Magnetic microbe. Source:

By Kelly

Here at oncirculation we are trying cover a range of topics from different perspectives across the Earth Sciences. It’s about embracing what is out there on Earth….and with that in mind I will attempt to write something about the school seminar from last week. I should note it was given by our director so I am putting my neck on the chopping block a little, as I may be committing career suicide if I get this wrong. But I’m fearless (gulp) so let’s talk (and copy and paste from his abstract) about paleomagnetism. According to Professor Andrew Roberts paleomagnetism is as vibrant a discipline as when it was being used to study magnetic reversals around spreading centres at mid-ocean ridges. While it has been fundamental to “Earth science through helping to establish the global plate tectonic paradigm and … for calibrating geological time”, there are still many exciting applications and nuances in interpreting the history of Earth’s geomagnetic field.

I for one did not know that certain particles can “retain stable magnetizations for periods exceeding the age of the Earth”. Well that certainly makes my own radiocarbon dating seem a little limited at 50,000 years. What was also a pleasant surprise is the biological component to one the corner stones of modern geology. “Within sediments and sedimentary rocks, there are many processes that give rise to interactions between microbes and minerals that can produce magnetizations with varying ages”. As is often the case, the biology can confuse the record somewhat, yes it is the beloved “vital effect” rearing its ugly/beautiful head (depending on how  you perceive the value in being alive).  Two biologically mediated processes dominate. The first is the degradation of organic matter that can dissolve the minerals of interest, and second, and perhaps coolest (my words not his) is the ability of certain microbes to biomineralize magnetic minerals . While this aids the organisms in finding the ideal habitat for growth, these anoxic muds tend to also dissolve the minerals that remain when the microbes die, confounding the magnetic signature.

Here in Australia the PhD is short, partly because we are not required to take classes as is the case for our U.S counterparts. I think that this is a shame as we finish without the same breadth of knowledge, having focussed so very early in our scientific apprenticeship. Attending seminars like this one are vitally important, to help broaden our knowledge as Earth scientists….and to make sure the director sees you attending seminar. To read the abstract so that you too can earn brownie points for when you need an extension on your PhD, click here.