Geologic Column

originally Message 371Hi Peg, You're welcome. That depends on how you look at it. The "column" is complete in every location - it has all the layers for that location. If we are looking for one location that has all the layers, then the "column" is the earth. Each new layer wraps around the previous layer, taking the shape of the previous layer/s as its base, and builds onto it.It also depends on what you call a layer. There is a layer called the iridium layer that covers a large proportion of the earth, and is the evidence of the meteor strike that hit the Yucatan Peninsula 65 million years ago - it has a distinctive level of iridium that is characteristic of meteors, hence it can be identified. This layer does not exist where it has been eroded away (such as where Tiktaalik was discovered), but it covers many different formations that are discontinuous layers, and it in turn is covered by many discontinuous layers. There are similar layers that contain volcanic ash, which covers a much wider area than lava, and in some cases can be found world wide. This is where the fun (for geologists) comes in. Some layers are necessarily local - volcanic lava flows do not cover the earth, but every one of them covers part of the earth, over older formations, so you may have several different sources providing material that cover different parts of other layers. Rather obviously you are not going to have lava flows from Oahu island in Connecticut, nor are you likely to find a sedimentary deposit from the Connecticut river on one of the islands in Hawaii.What you are going to have are groups of layers of the same approximate age, with different members of the groups in different places. The rock layer that exists now on the surface in Oahu and the Connecticut valley both represent the current age. Likewise the layers that existed on the surface 100 or 1000 or whatever years ago represent the age of the earth at that time. Note that in some areas the surface is eroding away to expose older layers, and in some areas it is building up new layers, and some new building layers are formed from old eroded layers, formed into new layers.Thus if you arrange the layers all over the earth in a chronological by depth order you will have a number of discontinuous layers included in different areas, and you will have something like: Where any member of the A group will be over any member of the B group that occur in the same location.You may or may not find areas where a1 and a2 both occur to see which is over the other, but you can still build up a relative chronology in every area by the layers.Geologists give groups of layers of the same relative age names according to their age, a system of relative dating of formations that is as old as the law of superposition.Is there one location that has a layer that represents every known geological age? Probably not, but that is not necessary for the "geological column" to be a valid concept of relative age.See Geologic time scale - Wikipedia
Geologic time scale(Redirected from Geological column)

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The geologic time scale is a chronologic schema (or idealized model) relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The table of geologic time spans presented here agrees with the dates and nomenclature proposed by the International Commission on Stratigraphy, and uses the standard color codes of the United States Geological Survey.

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Evidence from radiometric dating indicates that the Earth is about 4.570 billion years old. The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually delimited by major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the Cretaceous—Tertiary extinction event, which marked the demise of the dinosaurs and of many marine species. Older periods which predate the reliable fossil record are defined by absolute age.

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Each era on the scale is separated from the next by a major event or change.

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Each era is represented by a group of layers, all of which are above or below the group of layers that make up the other eras. Geologists don't expect the "geological column" to exist in its entirety in any one area, but they do expect the overall pattern of superposition of newer layers over older layers to occur in all locations, and use the term "geological column" to refer to this general pattern of superposition, rather than to a specific column.Is there any place on earth where you can link a path between layers in direct absolute chronological order representing every (known) era/age of the earth? Yes.For further reference see PRATT CD101 (Talk Origins)

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1. The existence of the entire column at one spot is irrelevant. All of the parts of the geological column exist in many places, and there is more than enough overlap that the full column can be reconstructed from those parts.

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Breaks in the geological column at any spot are entirely consistent with an old earth history. The column is deposited only in sedimentary environments, where conditions favor the accumulation of sediments. Climatic and geological changes over time would be expected to change areas back and forth between sedimentary and erosional environments.

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2. There are several places around the world where strata from all geological eras do exist at a single spot -- for example, the Bonaparte Basin of Australia (Trendall et al. 1990, 382, 396) and the Williston Basin of North Dakota (Morton 2001).

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Does that help?Enjoy.

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Hi Peg, sorry for the delay in reply, but I wanted to give this some more detail. As others have noted, it is very consistent, and more to the point, in those places where it does not appear to be consistent, there are reasons for in the inconsistency. Thus a look in one small area may display an anomaly, however when you look at the larger picture it becomes clear. The overthrust mentioned is a clear demonstration of this. The layers that are present in that location would be in order, provided that they had not been disturbed later by some other geological process (such as an overthrust). Note that some layers could be missing whole eons due to erosion, so there could be gaps in different locations.The layers would not be out of sequence (ACB instead of ABC), and this can be further checked by that other part of the superposition law: that the first formed layer controls the shape of the bottom of the next layer: one can look at the interface and determine which is the "first formed" side and which is the "second fit" side. Thus if you did find an area with ACB layers and you looked at the interface between B and C you would see that B conformed to C rather than the other way, thus these layers had been inverted before A was added. The ages assigned to the rock layers are very reliable and consistent (see previous post). The ages assigned to the different life-forms found in the layers are the ages of the layers.When we look at the areas where fossils are discovered, they are of interest to the paleontologists because the upper layers have eroded away, and they don't have to dig as far down to uncover the ages in question. For example, where Tiktaalik was discovered:BBC NEWS | Science/Nature | Arctic fossils mark move to land

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Before these finds, palaeontologists knew that lobe-finned fishes evolved into land-living creatures during the Devonian Period.

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But fossil records showed a gap between Panderichthys, a fish that lived about 385 million years ago which shows early signs of evolving land-friendly features, and Acanthostega, the earliest known tetrapod (four-limbed animals) dating from about 365 million years ago.

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In 1999, palaeontologists Professor Neil Shubin, from the University of Chicago, and Professor Edward Daeschler, from the Academy of Natural Sciences in Philadelphia, set out to explore the Canadian Arctic in an attempt to find the "missing link" that would explain the transition from water to land.

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Why the Canadian arctic?Tiktaalik roseae: The Search for Tiktaalik

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We look to geological maps of the world to help us find areas with rocks of the right type and the right age which have not been explored yet.

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We happen to know that lobe-finned fish and the first tetrapods lived in freshwater streams because of the sediments we find them in. So we're looking for freshwater deposits, not marine. We also have pinpointed a gap in the fossil record 380-363 million years ago which is likely to produce our transitional form. That time period is known as the Middle Devonian. ...

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A geological map of North America shows which rocks are at the surface. Each color indicates a different age of rocks and there are over 900 different groups of rock mapped within those ages. The Devonian rocks we're looking for are one of the shades of blue.

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Image courtesy of the Geological Society of America and the United States Geological Survey.

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(image used above is from Geosciences and Environmental Change Science Center | U.S. Geological Survey)The big white area at the top is Greenland. The find was on Ellesmere Island which abuts Greenland at the top of the map. It is shown in green here:
Erreur HTTP 404 - Non trouv | HTTP Error 404 - Not Found - All Versions We find very few organisms that span eons of time, and those that do, still show changes - the Coelacanths for instance, where modern ones are a different genus, live in a different ecology and are much larger than any of the prehistoric ones from the age of dinosaurs. There are also few organisms that span large geological areas. Some organisms are more universal in geological area covered, while their species are also closely related to the age of the rock layer/s they are found in. For instance foraminifera are used as an index fossil:Biostratigraphy - Wikipedia

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Index fossils (also known as guide fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). They work on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil. If the species concerned were short-lived (in geological terms, lasting a few hundred thousand years), then it is certain that the sediments in question were deposited within that narrow time period. The shorter the lifespan of a species, the more precisely different sediments can be correlated, and so rapidly evolving types of fossils are particularly valuable. The best index fossils are common, easy-to-identify at species level, and have a broad distributionotherwise the likelihood of finding and recognizing one in the two sediments is low.

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Foramins are used as an index fossil to gauge the of the age of the rock until radiometric data can confirm it, because they are in so many layers of (marine) sedimentary rock, but each species is only found in a narrow age band.http://www.gomr.mms.gov/homepg/whatsnew/papers/biochart.pdfThis chart lists the geological time on the left, the various ages and eons under the CHRONOSTRATIGRAPHY heading and the different foramin species under the BIOSTRATIGRAPHY heading. If you search the chart for Globorotalia tosaensis tosaensis, for example, you will find that it is only listed during one of these age layers in the lower Pleistocene, or Calabrian stage, and thus finding this species of foram would indicate the rock was from this period.Curiously, not only do we have confirmation of the relative ages with radiometric ages for the rocks that foramins have been found in, we also have the full evolutionary picture of the diversity and development of the different species: Geology Dept article 3

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Drs. Tony Arnold (Ph.D., Harvard) and Bill Parker (Ph.D., Chicago) are the developers of what reportedly is the largest, most complete set of data ever compiled on the evolutionary history of an organism. The two scientists have painstakingly pieced together a virtually unbroken fossil record that shows in stunning detail how a single-celled marine organism has evolved during the past 66 million years. Apparently, it's the only fossil record known to science that has no obvious gaps -- no "missing links."

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"It's all here -- a complete record," says Arnold. "There are other good examples, but this is by far the best. We're seeing the whole picture of how this organism has changed throughout most of its existence on Earth."

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They have been able to show the evolution of almost every species of foram from generation to generation, thus validating the relative ages of the layers and the sequence of age of those layers.Not only do the layers correlate with radiometric ages, but they correlate with the changes over time of the species found in them.Enjoy.

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Hi Peg, Sir Charles Lyell was a contemporary of Darwin and a leading proponent of uniformitarianism:Charles Lyell - Wikipedia

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Principles of Geology, Lyell's first book, was also his most famous, most influential, and most important. First published in three volumes in 1830-33, it established Lyell's credentials as an important geological theorist and propounded the doctrine of uniformitarianism.[6] It was a work of synthesis, backed by his own personal observations on his travels.

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The central argument in Principles was that the present is the key to the past. Geological remains from the distant past can, and should, be explained by reference to geological processes now in operation and thus directly observable. Lyell's interpretation of geologic change as the steady accumulation of minute changes over enormously long spans of time was a powerful influence on the young Charles Darwin. ...

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... He was, along with the earlier John Playfair, the major advocate of James Hutton's idea of uniformitarianism, that the earth was shaped entirely by slow-moving forces still in operation today, acting over a very long period of time. This was in contrast to catastrophism, a geologic idea of abrupt changes due to unknown forces, which had been adapted in England to support belief in Noah's flood.

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If anything Lyell may have overemphasized the gradual processes observed in geology in so many areas, however I am sure he was aware of certain abrupt processes, such as volcanic lava and ash deposition, in addition to what is mentioned by Vacate and Percy.Certainly, when we look at the layers of index fossils, such as the foraminifera, the gradual deposition of sediments makes sense because the organisms are different in the different layers, and in some cases can be observed to change in single layer groups. There have been several advances in geology that have affected the way the rocks and layers are regarded, with Plate Tectonics being the most radical change in thinking, and with radiometric dating operating as a validating check on the relative ages determined by superposition, but by and large the principles are still valid, albeit modified by modern thinking (just as evolution is modified by modern thinking from Darwin's formulations).History of geology - Wikipedia

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The history of geology is concerned with the development of the natural science of geology. Geology is the scientific study of the origin, history, and structure of the Earth. [1] Throughout the ages geology provides essential theories and data that shape how society conceptualizes the Earth.
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In recent years, geology has continued its tradition as the study of the character and origin of the Earth, its surface features and internal structure. What changed in the later 20th century is the perspective of geological study. Geology was now studied using a more integrative approach, considering the Earth in a broader context encompassing the atmosphere, biosphere and hydrosphere.[52] Satellites located in space that take wide scope photographs of the Earth provide such a perspective. In 1972, The Landsat Program, a series of satellite missions jointly managed by NASA and the U.S. Geological Survey, began supplying satellite images that can be geologically analyzed. These images can be used to map major geological units, recognize and correlate rock types for vast regions and track the movements of Plate Tectonics. A few applications of this data include the ability to produce geologically detailed maps, locate sources of natural energy and predict possible natural disasters caused by plate shifts.[53]

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So yes, I would say that the field has changed since Lyell's book, and that it has grown more complex, building on the earlier knowledge and theories and how they explain all the evidence. You can probably do significantly valid geology while knowing very little about evolution. Evolution helps to present some order to some layers via index fossils, but it is not necessary for the understanding of plate tectonics, uplift, superposition, etc.Geology involves understanding the record of the natural history of the planet, and just as written history records events, so too does the geological record record the history of past events, including floods, volcanoes, earthquakes and the long durations of seas. This would be so even if no organisms formed fossils.That certain organisms under certain conditions form fossils means that their actual individual existences in the past are recorded in the natural history of the earth. This record is not evolution, nor is it part of the theory of evolution, it is the record of what actually lived, and of what happened (floods, earthquakes, volcanoes, meteors, etc) to life in the past, whether evolution is a valid theory or not.Life occurs in the present, so it is always acting on the surface, and what is left behind, to be covered by sediments and volcanic ash and the like, are small bits and pieces of the life that was occurring at the time those sediments and ash layers formed.For the theory of evolution to be complete, in the sense of explaining all the known evidence, it needs to be able to explain not just what we see living around us today, but what we know of past life, from the geological record (climate and ecosystem), from the paleontological record (fossils), from the anthropological record (paintings and artifacts), as well as from the historical record (descriptions of dodos, etc, that are now extinct).Understanding geology is essential to understanding that part of evolution that deals with ancient life, however it is relatively irrelevant to the continued process of life in the world today, acting as the canvas upon which the picture of modern life is drawn. Shouldn't all knowledge tie together into a unified whole? Astronomy tells us about stars and planets, physics tells us how they form and thus how the earth formed, chemistry tells us how molecules act and biology tells us about how life behaves.Enjoy.

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Hi Mr Jack Excellent distinction. You can find the entire book on-line at:
ESP Digital Books: Principles of Geology, Vols 1-3 Chapters 18 to 26 are devoted to volcanoes and earthquakes.Enjoy.

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Hi again, Mr Jack It's the 1830 edition.Lyell, Charles 1830. Principles of Geology, Vols 1-3. London: John MurrayCheck out other publications available from this source
ESP What's New Wright, Sewall. 1931. Evolution in Mendelian populations. Genetics, 16:97-159.Dobzhansky, Th. and Queal, M. L. 1938. Genetics of Natural Populations. I. Chromosome Variation in Populations of Drosophila Pseudoobscura Inhabiting Isolated Mountain Ranges Genetics, 23: 239-251.Haldane, J. B. S. 1934. A Mathematical Theory of Natural and Artificial Selection Part X. Some Theorems on Artificial Selection Genetics, 19: 412-429.Some pretty good stuff and original sources for a lot of older works not normally on line.But this is getting off topic. Might be a good Links and Information item.Enjoy.

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And the fossils fit into the temporal geological matrix, closely associated with other fossils that are nearby in the matrix, with ancestral fossils nearby geologically but in older rocks, while descendant fossils are nearby geologically but in newer rocks. Similar habitats in different parts of the world often have different fossils, just as we see in the distribution of species in the world world today, and this too ties in to their position in the temporal geological matrix: you don't find fossils without nearby ancestors or descendants in earlier and later rocks.This matchup in time and space was discovered by both Darwin and Wallace, Darwin going on to write his book on evolution, and Wallace going on to concentrate on Biogeography, as I noted in the Alfred Russel Wallace and Biogeography thread, Message 1:

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On the Law Which Has Regulated the Introduction of New Species

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This is the paper where Wallace first published his "Sarawak Law" that he developed from his pursuit of biogeographical and geological relationships:

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10. The following law may be deduced from these facts:--Every species has come into existence coincident both in space and time with a pre-existing closely allied species.

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There you have the temporal geological matrix spelled out in 1855. Wallace is known as the father of biogeograpy.I can recommend David Quammen's book, The Song of the Dodo, which can be downloaded as an e-book or read on-line HERE: it is a very readable book that doesn't require a lot of scientific knowledge to understand.EnjoyEdited by RAZD, : .