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After suggesting that clear explantion of science is fundemental to our overall cause, I'm know forcing myself to do something I will probably regret!

Anyone got any questions about geology they want aswered?

Please bare in mind the following: I am a sedimentologist not a palaeontologist (I don't do dinosaurs, so requests for fossil identifications will not get much further than "ammonite" or "gastropod"). Otherwise I will do my best to answer any and all questions. I would prefer specific questions not general ones, if you ask for an explantion of plate tectonics I'm quite likely to just suggest you look it up in a book! I'm also a "proper" geologist so I'm likely to be a bit sketchy on the finer points of othe pet theories of "creation" geology (...they definitely weren't on the syllabus at University).

I note that we have a number of other scientific specialities represented in the forum, perhaps they to would like to launch their own FAQ threads?

Perhaps if this is successful might mod's consider making this a sticky/pinning it?

Hi Jon,

How about going into the various evidences that support the currently accepted age of the Earth (approx. 4½ billion years) and why young (and old?) Earth creationist claims are wrong?

Kyu

That's a great idea. I have to admit I gave up geography after O level and have never really studied geology at all. I'm not hot on physics either.

I failed my O Level (IIRC I got a "U") ... but my excuse is I was a lazy [expletive deleted]

Kyu

Great starting place - especially the radiochemical evidence which does not require calibration from the fossil record (despite the misleading claims of some creationists). This is good because it has nothing to do with evolution and so provides an independent refutation of YEC.

Could you provide an explanation of how age is calculated from the ratio of isotopes and how it does not depend on the initial rock compostion?

Perhaps 'why geological features such as the grand canyon could not have possibly have been created by a global flood' would be a good idea then.

Dating the Earth.

The age of the Earth is currently estimated to be around 4.5 billion years. This estimate is actually based on a compromise between the radiometric dating of lunar rocks and meteorites, and Earth materials. The oldest Earth materials currently dated are zircon crystals from the Black Hills in Australia. The oldest date at the moment is 4.404 +/- 8 Myr (Wilde et al., 2001).

For a readily understandable break down of radiometric dating try the link below:
http://en.wikipedia.org/wiki/Radiometric_dating

Scientists use zircons because they contain a relatively high amount of naturally occurring radiogenic elements, uranium and thorium, and also because zircons are chemically and physically stable during erosion and deposition being able to survive more than one such cycle. Therefore a zircon crystal is essentially a geological clock that starts ticking on formation in its parent rock (granite) and continues to tick even when eroded and incorporated into a new sedimentary rock. The zircons dated in Australia come from metamorphosed sedimentary rocks. This means that rather than just looking for a very old igneous rock, which probably wouldn't have survived this long, you can look for very old sedimentary rocks, which are themselves composed of material derived from even older parent rocks.

Unfortunately creationists are willing to invoke near enough anything (except God!) to explain away the erroneous, in their eyes, ages given by radiometric dating. For example Humphreys et al. (2004) suggests “episodes of highly accelerated nuclear decay occurring within thousands of years ago” ([edit]... it also appears creation scientists can't write decent english). This idea is actually based on some early 20th centuary science ideas that were formulated before radioactive decay was properly understood.


The one thing they won’t stoop to, it seems, is omphalos hypothesis (because its a 'faith' position), which actually I wouldn’t have any trouble with!

Humphreys, D.R., Austin, S.A., Baumgardner, J.R. and Snelling, A.A. (2004) Helium Diffusion Age of 6,000 Years Supports Accelerated Nuclear Decay. RSQ, Vol 41, No 1.

Wilde S.A., Valley J.W., Peck W.H. and Graham C.M. (2001) Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature, v. 409, pp. 175-178.

Well, I might be able to help if anything comes to mind . Bearing in mind though that I've just jumped ship from an obscure branch of particle physics to condensed matter theory, so my knowledge of cosmology is a bit limited. (And don't get me started on the string theory landscape...)

Incedentally, I should be getting a bit more active over the next couple of weeks (with a slight hiatus around the first fortnight of August [1]) as I'm actually going to get hold of my own computer and not have to do stuff in quick snatches at work.

[1] Got roped into helping out the science tent at the Welsh National Eisteddfod. And giving a popular lecture. On particle physics. In Welsh.

EDIT:Wrong smiley.

Flood Geology

http://en.wikipedia.org/wiki/Flood_geology

Okay I'm abusing Wikipedia, but it says pretty everything there is to say, and its readable. The philosopical objections at the bottom make the case that "flood geology" is purely a faith position, which is essentially what we are attempting to get creation scientists to admit to alot of the time (once they admit that the game is up, its RE not science)!

The ultimate problem with flood geology (and creation science in general) is that they just come up with untestable hypothesies to explain away each bit of scientific information.

As a rule flood geology relies overly on the idea of catastrophism to try and squeeze all the Earth's geology into the small temporal space they've decided it fits in. Catastrophism is the idea that single large, low frequency, high magnitude events (i.e. a large storm) have a significant control on the development of the landforms we see around us and are what we see often preserved in the geological record. Conversly gradualism says that smaller and more fequent events are more important. However, in earth science it is generally recognised that both gradualism and catastrophism play parts in the developement of landforms and the geological record.

Most deposits that are the result of a catatstrophic event tend to exhibit diverse range of particle sizes (sand to boulders) and the particles may be angular. However, all this depends partly on what the eroded parent matrial was like! For example a storm bed in a beach profile will contain a lag of larger particles like broken shells and pebbles, while finer material will be absent becuse it has been swept away. As a rule of thumb the longer material has been in sedimentary system, such as a river, and the furthur it has been transported, the smaller its size will be and the more rounded any particles will be. The pebbles on beach are rounded because they have been there a long time, exposed to wave action, and possible been transported a long way. The scree on a mountain slope is more angular because it is eroded direct from that mountain and has not travelled very far.

Creating a large canyon like the Grand Canyon purely by catastropic processes (i.e. very quickly) would likely result in a flood outwash plain, which close to the canyon mouth should contain alot of large, angular, poorly sorted sediments. While further away the sediments would become finer. I'm not sure, but I'm fairly certain in reality that is not the case, but I have no idea what theory has been concocted to explain that away....

There are areas of the world where catastrophic lake bursts have created places like the Washington Scablands.

[edited for clarity]

This is probably a bit of topic, and I suspect should be under a new thread, but since we are talking about Geology, keep an eye out for "Journeys into the ring of fire", this Wed. (12/7) at 9.00 pm on BBC 4, which is presented by the excellent Dr Iain Stewart. Quite a lot of geology in it and this time it's all about the so-called "Pacific Ring of Fire" which I remember learning about at school while doing O-Level (GCSE now) geology. Compulsive viewing in my opinion !

His last series "Journeys to the centre of the Earth" was all about the geology of the Med. and how it has affected human history in that area. There was a very good episode in that series on beliefs, which included a bit on why flood geology was rejected in the 19th century by the likes of Hutton and Lyell, and why we now believe that natural events are not "Acts of God" !

For those with freeview its on channel 9. On dig. satellite it's free to air on Sky Digital channel 116. If you haven't got either then fear not. It will probably be repeated on BBC 2 at some stage.

Jon: What would you say are the best predictions made by geology? I'm talking the geological equivalent of the human chromosome that's identical to two chimp chromosomes, or the vitamin C pseudogenes in primates.

Having a few things like this up for each "disputed" area of science would be a superb way to respond to creationists.

Corkscrew,

I hope that you don't mind throwing my pennyworth in but, out of the top of my head, i guess plate tectonics/continental drift must be pretty high in the stakes.

It accounts ecological changes pushing evolution (and, I guess, mass extinctions such as at the end of the Permian) but also for geographic separation of species prompting further evolution and diversity amongst species.

It also basically accounts for most (if not nearly all) of what we see amongst major geological formations and structures which in turn undermines the creationist nonsense.


Roger

That's a superb model, yes, but not strictly speaking a prediction. I'm thinking more of a situation where someone has said "hey, you realise that if this model is true we'd expect to see {really unexpected thing}?" and then gone out and found said thing to be true.

I have no idea what the chronology is, but, if it wasn't known at the time that the Earth's mantle was molten, and plate tectonics predicted that discovery, and then that discovery was made - that would count as a strong prediction.

Off the top of my head I can't honestly think of a situation like that in geology. Geology has rather a long history and has for the majority of that time been an observational science. I think broadly speaking most fundamental truley unanswered questions (ie those we only have a best guess for based on data from remote sensing of one form or another as opposed to observation) in geology, such as what is the nature of the mantle & the core, aren't really going to answered any time soon. There are predictions for plate movement and climate change, but all of these are happening on a "geological" timescale. I suppose the KT boundary "predicted" the presence of the Yucotan crater, but its not really a prediction based on a "model" as such.

I suppose on a mundane level oil prospecting could be seen as the use of geology to make limited predicitive assumtions as to the presence or absence of oil. One particular technique know as sequence stratigraphy has become a very important tool and is very often right ( http://en.wikipedia.org/wiki/Sequence_stratigraphy ). Also modern paleontologists do target their excavations when they are looking for animals from particular epochs.

Thanks Jon. Any chance you could go into more detail on the Yucatan crater thing? That sounds like at least a Tiktaalik-level prediction. Was the crater explicitly searched for due to a property of the KT boundary? Was it possible to derive any information about its location? How was the correspondence between crater and boundary conclusively established?