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December 19, 2008


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Yet, as Kuenen suggests, there is feedback at work here, lithospheric processes being themselves influenced by the games that sand plays across the Earth's surface, games whose rules are determined by the size range of the grains.

Has there been any computer simulation work done on lithosphere evolution with a variety of sediment size ranges as inputs?

Also any idea what the sediment size ranges on Mars are? It would be interesting to see whether Martian crust has broken down to sediment size ranges of similar proportions to earth and how that has influenced features on Mars in at least the environments we are identified so far.

Suvrat - thanks for the comment and good to find your blog (since we've been talking about the international geoblogosphere).

Re your question on lithosphere evolution simulation, I really can't answer, since I'm not intimately plugged in to what research projects might be relevant. Does anyone else out there know of this kind of work?

As for Mars, it's an interesting point (I was thinking of continuing the post with extraterrestrial systems, but decided to leave that for another day). Anything that I've seen (and of course there's not a lot of hard data) suggests that grain size distributions on Mars are similar to Earth's. But while the processes that operate on Martian sand are the same as on Earth, the circumstances, and therefore the results, are different. Today, lower gravity and a much thinner atmosphere have a strong influence on sediment transport. However, in the past on Mars there was clearly liquid water, a thicker atmosphere, and volcanism; whether or not there was ever anything like plate tectonics remains the subject of debate - there is little evidence other than one way of interpreting the structure of the magnetic field. It's possible, that before the planet cooled off, some kind of tectonics was operating (see, for example, http://www.colorado.edu/news/r/6c0a44b4e94740d96f138d039f28718f.html, from just a few days ago).

If the distribution of sand grain sizes on Mars is similar to Earth's, then that would suggest, in the past, a similar conspiracy of sand sources. There has been a lot of work done on today's Martian sand transport, using the extraordinary results from the Rovers, the Orbiter and Phoenix. Martian dunes and dunefields are similar but different - see, for example, http://www.mars-dunes.org/uploads/abstracts/1486.pdf, http://www.lpi.usra.edu/meetings/7thmars2007/pdf/3048.pdf, and http://www1.nasa.gov/vision/universe/solarsystem/mer-011105_prt.htm.

It's also fun to remember that, in 1974, Ralph Bagnold, the "father" of the analysis of sand transport mechanisms, and Carl Sagan, were predicting the behavior of sand on Mars before the first NASA missions.


thanks for that Martian discussion and the links. looking forward to reading more on your site.

Hi Michael and seasons greetings too - it's your erstwhile neighbour checking in with some sandy stories and queries related to current whereabouts (Australia). We've been hotfooting around the Outback examining rocks large (including Uluru. Mt. Connor and the Olgas) and small, enjoying the scenery, avoiding close contact with the wildlife and drinking plenty of the local liquor. Top pick for sand was probably King's Canyon, eastish of Alice Springs. It's a dramatic sandstone formation rising out of the flat bush where wind and water erosion has created a whopping great cleft with dramatic cliffs to match. At the top are some attractive beehive shapes, and in places the ripple patterns of a long-dry seabed. If you break open some of the reddish-brown fragments of sandstone, you are rewarded with a small explosion of white sand, although this behaviour is discouraged by the visitor signboards, which claim that the sand is an eyesore!

The blurb says said sand is 330-440 million years old. How old is that, in sand terms?

Have to sign off for now - off to a trivia quiz at the Rugby League Club with my Ma and Pa - but look forward to more sandblagging later.

Love to Carol,


Hi Kieron and Jo - thanks for the comment and it's good to know where you are, or, at least, were! And, of course, I'm envious of both. I have to say that I take great exception to sand being designated an eyesore.

The sandstones of King's Canyon are old, but not very in the grand scheme of things. Not far from there (well, in fact quite a long way, since nowhere in Australia is close to anywhere else)are the Jack Hills of Western Australia that are constructed out of sandstones that are around 3 billion years old. But that's not the end of the story - there are individual grains in those sandstones, made of the durable mineral zircon, that are the oldest home-grown (i.e. not extra-terrestrial) things that we have ever found. At close to 4.4 billion years old, they were formed within a million years or so of our planet's birth. Through clever geodetective work, they tell us extraordinary stories of the Earth's early days.

Enjoy - and keep us posted, so to speak!

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