earth (1): Eternity Aristotle (384-322 BC) In classical philosophy the Earth was eternal, so Age of the Earth irrelevant © NASA

Age of the Earth (2): The Bible : 

Age of the Earth (2): The Bible 4004 BC In 1654 Bishop Ussher calculated that the Earth was created in 4004 BC He got this figure using evidence from the Bible and other Middle Eastern literature The date became so popular that it was printed with the Book of Genesis Bishop Ussher (1581-1656) en.wikipedia.org/wiki/Image:Ussher.jpg

Age of the Earth (3): Experiments : 

Age of the Earth (3): Experiments Comte de Buffon (1707-1788) In 1760, Buffon measured the cooling time of red-hot iron balls of different sizes He scaled up to the size of the Earth (75,000 years to cool) http://en.wikipedia.org/wiki/Image: Buffon_1707-1788.jpg One of Buffon’s iron balls

Age of the Earth (4): The Sun : 

Age of the Earth (4): The Sun http://en.wikipedia.org/wiki/Image: Hermann_von_Helmholtz.jpg Hermann von Helmholtz (1821-1894) In 1858, calculated the time it would take for the sun to condense to present diameter from gas nebula (around 20 million years)

Age of the Earth (5): More Physics : 

Age of the Earth (5): More Physics http://en.wikipedia.org/wiki/Image:Lord_ Kelvin_photograph.jpg Lord Kelvin (1824-1907) In 1862, Lord Kelvin assumed that Earth originally had a temperature of 7000°F Knew geothermal gradient (1°F/50 ft) Calculated cooling age (20 million years) Geothermal gradient

Age of the Earth (6): Geology : 

Age of the Earth (6): Geology Charles Lyell (1797-1875) Sediment accumulates at the same rate today as in the past so Earth must be really ancient to account for geological record (hundreds of millions of years) http://en.wikipedia.org/wiki/Image:Charles_Lyell.jpg http://en.wikipedia.org/wiki/Image:Colorado_River_edit.jpg

Age of the Earth (7): Evolution : 

Age of the Earth (7): Evolution Lord Kelvin’s “views on the recent age of the world have been for some time one of my sorest troubles” (Darwin to Wallace) In 1869, Thomson argued that there was not enough time for Darwin’s evolution by natural selection http://en.wikipedia.org/wiki/Image: Lord_Kelvin_photograph.jpg Charles Darwin Lord Kelvin http://en.wikipedia.org/wiki/Image: Darwin aged 54.jpg

Age of the Earth (8): Sea Salt : 

Age of the Earth (8): Sea Salt In 1899, John Joly calculated the Earth’s age using the saltiness of the ocean (80-150 million years) How much salt was in the Ocean? How much did rivers add each year? Obituary Notices of F.R.S., 1, 260 (1933) John Joly (1857-1933) http://www.bigfoto.com/miscellaneous/photos-16/index.htm salt crystals

Age of the Earth (9): Assumptions : 

Age of the Earth (9): Assumptions All these estimates were based on assumptions that couldn’t be proven

Geological History (1): Strata : 

Geological History (1): Strata Nicolas Steno (1638-1686) http://en.wikipedia.org/wiki/Nicolas_Steno Oldest strata Youngest strata © Howard Falcon-Lang

Geological History (2): Neptunism : 

Geological History (2): Neptunism Abraham Werner (1749-1817) http://en.wikipedia.org/wiki/Image:Abraham_ Gottlob_Werner.jpg Werner argued all rocks had been deposited in a worldwide ocean (think Noah’s Flood) Geologists could figure out the order in which rocks formed Divided geological record into four main divisions © Howard Falcon-Lang Granite

Geological History (3): Gaps : 

Geological History (3): Gaps Hutton’s unconformity showed that there were big gaps in the geological record James Hutton (1726-1797) Copyright © Marli Miller, University of Oregon http://upload.wikimedia.org/wikipedia/ commons/c/c6/James_Hutton.jpg Siccar Point

Geological History (4): Maps : 

Geological History (4): Maps William Smith (1769-1839) http://en.wikipedia.org/wiki/Image: William_Smith.g.jpg The Map that changed the World Some of Smith’s fossils

Geological History (5): Fossils : 

Geological History (5): Fossils Cuvier Cuvier showed that some animals had gone extinct Lyell used the proportion of living fossils to divide up geological time Older rocks contained more extinct types than younger rocks Charles Lyell (1797-1875) Georges Cuvier (1769-1832)

Geological History (6): Stratigraphy : 

Geological History (6): Stratigraphy A tug-of-war as rocks got sorted into geological periods in the new science of stratigraphy commons.wikimedia.org/wiki/Image :Adam_Sedgwick.jpg en.wikipedia.org/wiki/Image:Roderick _Murchison.jpg Murchison Sedgewick

Geological History (7): Periods : 

Geological History (7): Periods Carboniferous Cambrian Ordovician Silurian Devonian Permian Triassic Jurassic Cretaceous Tertiary Quaternary

Geological History (8): The Column : 

Geological History (8): The Column Geological Time: Eons, Eras, Periods and Epochs

Geological History (9): Example : 

Geological History (9): Example Impact http://en.wikipedia.org/wiki/Image:KT_boundary_054.jpg http://en.wikipedia.org/wiki/Image:Impact _event.jpg en.wikipedia.org/wikiImage:Palais_de_la_Decouvert e_Tyrannosaurus_rex_p1050042.jpg en.wikipedia.org/wiki/Image:Tyrannosaurus_BW.jpg Extinction Cretaceous Paleogene

Radiometric dating (1): Discovery : 

Radiometric dating (1): Discovery Henri Becquerel (1852-1908) In 1896, Discovery of radioactivity paved the way for the precise dating of events in the geological record

Radiometric dating (2): Decay : 

Radiometric dating (2): Decay Radioactive ‘parent isotopes’ spontaneously emit protons and neutrons and decay into ‘daughter isotopes’ E.g., Uranium-238 decays into Lead-206

Radiometric dating (3): Half life : 

Radiometric dating (3): Half life The rate of decay from parent to daughter isotope depends on its half life. The half life is the amount of time needed for half the parent isotope to decay to daughter isotope Half life: 0 Half life: 1 Half life: 2 Linear Exponential

Radiometric dating (4): Clocks : 

Radiometric dating (4): Clocks Different radioactive isotopes have different half lives Isotopes with long half lives are useful for dating old rocks. It is important to use the right tool for the right job Decay series Half life 40K to 40Ar 1250 Ma 147Sm to 143Nd 1060 Ma 235U to 207Pb 704 Ma 238U to 206Pb 4468 Ma 14C to 14N 5370 years Geological timescales Archaeology

Radiometric dating (5): Pioneers : 

Radiometric dating (5): Pioneers Arthur Holmes (1890-1965) Ernest Rutherford (1871-1937) Rutherford figured out a technique to date the age of rocks in 1904 Holmes developed this kind of ‘radiometric dating’ still further. In 1913 Holmes dated some rocks from Ceylon to 1600 million years

Radiometric dating (6): Oldest Rock : 

Radiometric dating (6): Oldest Rock Oldest rocks on Earth are the Acasta Gniess of northern Canada 4030 million years old © NASA Acasta Gneiss Zircon mineral

Radiometric dating (7): Oldest Grain : 

Radiometric dating (7): Oldest Grain 4404 Ma zircon grain © NASA Ancient mineral grain found at Jack Hills, Australia Mineral grain eroded from first crust and then deposited in a new rock Dates the Earth’s first crust to around 4404 million years

Radiometric dating (8): Meteorites : 

Radiometric dating (8): Meteorites Radiometric age of meteorites date the formation of the Solar System and Earth (4550 million years old) Crab Nebula Canyon Diablo meteorite

Radiometric Dating (9): History : 

Radiometric Dating (9): History dinosaurs humans first life origin of Earth © World Health Org. © NASA first complex cells

Geological Time : 

Geological Time © NASA