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Description
Pentz introduces the idea that the present is the key to the past. To support this view he poses some questions about fossils. By studying the modern environment we have clues as to how fossil sedi
...ments were formed.
Wilson emphasises the view that the present is the key to the past by showing that the rocks are only a static record of a period in geological time.
| 1 | 00:00:00,000 | 00:00:04,000 | Michael Pentz: If your idea of a geologist was of somebody pottering about with… |
| 2 | 00:00:05,000 | 00:00:08,000 | ..a little hammer collecting bits of rock then I expect you had a bit of a… |
| 1 | 00:00:09,000 | 00:00:12,000 | Chris Wilson: Well these sand dunes have been produced by wind blowing… |
| 3 | 00:00:09,000 | 00:00:11,000 | ..surprise from the last four course units because there after all we were… |
| 4 | 00:00:12,000 | 00:00:15,000 | ..dealing with the earth as a huge process, a large scale process, |
| 2 | 00:00:13,000 | 00:00:16,000 | ..sand from the beach, mainly by the westerly winds, and you can… |
| 5 | 00:00:16,000 | 00:00:19,000 | building up our picture of its structure, of its dynamics… |
| 3 | 00:00:17,000 | 00:00:19,000 | ..see they stretch off into the distance towards the east. |
| 4 | 00:00:20,000 | 00:00:24,000 | (Chris Wilson) If we continue the sequence we come to another low marshy area… |
| 6 | 00:00:20,000 | 00:00:23,000 | ..mainly from physical data, but not only from physical data. |
| 7 | 00:00:24,000 | 00:00:28,000 | You see an essential part of the data we need to understand the Earth is, |
| 5 | 00:00:25,000 | 00:00:28,000 | ..which is a much older equivalent to the calm water area… |
| 6 | 00:00:29,000 | 00:00:32,000 | ..we saw between the storm beach and the sand dunes. |
| 8 | 00:00:29,000 | 00:00:33,000 | quite simply, data about rocks, like these rocks in front of me here. |
| 7 | 00:00:34,000 | 00:00:36,000 | Chris Wilson: And they’re certainly not static, as you can see, |
| 9 | 00:00:35,000 | 00:00:40,000 | Question is though can we, in some way, by studying what is… |
| 8 | 00:00:37,000 | 00:00:40,000 | this hut here has been half buried by the blowing sand. |
| 10 | 00:00:41,000 | 00:00:45,000 | ..going on now today, find out anything about how these rocks were made? |
| 9 | 00:00:42,000 | 00:00:46,000 | But generally the net movement on the sand is out towards the sea. |
| 11 | 00:00:46,000 | 00:00:50,000 | Can we, for example, find what did this? |
| 10 | 00:00:49,000 | 00:00:51,000 | (Chris Wilson) Think back to where the first specimen… |
| 12 | 00:00:51,000 | 00:00:54,000 | Perhaps some strange animal did something strange to that rock… |
| 11 | 00:00:52,000 | 00:00:56,000 | ..was collected out here near low tide mark. I also collected specimens… |
| 13 | 00:00:55,000 | 00:01:00,000 | or can we discover how this hole which looks rather like a hole made… |
| 12 | 00:00:57,000 | 00:01:01,000 | ..from the storm beach here, then walked across the calm lagoonal area, |
| 14 | 00:01:01,000 | 00:01:05,000 | ..by a great fat worm might have been made sometime in the distant past? |
| 13 | 00:01:02,000 | 00:01:05,000 | collected another specimen from the sand dune, and finally… |
| 14 | 00:01:06,000 | 00:01:08,000 | ..ended up in the salt marsh and had a mud sample there. |
| 15 | 00:01:06,000 | 00:01:10,000 | Now this is exactly what Chris Wilson, Dr Chris Wilson, will be doing… |
| 15 | 00:01:09,000 | 00:01:12,000 | Now having collected these samples, one takes them back to the lab. |
| 16 | 00:01:11,000 | 00:01:15,000 | ..in the programme, where you will find him shortly exploring a beach… |
| 16 | 00:01:13,000 | 00:01:18,000 | Now, how would we go about analysing these samples from a geological point of view? |
| 17 | 00:01:16,000 | 00:01:20,000 | ..off the coast of Norfolk, a beach where sedimentary deposits are being laid down. |
| 17 | 00:01:19,000 | 00:01:23,000 | Well for a start one could look at the chemical composition or the mineral composition. |
| 18 | 00:01:24,000 | 00:01:28,000 | But the easiest thing to do is to measure the mechanical composition, |
| 18 | 00:01:26,000 | 00:01:28,000 | (Chris Wilson) Now this is rather interesting, we haven’t found the… |
| 19 | 00:01:29,000 | 00:01:33,000 | the grain size distribution of the sand. Now, this is fairly easy to do… |
| 19 | 00:01:29,000 | 00:01:33,000 | ..animal that was making the little worm casts on the surface but here’s… |
| 20 | 00:01:34,000 | 00:01:38,000 | ..with a loose sediment like this one while using a stack of sieves. |
| 20 | 00:01:34,000 | 00:01:38,000 | ..an interesting spiral pattern which must have been made by some animal, |
| 21 | 00:01:39,000 | 00:01:43,000 | These are arranged with the coarsest mesh size on the top of the stack… |
| 21 | 00:01:39,000 | 00:01:43,000 | I don’t know what, that found a particularly rich layer, rich in organic material, |
| 22 | 00:01:44,000 | 00:01:47,000 | ..and the finer sizes then occur progressively downwards. |
| 22 | 00:01:44,000 | 00:01:48,000 | and it’s just systematically grazed along this layer, gobbling up… |
| 23 | 00:01:48,000 | 00:01:53,000 | The technique is quite simple… The sand is tipped in at the top… |
| 23 | 00:01:49,000 | 00:01:52,000 | ..the organic material and then passing out the sediment that it couldn’t digest. |
| 24 | 00:01:53,000 | 00:01:57,000 | This is rather a beautiful example which I’ve never seen on a beach before. |
| 24 | 00:01:54,000 | 00:01:57,000 | ..and the whole thing is then shaken, actually it’s shaken mechanically, |
| 25 | 00:01:58,000 | 00:02:00,000 | because one doesn’t want to stand there for half an hour doing it. |
| 25 | 00:02:00,000 | 00:02:05,000 | Well, let’s see if we can find the little beast that makes these worm casts. |
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