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Phil: I'm Phil Bradfield. I'm an Associate Lecturer with the Open University, a tutor with the OU.

Saskia: I'm Saskia Van Manen, and I'm doing a PhD at the OU in the Department of Sciences.

So what is it that you hope to get out of today?

Phil: Well, I suppose there's two things really. I mean one thing is that people have heard of Coast; they’ve seen the TV programmes. And Coast is produced in association with the OU, so we’re showing them about the geology of Britain.

Saskia: I would say we’re also trying to encourage a general interest in science and maybe, in particular, more about geology.

And you're standing here with tables full of different rocks of different colours, different shapes. What is that you're able to tell people about them?

Phil: Well we’ve split them up into three sections. We've got sedimentary, igneous and metamorphic rocks, here. And people come along and they ask us things about it. I mean, they might pick up one of these rocks and we let them have a look at it with the hand lens and find out what it’s made of and we're testing them with acid and so on.

Saskia: Well, we've split them, basically, by how they've formed, and we can tell them how they formed - we can explain that in more detail, and then we can also point out interesting features in these rocks, or we can say what they're used for nowadays.

And do people look at them and say they remind me of such and such a coastal walk that they’ve done?

Saskia: They definitely do, especially the chalk reminds everybody of the Cliffs of Dover.

Phil: Well, yes, I've had two people just come up to me, just now, saying, ‘Ooh that looks just like the rock I found on the beach near home’, just now, so we start talking about it and take them into the geology a bit more.

The people who you have been meeting here today have they been coming from a long way away or are they local?

Phil: Well the last lady came from Germany, so I suppose that’s not very local. We've had people from the south coast, from Kent, there was a lady who was talking about her home in Turkey, just now, so we've had quite a few different people turn up, yes.

So on the table here there's some flint, there's some chalk from Dover. The flint says it’s from Sussex. I mean what is it that I can learn specifically about those two things?

Phil: Right, well, most people recognise chalk. It’s dead easy to recognise so we don’t need to do much on this. But one thing we can do is add some acid to this, and if you add acid it fizzes away merrily, so we can show that it’s a rock that’s made of calcium carbonate, chalk. And you probably know that the flint is often found in the chalk. In fact, this sort of flint is always found in the chalk. And flint’s a completely different sort of rock, it’s a silica; it doesn’t fizz. If I put the acid on this, it won’t fizz at all. So we can show them the basics of some sedimentary rock geology.

But if you imagine the White Cliffs of Dover, and you can see, what, a hundred feet of chalk there, it goes down underneath that, a lot further down, several hundred feet of chalk, and all of this chalk is made from microscopic organisms, things called coccoliths, which are tiny little calcareous plates of micro-organisms of algae that have slowly settled down and formed the chalk over millions of years. And the process is going on today in warm seas around various places around the world, like the Bahamas, you get the same process forming the chalk. It’s one of the principals of geology that processes that went on in the past are going on today and doing the same thing.

And over here on the other table, there's a nice lump of basalt from Northern Ireland, what can you tell me about that one?

Saskia: Well, as you can see, it’s a very nice fine-grained black rock. It’s of volcanic origin. It cooled very quickly, hence the very fine crystals.

And it’s described as an igneous rock.

Saskia: Well the main three rock types that we have are metamorphic rocks, igneous rocks and sedimentary rocks. Igneous rocks are always of volcanic origin, whether they actually come out of a volcano or are just hot bodies of magma that move up and cool underground, it doesn’t matter, they're still igneous.

Sedimentary rocks form when other rocks erode, and then that just gets deposited, and by applying pressure to it they form rocks.

Metamorphic rocks are when igneous and sedimentary rocks undergo changes due to heat and pressure. So that’s the different types and that’s how we tell them apart.