3. GEOLOGIC TIME. John Playfair stares into the abyss of time at Siccar Point, Scotland. AGE OF THE EARTH – 4004 BC. OR OLDER ?.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
3. GEOLOGIC TIME
John Playfair stares into the abyss of time
at Siccar Point, Scotland
AGE OF THE EARTH – 4004 BC. OR OLDER ?
James Ussher (1581-1656), Anglican Archbishop of Armaghin Northern Ireland, and Primate of All Ireland. His precise dating of the moment of the Creation as occurring at nightfall preceding Sunday, October 23, 4004 BC, is included in the margins of fundamentalist Bibles. Published posthumously in 1658, Annals of the World is an extraordinary work attempting to give an account of major events in history from 4004 BC to 1922 BC, and from then an almost year by year account up until 73 AD..
OTHER ESTIMATES OF THE AGE OF THE EARTH BASED ON THE BIBLE
The Venerable Bede (723 )3952 BC
Johannes Kepler (1596)April 27, 3977 BC
John Lightfoot (1644)3929 BC
James Ussher (1658)October 22, 4004 BC
Isaac Newton (1687)4000 BC
In 1774 Georges-Louis Leclerc, Comte de Buffon (1707-1788), concluded that the Earth was probably about 75,000 years old. His estimate was based on experiments on the cooling rate of iron. He also proposed that the planets had originated when a comet had struck the Sun. But Buffon’s most important work was in biology, published as the Histoire naturelle, générale et particulière in 36 volumes between 1749 und 1788. Hisobservations anticipated the idea of evolution. His age of the Earth was rejectedby the authorities at the Sorbonne
The importance of time
The idea of a vast expanse of time has been the major philosophical contribution of geology
Geologic change is not perceptible on human timescales
Geology began as a science during the Scottish Enlightenment in 1785 – with the recognition that Earth had a long history
THE DISCOVERY OF THE DEPTHS OF TIME - ETERNITY
The recognition of the immensity of geologic time seems to have occurred one clear day in the summer of 1788, when three people who considered themselves ‘geologists’ sailed along the Scottish coast east of Edinburgh and landed at a place called Siccar Point.
James Hutton (1726-1797) is now known as the ‘Father of Geology’, Sir James Hall of Dunglass (1761-1832), President of the Royal Society in Edinburgh, and mathematician John Playfair (1748-1819), Hutton’s close friend. There they saw steeply inclined beds of slate, covered by gently sloping red sandstone.
Sir James Hall’s sketch (1788) of the rocks at Siccar Point
In 1805 John Playfair described their experience: “The mind seemed to grow giddy by looking so far into the abyss of time.”
James Hutton stated "we find no vestige of a
beginning, no prospect of an end." The Earth might be eternal.
SICCAR POINT TODAY
James Hutton – The Father of Geology
Hutton’s book: Theory of the Earth with Proofs and Illustrations, published in 1795, was a bit of a disaster – poorly written and missing many of the illustrations (they were discovered in a printers shop in Edinburgh a few years ago).
John Playfair successfully rewrote it as Illustration of the Huttonian Theory of the Earth, published in 1802
1789 - A TIME FOR REVOLUTION
A year after Hutton, Playfair, and Hall visited Siccar Point, on July 14, 1789, the great prison in Paris, the Bastille, was attacked and torn down. The French Revolution was under way.
One of the revolutionaries was Jean Léopold Nicolas Frédéric Cuvier. He was 20 years old.
At the age of 30 he was appointed Professor at the Botanical Garden in Paris
(formerly the Royal Gardens), which then came to house the Muséumnationaled’histoireNaturelle . He was an avid collector of fossils, and an observant geologist.
For the French aristocracy, the 1789 Revolution was a catastrophe, as was the Reign of Terror of 1793-94. Cuvier survived all that as an observer, but the idea of catastrophic change was in the air.
Cuvier became a close friend of Napoleon, and convinced him to send back to Paris the natural history collections from cities and towns in the areas he conquered.
These greatly enhanced the collections already in Paris and made the Muséumd’HistoireNaturelle one of the worlds greatest museums.
The word ‘catastrophe’ is derived from the Greek and means turning things upside down. A catastrophe is defined as a sudden event with dire consequences.
Cuvier held to the idea that the Earth was about 6,000 years old, so catastrophes were required to fit in all that had happened since the planet had formed. He noted that the fossil faunas of the strata surrounding Paris, mostly molluscsand vertebrates in the marine strata, were the same from top to bottom. The retreat of the sea and subsequent flooding is often represented by thin strata or even bedding planes between the strata. He concluded that the transgressions and regressions occurred very rapidly in response to catastrophic geologic movements.
We now know that the fossiliferous rocks in the Paris Basin are a very incomplete record; most of the geologic time is represented by ‘hiatuses,’ lengthy gaps in the record represented only by thin sediments or surfaces between the major rock units. Cuvier had thought these boundaries represented very short periods of time; today we know they represent much more time than do the deposits. The misinterpretation of Cuvier’s ideas of two hundred years ago has been recently resurrected as ‘Intelligent Design.’
CATASTROPHISM REPLACED BY IMPERCEPTIBLY,SLOW GRADUAL CHANGE
Charles Lyell (1797-1875) was the first ‘modern’ geologist. He argued that the geologic process of the past were the same as those of today. Geologic change was imperceptibly slow. This idea became known by the unwieldly term
His book Principles of Geologypresnets cogent arguments that the change of climate implied by the tropical coal beds of England to its modern climate were due to changes in the distribution of land and sea.
Global climate change was the major topic of the first general book on geology
The piddling school of geology
Bless the baby what a valley he have a-made !!
Cause and Effect
Not everyone agreed with Lyell’s idea that geologic processes were very slow. Henry de la Beche’s cartoon (circa 1830) shows a little boy urinating, lampooning Charles Lyell’s idea that processes that have shaped the Earth throughout its history are the same as those acting today
1826 – 1840 Discovery of theIce Age
Even before publication of Lyell’s books, disturbing new evidence of climate change had come to light. Around the Alps, in northern Europe and in parts of the British isles there were strange landforms - U-shaped valleys, long ridges of sand, gravel and boulders, and occasional huge blocks of rock resting on the soil. These features were attributed to the Biblical Flood; the deposits were called “drift” and their age given by Lyell as “Diluvian,” the time of the deluge, that is, the Biblical flood. Some of these things were hard to explain. The boulders, for example, were thought to have been transported by icebergs in the flood waters - but then came the question: how did icebergs get into the flood waters?
Louis Agassiz (187-1873)
Giebichenstein, near Stöckse, Niedersachsen, Germany
Glenwoodville, Alberta - 1881
The Train of Erratics, Alberta
In Switzerland naturalists were discussing the similarity between the deposits of the Swiss Midlands and the materials surrounding the glaciers in the Alps. They were discovering what the farmers in the alpine valleys already knew. Glaciers were ‘living things.’ They advanced and retreated, and their deposits could be found far down the valleys they occupied.
In 1826 IgnaceVernetz proposed to a meeting of the Swiss Natural History Society that the glaciers had been much larger and covered the whole region. Word passed from one scholar to another until Louis Agassiz heard about it.
Agassiz was Professor at the Lyceum of Neuchatel, and a paleontologist who specialized in studying fossil fish. He thought the idea was ludicrous, but after a field trip into the Alps with Jean de Charpentier, one of the hypothesis’ proponents, he became convinced it might be right and spent several years gathering further evidence.
Rhone Glacier – 1913 - 2006
A glacial erratic beside a glacier, Alaska
Then, in 1840 Agassiz attended a meeting of the British Association in Glasgow, Scotland. After the meeting he traveled through Scotland with Buckland, and Roderick Murchison, a Scottish gentleman geologist. With Agassiz’s interpretation of the Scottish landscape as having a glacial origin everything suddenly made sense.
The U-shaped valleys had not been carved out by the tiny streams in them today but by moving ice; the strange longitudinal hills of detritus were glacial moraines; and those odd boulders scattered about the landscape had been transported by the glaciers. Buckland became an enthusiastic supporter of the glaciation hypothesis, and he eventually converted Lyell.
Agassiz met Professor William Buckland of Oxford University at a naturalists meeting in Freiburg-in-Breisgau on the Rhine in Germany not far from the Swiss border. Buckland, originally a catastrophist, was gradually changing his mind about how the Earth had evolved. He had been Lyell’s teacher (and had been given Henry de la Beche’s cartoon).
Agassiz invited Buckland to come with him into the Jura mountains to look at the evidence that glaciers had been there. Buckland was not convinced, but displayed an open mind. When Lyell heard about the idea of widespread glaciation he felt it was a challenge to his notion of gradual change, almost a return to catastrophism. Other British geologists also rejected the idea.
THE DISCOVERY OF PAST WARM POLAR REGIONS
Just as the idea of large ice sheets during the Earth’s recent and ancient past was becoming accepted, evidence was found that Earth had also been much warmer in the past. Adolf Erik Nordenskiöld (1832-1901) was born in Finland, but later emigrated to Sweden. He was a geologist and Arctic explorer. In 1870, in a search for the Northwest Passage, he landed on western Greenland’s Nûgssuaq(Noursoak) Peninsula (70.5° N), north of Disco Island. In the Cretaceous strata there he found a fossil flora rich in tropical plants, including the remains of breadfruit trees.
Through the 19th century a sequence of geologic strata was put in order and a relative geologic timescale developed.
Geologists believed it involved many hundreds of millions of years.
The physicist Lord kelvin argued that the Earth was about 100 million years old.
THROWING A MONKEY WRENCH INTOEXPLAINING CLIMATE CHANGE
James Dwight Dana (1813-1895) was an American mineralogist, a Professor at Yale, and, best known for his book Dana’s System of Mineralogy. He also published a Manual of Geology (1863) in which he introduced a concept that was to become both a tenet of American geology and a monkey wrench in development of any understanding of climate change — the permanence of continents and ocean basins. In contrast to Lyell’s idea that land could become ocean and vice versa, Dana believed that the continents and ocean basins had formed when the Earth solidified. The more dense rock formed the continents and the less dense rock was to form the basement of the ocean basins. His idea was that the more dense rock did not contract as much as the less dense rock, hence as the Earth cooled, the less dense rock formed basins which collected water. These different types of basement rock had remained fixed in size and position ever since.
‘CRUSTAL MOBILITY’ TO THE RESCUE
In Marburg, Germany, just before WWI, Alfred Wegener and his father in law, ValidimirKöppenplotted maps showing the distribution of the then-known climate sensitive sediments and fossils. They came to a remarkable conclusion. The Late Paleozoic glacial deposits of India, Australia, South Africa and South America could better be explained if these continents were simply fragments of a much larger southern hemisphere continent, Gondwana. Furthermore, the similarity of deposits of North America and Eurasia could be readily explained if there had been no Atlantic Ocean separating them.
THE RETURN OF CATASTROPHISM AND THE IDEAOF RAPID CHANGE
In 1969. DigbyMcLaren, a prominent Canadian geologist and Paleontologist postulated that an asteroid impact was responsible for the great extinctions near the end of the Devonian Period, about 360 million years ago.
The idea received mixed reviews from the scientific community.
However, in 1980 Walter Alvarez and his father, Luis, presented evidence that an asteroid had struck the Earth at the end of the Cretaceous period, 65 million years ago, causing the extinction of dinosaurs and many other forms of life. Skeptics that such a thing could happen had second thoughts when the fragments of the comet Shoemaker-Levy began crashing into Jupiter on July 16, 1994.The disturbances in Jupiter’s atmosphere were larger in size than planet Earth itself. It was a sobering experience for everyone who thought that catastrophes were fantasy
THE NATURE OF THE GEOLOGIC RECORD
Older sediment is eroded to make young sediment
THE GREAT EXTINCTIONS AND THEIR CAUSES
Through the 19th century –
A long and complex history without specific ages