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Answers to Earth Science Questions
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  1. Why are there stone-age cultures in very recent history?


    Thomas H. Faller:

    This [set of questions] is a very mixed bunch, and is apparently an artificial category. One question is from anthropology, and is akin to the "why are there still apes?" question. The others belong in geology, but apparently the author thought that category was going badly enough. The last has nothing to do with evolution, it is apparently presented with the idea that if we can't explain the Ice Age(s), they must be Created. Ho hum

    If human tribes do not have the resources for agriculture, mining, or livestock, why should we expect them to develop farther than the hunter-gatherer culture? Through most of history, most of the world lacked a suitable range of grain crops, of draft animals, of workable metals and herd animals for "civilization" to advance.

    The question for creationists is if all were created, why were equal resources, animals and minerals not distributed to all parts of the globe?


    Floyd:

    "Stone Age" is a short hand term that archaeologists use to describe societies that make and use stone tools, do not refine metals or use metal tools, and generally do not practice irrigation agriculture. The term has no absolute chronological meaning; its actual meaning varies from society to society. The "stone age" of Europe lasted longer than the stone age of northern Africa, and the stone age of North America lasted longer than the stone age of Europe. The term simply refers to the period of time, however long that period lasted, prior to the use of metal tools.

    The short answer to this question is that this lifestyle is appropriate for and well-suited to some environments. In the deep rainforests, such as the Ituri forest of Congo, mining operations are practically impossible, so people who live there have little or no access to metal ores, and so can not make metal tools without chopping down the entire forest to start mining. Since the people who live there eat the plants and animals that live in the forest, chopping down the forest would cut off their food supply, which would be suicide. Given the choice between (a) committing suicide just to get metal tools and (b) sticking with stone tools and eating well, people are smart enough to choose option (b).

    This question, like many others, is predicated on a misunderstanding of the way evolution works. Evolution works by making organisms well adapted to their environments. It does not work as a mechanism of unilinear "progress" towards some ultimate goal. The question is inspired by an unquestioned presumption that evolution is somehow leading all cultures, and indeed all life towards becoming Europeans and Americans. This assumption has been abandoned in anthropology for decades, and in biology for centuries. So the intent of the question is misdirected, since it is a criticism of something that is not done, and has not been done in the lifetimes of most anthropologists and biologists.



  2. Why are there fossilized upright trees in coal?


    Thomas H. Faller:

    Gee, this might be a hard one if there were fossilized upright trees in coal. I can see Ed's fossilized man contentedly leaning against one... There are fossilized stumps of trees in coal, at all angles, indicating they were dead and slowly buried by further deposits that formed the coal seam. The strata around the stumps demonstrate this eaily. Fossil trees in general are either found in situ in low energy environments, or as downed and transported remains in high energy environments.

    The question for creationists is why we don't see fossilized upright trees in coal, fossilized upright trees in offshore limestones, fossilized upright trees in any energetic environment, like beside streams, overlooking oceans, in deserts, or in mountains.


    Floyd:

    The trees grew before the peat solidified into a coal seam, but perhaps after that peat paleosol had been covered with another soil layer. As the peat solidified and turned to coal, the tree roots solidified along with it, often retaining their shape to such a degree that experts can recognise the species of tree. There is no big mystery in this process; it can be seen happening today in parts of Canada and Ireland, and I'm sure elsewhere where peat is forming.

    The underlying problem with this question is the assumption that all layers of sediment form at a constant rate. If we see, for example, 10 meters of sedimentary strata, and we determine that they developed over the course of 1 million years, we have an average rate of accumulation of 1 million years per meter, or 10,000 years per centimeter. However, as anyone who has ever lived near a hillside knows, a centimeter of sediment can be deposited in a single rainstorm. Extrapolating the rate at which a centimeter of sediment forms on the basis of the average rate at which ten meters of sediment formed is simply not reasonable. An El Niņo year in the western US can easily cause ten large storms to occur in a single year, and if each storm causes a centimeter of erosion to be deposited at the base of a tree, a naive extrapolation from the average rate of accumulation might mistake that one year for one hundred thousand years. This is why actual geologists do not use naive extrapolation from average rates to individual depositional events.

    The problem is analogous to driving from Seattle to New York. The distance is 2850 miles. If I drive at 50 miles an hour for eight hours a day, it will take me one week to make this trip (7.125 driving days). However, if one were to use the naive extrapolation technique that is evident in the polystrate trees question, one would find that I reached my destination in 171 hours, and the journey was 2850 miles, so one would mistakenly conclude that I was traveling at just over 16 and a half miles an hour. This is exactly the problem with the extrapolation used in some creationist citations of polystrate fossils, and it is simply illogical.



  3. Where has all of the sediment presently going into the oceans gone?

    Over 27 billion tons of sediments enter the oceans each year. Even assuming a constant flow of this pace, the current sediments on the ocean bottom would have accumulated in only 30 million years.



    Thomas H. Faller:

    We dealt with this one recently. The false part of the question is "the current sediments on the ocean bottom". In the other version of this question, a figure was given which was supposed to represent an average thickness of sediments on the ocean bottom. This question omits even that data and takes it for granted that the comparison is valid.

    What the question omits is that the sediment layer on the ocean floor varies greatly, from inches near mid-ocean righes, to miles deep on the continental slopes. Except for the Atlantic, which is only about 65 million years old, the ocean floor continually renews itself, taking its sediment load down into the crust as it is subducted at plate boundaries. So even allowing the rate of sediment deposition as constant (which it isn't - it varies with tectonics and the shape and distribution of continents), there are more than enough sediments in the ocean to be accounted for by continental erosion.

    The question for the creationist is to explain the difference in ages between the oldest sediments in the different oceans.


    John Harshman:

    I think it's important here to note that there are two main sources of sediment "on the ocean bottom". Terrigenous sediments (being eroded and transported from land) are found close to land, mostly on continental shelves and slopes. The great majority of the ocean bottom receives no terrigenous sediments, but gets only the shells and tests of pelagic microplankton. And there's not really very much of that, and much of it dissolves over time. So this question is comparing two entirely separate phenomena: the large amount of sediment entering the near-shore regions, and the small amount accumulated in the abyss.

    So. What happens to all the terrigenous sediment entering the oceans? This is a fine example of the White Queen syndrome, because another question in the set asks why marine fossils are commonly found on mountain tops. What happens to much of this sediment is that it is eventually incorporated into the continents.

    [Creationists also need] to explain the very interesting layering of siliceous and carbonaceous ooze as we progress away from mid-ocean ridges, and as we pass the carbonate compensation depth. (I've seldom seen this layering mentioned in attacks on flood geology, and it ought to be brought up more often.)


    Floyd:

    If there were no mechanisms by which sediment was removed from the ocean floor, this would indeed be an interesting anomally. It has nothing to do with biological evolution, of course, but it would still be interesting.

    The problem with this question is that there are mechanisms that remove sediment from the bottom of the ocean. The most notable examples are found along the Pacific coasts of North and South America, where the continental plates are actually over-riding the ocean floor, pushing the oceanic plates "downward" toward the center of the earth, where the earth's interior heat melts them and causes the molten rock to boil to the surface and form volcanoes. The linear arrangement of the North and South American volcanoes (including the extinct volcanoes of alifornia,) is parallel to the coast because these continents are moving in roughly the same direction.

    http://www.ucmp.berkeley.edu/geology/tectonics.html contains links to information about the history of plate tectonics, the mechanisms that drive it, and some very nice animations of the movement of continents over the last 750 million years.



  4. What caused the Ice Age?


    Mike Dworetsky:

    I can't figure out if this question is meant as a challenge to evolution (it isn't) or is simply asked as a matter of curiosity and an inability to use Google or other web search engines.

    However, the current consensus, backed by a lot of geological and astronomical evidence, is that ice ages are brought on by variations in the Earth's orbit, and in the inclination of the Earth's axis. The main influences are variations of orbital eccentricity on a scale of 100,000 years and variation of the season of perihelion or nearest distance to the Sun. This currently happens in January, but if it occurred in July, northern winters would be much harsher and ice could build up. The period of one perihelion cycle is 21,000 years. These are called Milankovitch cycles.

    See http://aa.usno.navy.mil/faq/docs/seasons_orbit.html for more details.

    There may be secondary effects due to environmental factors such as dust or smoke from volcanoes. These could lead to abrupt starts or finishes of ice ages.

    We are currently in a warm interglacial period when Europe, Russia and North America down to about latitude 42 degrees are perfectly habitable. In about 10,000 years this may no longer be the case.

    There may be other reasons why Earth undergoes ice ages now, and did so in the distant past, but in between did not have ice ages. Fred Hoyle theorised that ice ages start to occur whenever a continental land mass occupies one or both of the poles, and cease when plate tectonics moves the continent away from the polar regions. The continent acts to spawn huge glaciers that melt and cool the oceans, making ice ages easier to trigger. Antarctica was obviously once temperate or even tropical, according to its fossils, so it must have moved from there to its present position. Currently, this additional theory of the overall cause of ice ages has plausibility but not widespread acceptance.


    Ken Shaw:

    That is not the only thing caused by a continental landmass occupying covering a pole. The covering of the land mass with a thick ise sheet removes a significant amount of water from circulation. The ice covered land changes the albedo of the planet. These two factors should result in a world wide cooling until the continent drifts far enough away to melt the glaciers.


    Thomas H. Faller:

    A drop in the average global temperature. This could have been caused by a number of things, since the AGT depends on things like solar heat input, the earth's albedo, composition of atmospheric layers, distribution and size of continents, interior heat flow and whether the dinosaurs farted enough.

    One suggestion is that until recently, the North Pole was not encircled by land enough to cause a change in pole-to-tropics oceanic circulation, which would allow polar ice to build up, making other triggers more pronounced. But Ice Ages have come and gone before the recent age, and there may be long term effects like the wobble of the Earth's axis, solar output variation, and volcanic activity that trigger them. We'll just have to wait for the next one to find out.

    A question for creationists is why do we not only see evidence for recent glaciation, but for mile-thick glaciers back in the Precambrian? How long would it take for those glaciers to form, melt, form, melt and have all of that other sedimentation going on in between?


    Floyd:

    Orbital forcing seems to be a major source, but planetary albedo, and perhaps even the location of North Atlantic deep-water upwelling may also have played a role. Some researchers have even suggested that a rise in air temperature could cause melting of the arctic ice cap, and the addition of very cold fresh water to the North Atlantic may have been a significant trigger for increased glaciation in northern Europe and North America.

    Again, this question doesn't seem to have any bearing on the validity of evolution. Evolution was occurring long before the Pleistocene ice ages, and has continued unabated through them and into the present.

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