Mike Hall: Earth history along ocean cores
Mike Hall describes the revelation of glacial and interglacial cycles in deep ocean cores in the late 1960s and early 1970s.
Well, straight away I think the – one of the most exciting times certainly in the late ‘60s, early ‘70s, where we produced the longest core – data from the longest core, which was V28238. And it went across the Brunhes-Matuyama boundary, I think, and through up to about a million years. That was quite an exciting time as we were progressively moving down this core, seeing how the various isotope values were changing and going through various ice ages which people hadn’t seen before. That was a particularly exciting time.
You said we were progressively going down. Is that the direction in which you worked?
Yes, we worked from the top downwards at that time and we were just seeing how far we could get down the core. Obviously cores have a finite length and we worked down the whole of this core, and I think it got down to about a million years. And I – I remember when we’d finished it, having a – a party at Nick Shackleton’s house and we actually did A4 sheets for every thousand years and we had a whole sort of series going round the room so that people could actually see it, this record that we managed to – to produce.
How long did it take you to work all the way down from the top to the bottom of the core?
Oh goodness [laughs], I think it was a number of years, because at that time we were probably only doing maybe ten – ten samples a day. So it was – I can’t remember how many data points there were but certainly it was – it was quite some time to produce that.
To what extent did the results become apparent as you were going along? Or to what extent did you have to wait till the end and sort of – to put it all together?
Well, as you go – we started at the top of the core and were gradually working down it. So when we did the first ten measurements you could see that these were – were probably fairly flat, being a sort of interglacial period, and then you would find – do the next two or three measurements and they would be getting heavier, and therefore you’d be going down to a glacial. And then at the bottom of that you’d find – the next day you’d do a few measurements and be coming up to another interglacial. And you’d be going back in cycles between glacial and interglacial periods and it was interesting to see how many glacial cycles there were.
You’re almost following it. Following the history of it day to day.
Yes, exactly. You didn’t know what you were going to find from one day to the next, really.
How quickly were you going back in time? So over a week, if you were doing ten samples a day, let’s – perhaps that’s fifty a week. How far would you move in terms of time down the core, roughly?
I would probably say that this core – maybe we’re going 40,000 or 50,000 years a week, I should think, something of that order, I think. I think it was probably one sample maybe every thousand years at that time.
- Interviewee: Mike Hall
- Duration: 00:02:49
- Copyright: British Library Board
- Interviewer: Paul Merchant
- Date of interview: 1/13/2012
- Shelfmark: C1379/59
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