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essay crises abound
In... nine hours' time I am giving a talk to a bunch of 11yos about why geology is awesome. Consequently I have just finished putting together a presentation, and I am going to find it easier to type my notes on what to say for each slide into this box than I would do to put it anywhere else. I suspect it is pitched entirely wrong but um I am out of cope for doing anything else.
In related news, I Will Never Leave This Basement Again, But Maybe I Am Finally Getting Data?
Slide 1: Inside (and outside) the Earth
I'm a volcanologist. This means I spend most of my time sat in a basement handling grey rock powder, but more importantly it means I have a list of my Top Five Favourite Volcanoes.
Slide 2: Mount Erebus, Antarctica
Slide 3: Ol Doinyo Lengai, Tanzania
Slide 4: Mount Ngauruhoe, New Zealand
Slide 5: Skaergaard, Greenland
Not an active volcano - but it's a fossil magma chamber. It's exciting because the magma chamber got filled up in one go, then was sealed off - so we can see how everything cooled down over thousands of years. One of the results is the beautiful layering you can see in the mountains - compare it to the size of the helicopter: it's huge! However, in order to do any useful work on it, you end up in dry camp in the middle of nowhere for most of a summer, and you have to carry rifles at all times in case of polar bears. (Will I give them nightmares if I tell them how to kill polar bears?)
Slide 6: Hawai'i
Hawai'i's really famous - it gives us the names of lots of types of lava, and it has absolutely beautiful fountaining eruptions. Also, Pacific Islanders have oral history about the goddess of the mountain, and how she fell out with her sister and they had an argument - and you can actually match these stories up to events we can identify from the different lava flows. Also, geologists try really hard to have their meetings there, as an excuse for a holiday.
But all of these volcanoes I've told you about are actually really weird...
Slide 7: Mid-ocean ridges
... because the over 80% of volcanic eruptions every year are along the system of mid-ocean ridges, which are mostly underwater. Brief explanation of plate tectonics.
Three types of volcanism: MOR, subduction zones, the Weird Stuff I've been telling you about.
And that pretty much covers the surface of the Earth, but...
Slide 8: How do we know what's inside the Earth?
We know that the Earth has an atmosphere, the crust, the mantle, and the core - it's layered (in roughly the same proportions as an apple!). The differences between these layers are what they're made out of.
So the first clue was orbit. The Earth goes round the Sun, and it does so at a particular distance taking a particular amount of time. We know what size it is. This means we can work out how much it must weigh - and it turns out that if you make the entire Earth out of the kind of rocks you see at the surface, it isn't heavy enough.
Sometimes, very rarely, we get to see bits of the mantle at the surface - closest to home, this is the case in Cornwall.
But that still leaves a lot of mass missing - the best way to explain it was iron and nickel, and this is in part because of...
Slide 9: Meteorites!
Meteorites formed at the same time as the rest of the solar system. There's lots of different types - some of them look like they are what would happen if you took the *entire solar system*, mushed it up, and took an average. So from those ones, we get a sense of how much iron there *should* be in the Earth... and there isn't enough in the crust or mantle.
But THEN we get meteorites that are very rich in iron, with some mantle-like material in them - that's the pallasite, on the left - and some that are *pure* iron-nickel. We think these come from meteorites that got big enough to differentiate, which the Earth managed - pallasites are super-rare (<1% of all meteorites found), and we think they're from the core-mantle boundary of meteorites that were like tiny planets. Iron-nickel meteorites, though, we think represent the *core* of these tiny planets. The really cool thing is that over time, they start to separate out (like if you mix oil and water - is this a good example...? cf salad dressing), so you get these patterns developing - and you can tell by the scale of the patterns how old the meteorite is.
I found this meteorite under my desk, and it's about the same age as the solar sytem: four point six billion years. Now, geologists have some pretty strange definitions, but even we think that's a long time.
Slide 10: what actually killed the dinosaurs
One thing that's pretty common knowledge about meteorites is that a giant one wiped out the dinosaurs. Actually, we're pretty sure it's a bit more complicated than that: at the same time as the meteorite hit (within a few million years... like I said, geologists have weird definitions), there was massive volcanism going on in India. Deccan Traps, flood basalts, dinosaur eggs interspersed between lava flows.
Slide 11: Geology as a science
Definition of the scientific method. Why geology is kind of a pity.
Slide 12: what words mean
... and this leads to us having some pretty strange ideas.
Slide 13: How many days in a year?
But even so we can tell all sorts of awesome stuff: like, how many days were there in a year 850 million years ago?
Stromatolites widely reckoned to be the oldest organism identified - earliest ones found at 3.5 billion years old. There are still some alive today in Australia. They're bacterial mats, and just like you can tell how old a tree is by counting its rings, you can count the rings in a stromatolite - one per year. But better than that, there are rings within rings - hundreds of tiny thin sheets. And the best we can tell is, because these bacteria are photosynthetic, those tiny thin sheets correspond to a single day. Modern stromatolites have 365 layers per ring... but fossils from 850 million years ago have 410. When the Earth was younger, it was still spinning faster on its axis - so days were shorter, and there were more of them in the time it took for the Earth to go once round the Sun!
Slide 14: Moons
But it's not just things about the Earth that we can tell - we can also work out stuff about the Moon. It helps to have had the lunar science missions, but even Darwin - who came up with the theory of evolution - was starting to think about how the Moon formed.
At the moment, we more or less think that it was another giant impact - something the size of Mars hit the Earth and knocked part of it off, which formed the Moon. There's still lots of argument about how exactly this all works - I went to a conference at the Royal Society in September, and I'm going to another one at the Natural History Museum in a month's time - but one of the ways that we work out when this happened is by looking at the cratering on the surface of the Moon.
[Meanwhile, Europa has plate tectonics based on ice.]
Slide 15: The bigger picture
... and that is really what it's all about: by studying the Earth - even just one volcano! - we can work out all sorts of stuff not only about how our planet and Moon formed, but about the solar system as a whole... and even further out.
And then I invite question.
In related news, I Will Never Leave This Basement Again, But Maybe I Am Finally Getting Data?
Slide 1: Inside (and outside) the Earth
I'm a volcanologist. This means I spend most of my time sat in a basement handling grey rock powder, but more importantly it means I have a list of my Top Five Favourite Volcanoes.
Slide 2: Mount Erebus, Antarctica
- permanent lava lake
- can see the plume of smoke rising from it - this helps us work out how pollution persists in the atmosphere
- it mostly goes "glop" very gently on a 20-minute cycle (like boiling a kettle) as hot lava rises up from the magma chamber and cold lava trickles back down, but sometimes it goes SPLORT on an 8-hour cycle
- you can see the chemical composition of the smoke plume changing over the course of this cycle!
- because it's hot, and there's ice, there's a whole bunch of ice caves around the mountain - and scientists go exploring in them
Slide 3: Ol Doinyo Lengai, Tanzania
- this literally erupts baking soda (rich in calcium, like in bones and milk; and in sodium, like in salt)
- most lava flows look black - but you see the white smear on the top? That isn't snow, it's lava
- the lava flows dissolve in rainwater and get washed into the lake, where the chemicals get used by aqueous bacteria to make the compounds that, when eaten, turn flamingoes pink
Slide 4: Mount Ngauruhoe, New Zealand
- featured as Mount Doom in the LotR films (you're probably too young for that because the first one came out when I was in year 7 oh dear)
- really pretty
- rich red colour comes from iron in the magmas that's rusting
- the black bits on the plain in the foreground? Those are lava flows, you can see how they spread out
Slide 5: Skaergaard, Greenland
Not an active volcano - but it's a fossil magma chamber. It's exciting because the magma chamber got filled up in one go, then was sealed off - so we can see how everything cooled down over thousands of years. One of the results is the beautiful layering you can see in the mountains - compare it to the size of the helicopter: it's huge! However, in order to do any useful work on it, you end up in dry camp in the middle of nowhere for most of a summer, and you have to carry rifles at all times in case of polar bears. (Will I give them nightmares if I tell them how to kill polar bears?)
Slide 6: Hawai'i
Hawai'i's really famous - it gives us the names of lots of types of lava, and it has absolutely beautiful fountaining eruptions. Also, Pacific Islanders have oral history about the goddess of the mountain, and how she fell out with her sister and they had an argument - and you can actually match these stories up to events we can identify from the different lava flows. Also, geologists try really hard to have their meetings there, as an excuse for a holiday.
But all of these volcanoes I've told you about are actually really weird...
Slide 7: Mid-ocean ridges
... because the over 80% of volcanic eruptions every year are along the system of mid-ocean ridges, which are mostly underwater. Brief explanation of plate tectonics.
Three types of volcanism: MOR, subduction zones, the Weird Stuff I've been telling you about.
And that pretty much covers the surface of the Earth, but...
Slide 8: How do we know what's inside the Earth?
We know that the Earth has an atmosphere, the crust, the mantle, and the core - it's layered (in roughly the same proportions as an apple!). The differences between these layers are what they're made out of.
So the first clue was orbit. The Earth goes round the Sun, and it does so at a particular distance taking a particular amount of time. We know what size it is. This means we can work out how much it must weigh - and it turns out that if you make the entire Earth out of the kind of rocks you see at the surface, it isn't heavy enough.
Sometimes, very rarely, we get to see bits of the mantle at the surface - closest to home, this is the case in Cornwall.
But that still leaves a lot of mass missing - the best way to explain it was iron and nickel, and this is in part because of...
Slide 9: Meteorites!
Meteorites formed at the same time as the rest of the solar system. There's lots of different types - some of them look like they are what would happen if you took the *entire solar system*, mushed it up, and took an average. So from those ones, we get a sense of how much iron there *should* be in the Earth... and there isn't enough in the crust or mantle.
But THEN we get meteorites that are very rich in iron, with some mantle-like material in them - that's the pallasite, on the left - and some that are *pure* iron-nickel. We think these come from meteorites that got big enough to differentiate, which the Earth managed - pallasites are super-rare (<1% of all meteorites found), and we think they're from the core-mantle boundary of meteorites that were like tiny planets. Iron-nickel meteorites, though, we think represent the *core* of these tiny planets. The really cool thing is that over time, they start to separate out (like if you mix oil and water - is this a good example...? cf salad dressing), so you get these patterns developing - and you can tell by the scale of the patterns how old the meteorite is.
I found this meteorite under my desk, and it's about the same age as the solar sytem: four point six billion years. Now, geologists have some pretty strange definitions, but even we think that's a long time.
Slide 10: what actually killed the dinosaurs
One thing that's pretty common knowledge about meteorites is that a giant one wiped out the dinosaurs. Actually, we're pretty sure it's a bit more complicated than that: at the same time as the meteorite hit (within a few million years... like I said, geologists have weird definitions), there was massive volcanism going on in India. Deccan Traps, flood basalts, dinosaur eggs interspersed between lava flows.
Slide 11: Geology as a science
Definition of the scientific method. Why geology is kind of a pity.
Slide 12: what words mean
... and this leads to us having some pretty strange ideas.
Slide 13: How many days in a year?
But even so we can tell all sorts of awesome stuff: like, how many days were there in a year 850 million years ago?
Stromatolites widely reckoned to be the oldest organism identified - earliest ones found at 3.5 billion years old. There are still some alive today in Australia. They're bacterial mats, and just like you can tell how old a tree is by counting its rings, you can count the rings in a stromatolite - one per year. But better than that, there are rings within rings - hundreds of tiny thin sheets. And the best we can tell is, because these bacteria are photosynthetic, those tiny thin sheets correspond to a single day. Modern stromatolites have 365 layers per ring... but fossils from 850 million years ago have 410. When the Earth was younger, it was still spinning faster on its axis - so days were shorter, and there were more of them in the time it took for the Earth to go once round the Sun!
Slide 14: Moons
But it's not just things about the Earth that we can tell - we can also work out stuff about the Moon. It helps to have had the lunar science missions, but even Darwin - who came up with the theory of evolution - was starting to think about how the Moon formed.
At the moment, we more or less think that it was another giant impact - something the size of Mars hit the Earth and knocked part of it off, which formed the Moon. There's still lots of argument about how exactly this all works - I went to a conference at the Royal Society in September, and I'm going to another one at the Natural History Museum in a month's time - but one of the ways that we work out when this happened is by looking at the cratering on the surface of the Moon.
[Meanwhile, Europa has plate tectonics based on ice.]
Slide 15: The bigger picture
... and that is really what it's all about: by studying the Earth - even just one volcano! - we can work out all sorts of stuff not only about how our planet and Moon formed, but about the solar system as a whole... and even further out.
And then I invite question.
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