Nicolaus stenos three principles used in relative dating

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Geologic Time : The science of Geology didn't take shape until the discovery of geologic time deep time. Nevertheless, by Ussher's time, ificant steps had been taken: 15th and 16th century astronomers had shown that actual observations of nature could yield important new information not found in revered ancient texts.

Nicholas Steno : Danish Critically examined the current belief among intellectuals that fossils were not the remains of organisms but, rather, "sports of nature" whose resemblance to living things was coincidental. Looking at "tongue stones" which suspiciously resembled sharks' teeth, he noted that they not only looked exactly like sharks' teeth, but that he could even say what species of shark and what part of the mouth. Steno concluded that fossils were, indeed, the remains of organisms. But this led to a problem: Fossils are found in rocks. What was a shark tooth doing inside a rock?

This led Steno to study how the rocks which we today recognize as sedimentary formed. He recognized them to be composed of lithified remains of sediment deposited in layers or strata and proposed a set of several principles of stratigraphy by which one could distinguish younger and older sediments. His were published in De solido intra solidum naturaliter contento dissertationis prodromus Preliminary discourse to a dissertation on a solid body naturally contained within a solidmercifully referred to simply as Prodromus in The two most ificant principles are: Original horizontality.

Sediments originally deposited in horizontal layers Superposition. In undisturbed strata, older layers lie beneath younger ones. Using these, it began to be possible to say what order the separate rock layers had formed in, provided they could be seen in association. More importantly, Steno was Nicolaus stenos three principles used in relative dating first to grasp that: Rocks could be formed from fragments of preexisting rocks that had been transported as sediments different rocks formed at different times.

Nicolaus stenos three principles used in relative dating

Of course, Steno thought that all of this deposition had occurred during the 40 days and nights of Noah's flood. More Rock types : Note that by the 18th century, natural historians recognized that different rocks formed as a result of different processes. Today, we recognize three basic rock types.

Nicolaus stenos three principles used in relative dating

Although the early geologists knew them by different names, today they are called: Igneous : Rock that solidify from molten material. Sedimentary : Rock that are formed from the transported remains of pre-existing rocks. Metamorphic : Rocks that have been chemically altered in a solid state by heat or pressure. More Uniformitarianism : Prologue: Remember, Steno, a traditionalist, still thought that all of this deposition took place during the flood.

In the next stage of the discovery of geologic time, natural historians took up the question of whether the Earth has a long or short history. Catastrophism - maintains that the rocks were deposited in a series of unusual upheavals. This was consistent with the story of the Flood and even after naturalistsbegan to speculate that Noah's Flood may have been only the last in a long sequence of catastrophic changes, remained by default the prevalent mind set. During the 18th century, the naturalists began to question catastrophism. James Hutton made two ificant breakthroughs: He observed that in the modern world, sediments Nicolaus stenos three principles used in relative dating still being deposited in separate layers by separate depositional events, even without a world-wide deluge.

He added two new and powerful principles of stratigraphy to Steno's: Cross-cutting relations. If one structure cuts across another, then the one that is being cut must be oldest. If eroded chunks of one material are incorporated within another, then the eroded material must be older. Hutton had his epiphany at Siccar Point. Which rocks are younger, the ones above or below? Proposed " Uniformitarianism " in his paper The Theory of the Earth Simply paraphrased, uniformitarianism holds that "The present is the key to the past.

This was a momentous and liberating idea because it meant that geologists could reconstruct the history of the Earth by observing processes in the modern world.

Nicolaus stenos three principles used in relative dating

They didn't have to invoke catastrophes in which the normal rules don't apply. Alas Hutton was a poor writer or popularizer, so his ideal got little attention until Charles Lyell: Intellectual successor to James Hutton. Published Principles of Geology three-volume set, The first geology textbook popularized uniformitarianism.

Note: Although modern textbooks treat uniformitarianism as something unambiguusly goodit has it's downsides: The early uniformiatrians went far beyond the philosophy stated above. They also maintained that all geologic processes happened at Nicolaus stenos three principles used in relative dating same rate in the past as today, and that time was eternal or maybe cyclical.

Hutton claimed that the Earth had, "no vestage of a beginning and no prospect of an end. Probable killer of the giant dinosaurs, for example. The biggest revelation was simply that the Earth had to be millions, not thousands of years old. Scroll to the bottom of this link for and example. More Relative Dating : Thus the notion of Geological time was born. Now the problem was how to measure it.

There are now two complimentary approaches: Relative dating : In which the order of the origin of various rock units is determined. Absolute or numerical dating : In which an acutal numerical chronologic age is established for rocks. More During the 19th century, however, geologists could only establish the relative ages of rock units. The means to do so had already been provided by Steno and Hutton, but only provided rocks could be seen in direct association. Once again, the study of fossils provided the stimulus for a major innovation: Faunal succession : Our understanding of fossils has a varied history: In classical antiquity, scholars knew of and were interested in the Nicolaus stenos three principles used in relative dating of ancient animals.

Roman Emperor Augustus publicly displayed ancient arms and armor plus the bones of "giants" and other mythical creatures at his estate in Capri. During the Middle Ages and Renaissance, learned people considered fossils to be "sports of nature" - mineral assembleages that coincidentally seemed to resemble living things. In ProdromusSteno argued that fossils are the remains of organisms, using fossil shark teeth as example. In William Smitha British civil engineer, added a fourth principle: Faunal successionnoting that different groups of fossil organisms were preserved in different rock units.

By this means it became possible to say that one rock was the same age as another rock halfway around the world. However, you have to use the right fossils: Index fossils : Fossils of organisms that existed for short perios of geologic time but were geographically widespread.

Example: Ammonites, Shelled cephalopods that evolved quickly so each species lasted only a few million years, but whose remains were distributed worldwide in many environments.

Nicolaus stenos three principles used in relative dating

Facies fossils : Fossils of organisms that endured for long periods of geologic time but were linked to a specific environment. Example: Lingulaa brachiopod living only in lagoonal mud-flats that has changed very little in the last million years. Modern left and ancient right examples of the brachiopod Lingula.

Of course microscopic index fossils can be superabundant, even in small rock Nicolaus stenos three principles used in relative dating, so they are particularly useful. Link to it in simplified form or in its full glory. It's major features: An internested heirarchy of larger and smaller time units. From most to least inclusive: Eon Era Period Epoch Time units had descriptive names, usually based on: The localities at which characteristic rocks were exposed E.

Jurassic for Jura Mts. Characteristic rock types E. Cretaceous for "creta" - Latin for Chalk Descriptions of fossil life found in them E. Eocene - "Dawn of the recent". But note: Geologists may have figured out that a Triassic rock were older than a Cretaceous rock, but they didn't know how old either rock was in years. To be an educated person, you must memorize the following from the simple version of the Geological Time scale. All eon names and their correct sequence.

All era, and period names of the Phanerozoic Eon and their correct sequence. The absolute ages of the beginnings of each of the eras of the Phanerozoic Eon. This WILL be on the exam.

Nicolaus stenos three principles used in relative dating

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The principle of superposition of rock strata