headSTART logo
headSTART logo
WorldviewsDesignCellsInvestigate Further
Impact of WorldviewsDesignCell BiologyInvestigate Further

Investigate Further

Geological Column

Level: Introductory

In Brief: One man digging shallow canals in England in the early 1800s, noticed that some of the rocks contained different collections of fossilized sea shells. Sometimes one kind of rock with one community of shells, could be found lying on top of rocks with different collections of shells. He figured out which must have come first depending upon the location above or below other rocks. This was the beginning of the idea of the geological column. All the rocks which this man studied were near the surface and there was no hint of long geological ages. The idea that it took a long time to bury these organisms came later when support for evolutionary processes became more popular. Evolution, if it really happened, would require a long time.


The illustration that we see in textbooks, with millions of year ages attached, looks like well established fact, but it isn’t really. The story of how the idea was developed, tells us a lot about how this seemingly established science was first proposed and later changed. The story gives us some hints as to the confidence we can place in the textbook illustration as it now stands. What was initially proposed was the relative order [which came first and second etc.] in which communities of mostly sea dwelling creatures were entombed by sediments sinking out from fast moving water currents. Those sediments later turned to rock. [see Fossils]

Way back in the 1600s, Dutch geologist Niels Steensen (Steno) first provided the way to understand deep accumulations of rock. He pointed out that the oldest rocks must be located at the bottom of a collection of rocks and the youngest at the top. This is a particularly useful concept when we want to study sedimentary rocks. These are rocks which were initially sediments (gravel, sand or clay) that were carried along by moving water currents and later allowed to sink out where we now find them hardened and solid. Since Steno’s time, there has been no shortage of people speculating on the nature of the rock record. It was a canal digger and surveyor in England, however, who provided the first firm information with which to analyze the relationship of the various rock collections to each other.

William Smith (1769-1839) had no particular interest in geology. He was just digging canals and roads around England and Wales, especially for the purpose of transporting coal to distant parts of the country. As time went on, Mr. Smith noticed particular collections of fossils in rock layers that his excavations disturbed. Mostly the fossils were sea shells which would have lived at some time in the past in the ocean. Some identifiable collections of fossils were routinely found in layers that extended considerable distances. When he saw a similar collection of fossils some distance away, he knew it came from the same layer as the one he had previously seen. Other collections of fossils (different organisms) were found below the initial layers (or above them). Curious to see how far these fossil bearing layers extended, Mr. Smith began to plot how far down or how far away a given collection of fossils could be found.

In 1815 he shared with others a beautiful, hand-coloured map of the geological formations [distinctive fossil communities] in England and Wales. He did not observe the kind of deep collection of rocks illustrated in the textbook geological column. Instead he figured out what the logical order of deposits must have been based on local fossil beds. For example if bed C was found under bed J locally and if M was found over J, then eventually he was able to conclude that the order of deposits was MJC.

So the geological column was initially pieced together from rock units in England and Wales. The work of William Smith resulted in the figuring out of the relative order of the laying down of various fossil collections, but that was all it was. Mr. Smith himself viewed these rocks as having occurred during the flood of Noah. He reflected the prevailing view of world history at that time. It is evident nevertheless that there was nothing in these rocks which would lead Mr. Smith to conclude that they represented collections made over long geological ages.

So, the major geological formations were named for fossil collections in rocks in England and Wales. Cambrian rocks were named for an ancient word for Wales. Ordovician rocks and Silurian rocks were named for ancient Welsh tribes. Devonian rocks were found in Devon, Somerset and Cornwall, the southwest peninsula of England.  You get the idea. The name for Cretaceous rocks came from the wonderful white cliffs of Dover (southern England). All these differently named rock formations were not found lying at considerable depths above or below each other, but scattered around the country. Nevertheless, it was possible to logically figure out the order in which the sediments had sunk out of water and turned to rock.

Index fossils which were unique to a single community or rock formation, were very useful to Mr. Smith in identifying which rocks should be located below others and how far away a given collection of fossils could be found. An index fossil bears a unique marking or shape not found on any other organism. When a unique fossil was found only in some rocks but not others, Mr. Smith was able to distinguish the rocks with the unique species from other rocks that lacked it.  Index fossils are still used today to identify rocks with similar collections of creatures nearby or far away. For example, chalk layers (and their unique collections of creatures) are handy to identify Cretaceous rocks on other continents.

Even before Mr. Smith lived, there were many academic people, interested in world history, who considered the world to be very old. Eventually, based on evolutionary ideas and assumptions, the rock column was assigned ages of millions and billions of years. But it is with the use of index fossils that rocks are assigned an ancient age even if they lie on the surface and so could potentially have lived recently. For example, scientists recently have dug up dinosaur bones from a surface creek in southwest Edmonton. They say that the bones are Cretaceous and so at least 65 million years old. This age assignment comes not from their deep location now, but is based on the fact that they are dinosaur bones. Similarly rocks on the shore of Lake Superior near Thunder Bay (in Ontario) are said to be Precambrian  (possibly 2 billion years old), not on the basis of their deep location in the rocks, but on the basis of the kinds of microorganisms found there. One of those unusually shaped microbes, called Kakabekia, is however found living in soils around the world today. [see footnote]

It is nevertheless true that there are some places where deep accumulations of rock (such as the Grand Canyon) can be studied. The order of the rocks deposited in these deep cliffs seems very close to the geological column in the textbooks. So, the Geological Column represents logical conclusions about the order of fossil communities based on the presence of index fossils in the various layers. However, the process of deposition could have been fast or slow. The Biblical understanding of this situation is that the order of depositing reflects events that took place in the Flood of Noah. These events during one year resulted in certain collections of organisms being buried and entombed before others. [There are many reasons for concluding that most sedimentary rocks were deposited very quickly. See rock record.]

Footnote:  In 1954 Stanley Tyler, a geologist from the University of Wisconsin, made a field trip to northwestern Ontario in search of iron ore deposits. Something else however caught his eye. On the north shore of Lake Superior, eight km west of the tiny hamlet of Schreiber, Tyler spotted strange white concentric rings about 1 metre in diameter in the rock. Geologically this proved to be a very exciting discovery. The mining companies however could not have cared less. The interest in this find was intellectual, not economic.

The rocks which Tyler found, are called stromatolites. The name comes from a Greek word stroma meaning bed or layer. The idea is that these rocks are made up of many layers laid down in a more or less concentric pattern. The Schreiber stromatolites are made of very hard rock that aboriginals originally used for arrowheads. Later Europeans used the same rock for gunflints. Scientists now call this material chert, a kind of hard silica (glass and sand are both high in silica).

Tyler, assisted by famous palaeontologist Dr. Elso S. Barghoorn from Harvard University, made thin slices of rock and examined them under the electron microscope. These two scientists then astonished and delighted the scientific world when they announced that they had found the most ancient microorganisms known. The time at which these organisms had lived was estimated to have been possibly two billion years ago.

One fossil bacterium discovered from the Gunflint Iron Formation in chert was at Kakabeka Falls near Thunder Bay. The appearance of this microbe was very distinctive and nothing like it was known. However in 1964 a microbe that looked exactly like the fossil microbe from Kakabeka Falls was discovered living in the soil around a much used urinal in a castle at Harlech, Wales. What strange sites will scientists think to research next! This organism has been discovered alive in other parts of the world, in soils at sites high up in mountains of Alaska, Iceland, Japan and Hawaii. Scientists gave this new microbe discovery the same name as the fossil specimens: Kakabekia.

Related Terms

  • Sedimentary Rock