Jo’burg life is never dull…

Posted on October 11, 2007 by Chris Rowan

It was an interesting day yesterday.
Firstly, there was a student demonstration outside campus over plans to increase tuition fees next year. Protestors were not allowed on campus, and after a couple of hours of singing and banging drums it seems several students tried to break through the gates, at which point the police moved in and enthusiastically dispersed them with salvos of rubber bullets and tear-gas. Since the geology department overlooks the main entrance, we all got a grandstand view; fortunately, it seems that no-one was injured.
Ten minutes later, we were plunged into darkness due to a “load-shedding” exercise by the power company: increased energy usage in the current cold and damp weather is apparently straining the grid to breaking point, so successive districts around the city are being subjected to 2 or 3 hour rolling blackouts to prevent the entire system melting down.
Living here is a real eye-opener sometimes.

Categories: bloggery

Palaeomagnetism: from drilling to publication

Posted on October 9, 2007 by Chris Rowan

I thought that a useful follow-up to the musings on trust and access to scientific data prompted by the other week’s tale of near disaster would be to describe in detail how the measurements that I make in the lab are distilled into the results reported in a typical scientific paper, so you can see exactly how much information is included – and how much is left out. As an added bonus, you get to discover exactly what it is I do all day. It might be worth your while reading some background information before you continue.
The starting point for any palaeomagnetic study is a trip to collect drill cores. Having found a suitable sequence of lavas or sediments of the right age and location, we sample a number of sites at regular intervals through that sequence, collecting five or six cores from each site. We want duplicate samples from each site to check for consistency, and the sites spread across a large enough thickness of rocks to properly represent the long-term geomagnetic field direction, rather than a quirk of secular variation.

pmag1.png

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Categories: basics, fieldwork, in the lab, palaeomagic

Say hi to a new Scibling, and help out an existing one

Posted on October 9, 2007 by Chris Rowan

Laelaps has joined the collective; if you aren’t already familiar with Brian’s prolific and informative musings on things palaeontological (although he probably wouldn’t spell it like that) go and check out his new digs. Palaeontology is almost geology, after all.
Meanwhile, Shelley is one of 20 blogs in the running for a $10,000 blogging scholarship. She has assured me that she won’t spend it all on mimosas (which, after her performance at the Scibling shindig, was a slight concern), so if you, like me, are a fan of her rather nifty neuroscience blog, go and vote for her. If you’re not a fan, go and read it, become one, and then go and vote for her.

Categories: links

Northern Hemisphere rules

Posted on October 7, 2007 by Chris Rowan

The last four years have not been particularly kind to the English rugby fan, so to say that I wasn’t expecting much from the Rugby World Cup quarter final between England and Australia would be an understatement. In fact, I felt I was being rather optimistic in hoping that we’d give them some sort of game and not get slaughtered, like we were against South Africa a couple of weeks ago. But when it really mattered, the English team stood up to be counted, and then some.
It wasn’t pretty, but it was proof of that backs may look pretty when they’re running in the tries, but forwards win rugby games, because you can’t do anything if you don’t have the ball (of course, I was a forward myself, so I may be a little biased on that score). English play at the breakdown was the best I’ve seen for four depressing years. And now we get to gloat at the Aussies for another four years.
Then, just to make a good day better, the French beat the All Blacks. That’s a whole lot of lording it over the supposedly far superior Antipodeans to look forward to, and no doubt a large vat, nay a lake, of sour grapes to savour.

Categories: rugby

The heart of the fault zone

Posted on October 6, 2007 by Chris Rowan

For all that we currently know about earthquakes and faulting, seismology remains primarily a descriptive science. We can tell where an earthquake occurred, and how powerful it was, but we still don’t understand why some ruptures trigger failure over a large section of a fault, and others do not. Plate tectonics allows us to predict the overall motion across a fault zone, and even the type of faulting that is needed to accommodate it, but we can’t predict whether that motion will be expressed by a single large earthquake or dozens of little ones.
A large part of the problem is that we don’t know much about what faults are like where it really matters: although many large faults break and deform the Earth’s surface, the initial rupture in an earthquake always occurs several kilometres below, where increased temperatures and pressures make rocks behave somewhat differently that they do in the part of the fault we can see and touch. Geophysical techniques can tell us roughly where the fault zones are, but lack the resolution to tell us much about a feature which may only be tens of metres across. Which is why the rocks pictured below are so important: they were collected from 3 km below the surface, right in the heart of the San Andreas Fault.

SAFOD.jpg

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Categories: earthquakes, geology, tectonics