1 00:00:04,080 --> 00:00:09,040 This is geology bites with Oliver Strimple scattered around 2 00:00:09,040 --> 00:00:11,440 the globe. Within both oceanic and 3 00:00:11,440 --> 00:00:15,400 continental plates are some massive accumulations of igneous 4 00:00:15,400 --> 00:00:18,240 rocks called large igneous provinces. 5 00:00:19,160 --> 00:00:23,040 What causes such huge volumes of magma to flow onto the Earth's 6 00:00:23,040 --> 00:00:25,600 surface? And what impact does their 7 00:00:25,600 --> 00:00:29,160 emplacement have on the plates where they erupt, the atmosphere 8 00:00:29,160 --> 00:00:33,400 and climate and life? Richard Ernst has been studying 9 00:00:33,440 --> 00:00:36,240 all aspects of large Igneous provinces for nearly three 10 00:00:36,240 --> 00:00:39,320 decades and has written the definitive textbook on the 11 00:00:39,320 --> 00:00:42,240 subject. He is scientists in residence at 12 00:00:42,240 --> 00:00:46,640 Carlton University in Ottawa. Richard Ernst, Welcome to 13 00:00:46,640 --> 00:00:48,560 Geology Bites. Thank you, Oliver. 14 00:00:48,600 --> 00:00:51,600 It's great to be here. There are many places where 15 00:00:51,760 --> 00:00:55,400 volcanism has produced a lot of basalt on the surface of the 16 00:00:55,400 --> 00:00:59,280 Earth, not least from mid ocean spreading ridges and volcanic 17 00:00:59,280 --> 00:01:02,520 arks. Is there an accepted definition 18 00:01:02,640 --> 00:01:06,320 of a large anus province that distinguishes them from such 19 00:01:06,360 --> 00:01:11,120 other forms of volcanism? As originally defined in 1990, 20 00:01:11,240 --> 00:01:16,160 the basic aspect was a large volume intraplate event, 21 00:01:16,560 --> 00:01:20,440 typically with a short duration, and the minimum size was 22 00:01:20,440 --> 00:01:24,080 conceived as around 100,000 cubic kilometers. 23 00:01:24,680 --> 00:01:28,560 The intraplate setting distinguished from ordinary sea 24 00:01:28,560 --> 00:01:32,440 floor spreading and collisional related activities and they can 25 00:01:32,440 --> 00:01:36,360 be very very short duration, often times less than a million 26 00:01:36,360 --> 00:01:40,360 years, or can be multiple pulses over a longer period of time. 27 00:01:40,640 --> 00:01:44,360 But basically it's a bulk of extruded magma is where the 28 00:01:44,360 --> 00:01:47,360 definition lies, right? That's the main thing, that's 29 00:01:47,360 --> 00:01:50,000 how it's it was originally recognized it was these huge 30 00:01:50,000 --> 00:01:53,320 flood basalts observed in many parts of the world that could be 31 00:01:53,320 --> 00:01:57,280 kilometers thick of basaltic lava with very little interflow 32 00:01:57,280 --> 00:01:59,520 sediments. And so it was really recognized 33 00:01:59,520 --> 00:02:02,680 that these were kind of unique sort of thing and then they took 34 00:02:02,680 --> 00:02:06,480 this to the oceanic realm and recognized similar kind of thick 35 00:02:06,480 --> 00:02:09,240 accumulations of extrusive material. 36 00:02:09,440 --> 00:02:12,680 Can you describe the structure of a larger nears province? 37 00:02:13,080 --> 00:02:16,520 At the surface you could see the huge flood basalts that might be 38 00:02:16,520 --> 00:02:20,480 extensive over many many hundreds of kilometers, covering 39 00:02:20,560 --> 00:02:23,160 up to 1,000,000 or more square kilometers. 40 00:02:23,400 --> 00:02:26,280 But as the flood basalts are eroded, you see more of the 41 00:02:26,280 --> 00:02:29,800 plumbing system. You see giant radiating dike 42 00:02:29,800 --> 00:02:33,760 swarms that can have a radius of up to 2000 kilometers or more, 43 00:02:33,960 --> 00:02:38,040 giant circular swarms that could have a radius of almost 1000 44 00:02:38,040 --> 00:02:40,960 kilometers. Also you have massive sills, 45 00:02:40,960 --> 00:02:43,960 dolerite sill provinces associated with sedimentary 46 00:02:43,960 --> 00:02:46,520 basins. You also have the important 47 00:02:46,520 --> 00:02:50,320 group of Mavic ultromathic intrusive complexes that are 48 00:02:50,320 --> 00:02:52,320 also an important part of the plumbing system. 49 00:02:53,400 --> 00:02:56,840 And then as you go deeper, you get down to the magmatic under 50 00:02:56,840 --> 00:03:00,600 plate that's often present where you might have up to 10 million 51 00:03:00,600 --> 00:03:03,920 cubic kilometers or more of material created to the base of 52 00:03:03,920 --> 00:03:06,640 the crust as Mavic to ultromathic material. 53 00:03:07,000 --> 00:03:10,240 So the plumbing system is really quite extensive and this 54 00:03:10,280 --> 00:03:13,160 indicates that these events are really even more of a luminous 55 00:03:13,160 --> 00:03:15,920 than we realise from just looking at the extruded flood 56 00:03:15,920 --> 00:03:18,560 basalt. But if I was standing on top of 57 00:03:18,560 --> 00:03:22,840 a large Igneous province or on a continent to flood basalt, would 58 00:03:22,840 --> 00:03:26,480 I recognise it from the plumbing system or would I just see 59 00:03:26,480 --> 00:03:30,360 endless sheets or thick sheets of successive lava flows? 60 00:03:30,760 --> 00:03:32,280 Yeah, that's the way you would recognize it. 61 00:03:32,280 --> 00:03:35,280 You'd see yourself sitting on top of as far as the eye could 62 00:03:35,280 --> 00:03:37,560 see. Basaltic volcanism, Hawaiian 63 00:03:37,560 --> 00:03:39,560 style volcanism, but on steroids. 64 00:03:39,840 --> 00:03:43,240 If you have windows through it where the basalts were eroded, 65 00:03:43,240 --> 00:03:46,000 then you might see some of the dyke swarm component and the 66 00:03:46,000 --> 00:03:49,200 other plumbing system component. I have been to some of these 67 00:03:49,200 --> 00:03:52,040 large English provinces, for example on the western coast of 68 00:03:52,040 --> 00:03:54,360 Greenland and then also in the Deccan. 69 00:03:54,360 --> 00:03:57,960 And you can, when it's eroded through by a gully or something, 70 00:03:57,960 --> 00:04:02,440 just see layer upon layer upon layer upon layer, endless layers 71 00:04:02,440 --> 00:04:05,520 of successive lava flows. Yeah, dramatically so. 72 00:04:05,560 --> 00:04:08,600 And even in the ones that have been deeply eroded, like the 73 00:04:08,720 --> 00:04:12,160 McKenzie event of Northern Canada, where the dyke swarm 74 00:04:12,160 --> 00:04:15,800 component goes out to 2000 kilometers, in the focal region 75 00:04:15,800 --> 00:04:19,120 of this overall radiating swarm, you have the remnant of what 76 00:04:19,160 --> 00:04:22,240 must have been originally very, very extensive flood basalt 77 00:04:22,240 --> 00:04:25,640 sequence, the copper mine volcanics couple kilometers 78 00:04:25,640 --> 00:04:29,560 thick or so. What are the best known large 79 00:04:29,560 --> 00:04:32,280 igneous provinces? Where are they and roughly how 80 00:04:32,280 --> 00:04:35,960 many have been recognized? One of the most dramatic is the 81 00:04:35,960 --> 00:04:40,240 Siberian trapped large Igneous province, which extends over 82 00:04:40,240 --> 00:04:43,600 about 5,000,000 square kilometers in Siberia. 83 00:04:44,320 --> 00:04:49,160 Other hugely dramatic ones are the Central Atlantic Magmatic 84 00:04:49,160 --> 00:04:52,440 Province at 201 million years ago. 85 00:04:52,720 --> 00:04:55,400 So those are two well known ones. 86 00:04:55,400 --> 00:05:00,360 You mentioned the Deccan as well of India at 66,000,000 years. 87 00:05:00,720 --> 00:05:04,560 It is widespread in India. Those are the youngest ones and 88 00:05:04,560 --> 00:05:07,640 there's lots more young ones. But also as you go back through 89 00:05:07,640 --> 00:05:10,960 time and you look at the plumbing system component, we 90 00:05:10,960 --> 00:05:15,400 can trace them all the way back into the Archaean and up through 91 00:05:15,400 --> 00:05:18,680 the protozoic about 2 1/2 billion years ago. 92 00:05:18,840 --> 00:05:22,080 At the end of the Archaean we have them occurring every 20 or 93 00:05:22,080 --> 00:05:25,320 30 million years somewhere on the planet. 94 00:05:25,840 --> 00:05:29,640 And if you add in the oceanic plateaus which are only visible 95 00:05:29,640 --> 00:05:32,440 in the last 200 million years, while we still have current 96 00:05:32,440 --> 00:05:35,680 oceanic crust, but we know the oceanic plateau component 97 00:05:36,200 --> 00:05:40,000 continues back through time, we can see them as remnants in 98 00:05:40,000 --> 00:05:44,240 collisional zones of oceanic plateaus from closed oceans. 99 00:05:44,560 --> 00:05:49,040 And so we suspect that the rate of large in these provinces back 100 00:05:49,040 --> 00:05:53,840 through time might be as often as one every 15,000,000 years or 101 00:05:53,840 --> 00:05:56,760 so back through about 2, 1/2 billion years ago. 102 00:05:56,760 --> 00:06:00,680 And then in the Archaean, we're doing a new compilation based on 103 00:06:00,680 --> 00:06:03,760 all the new geocrinology etcetera and it's looking like 104 00:06:03,760 --> 00:06:06,440 the rate is going to be fairly similar. 105 00:06:06,920 --> 00:06:10,960 So you're saying really all the way back to the Archaean, We're 106 00:06:10,960 --> 00:06:15,200 talking about one of these being in place roughly every 107 00:06:15,200 --> 00:06:18,320 15,000,000 years? Potentially as often as and 108 00:06:18,320 --> 00:06:21,400 certainly every 20 to 30 million years based on the continental 109 00:06:21,400 --> 00:06:24,720 large Igneous Province record. But to my mind, we talk about 110 00:06:24,720 --> 00:06:28,320 plate tectonics a lot and it's a dominant mechanism on Earth. 111 00:06:28,360 --> 00:06:32,160 But this whole other process, this whole other voluminous 112 00:06:32,160 --> 00:06:36,080 magma production feature of Earth, is also incredibly 113 00:06:36,080 --> 00:06:38,360 important. Could you talk about the 114 00:06:38,840 --> 00:06:42,720 geochemical makeup? So being basaltic, we're talking 115 00:06:42,720 --> 00:06:47,600 fundamentally about Mayfair composition, but there's also, 116 00:06:47,600 --> 00:06:51,280 as I understand it, a variation between ultra mafic at the one 117 00:06:51,280 --> 00:06:54,960 end and also some fairly solicit components of these large 118 00:06:54,960 --> 00:06:57,880 Igneous provinces. That is certainly true for the 119 00:06:57,880 --> 00:07:02,360 continental examples, where it's mainly mafic with some ultra 120 00:07:02,360 --> 00:07:05,960 mafic component, but you can also have some more granitic 121 00:07:06,240 --> 00:07:10,480 compositions. As magma crystallizes, the 122 00:07:10,520 --> 00:07:13,920 residual liquid becomes more granitic through a fractionation 123 00:07:13,920 --> 00:07:17,360 of the magma. You can generate from the mapic 124 00:07:17,360 --> 00:07:19,800 magma some amounts of granitic type magma. 125 00:07:20,360 --> 00:07:24,360 But the other thing that is really fascinating component of 126 00:07:24,360 --> 00:07:27,760 continental large igneous provinces is the potential for 127 00:07:27,800 --> 00:07:31,480 the thermal source causing massive partial melting of the 128 00:07:31,480 --> 00:07:34,320 lower mapic crust. And if you melt a basaltic lower 129 00:07:34,320 --> 00:07:38,400 crust, you produce a granitic melt and so you can get massive 130 00:07:38,400 --> 00:07:42,240 provinces of granitic melt associated with large igneous 131 00:07:42,240 --> 00:07:45,000 provinces from the same heat source. 132 00:07:45,360 --> 00:07:48,520 But these massive provinces are interesting because they can 133 00:07:48,520 --> 00:07:52,560 have remarkable scale, 100,000 square kilometers or more. 134 00:07:52,760 --> 00:07:56,240 It's well known that you produce a lot of Brinitic type magnetism 135 00:07:56,240 --> 00:08:00,160 in collisional environments associated with subduction, and 136 00:08:00,160 --> 00:08:03,760 as you go back in time it can be hard to tell what setting you're 137 00:08:03,760 --> 00:08:05,680 in. And so when you have a large 138 00:08:05,840 --> 00:08:09,840 granitic magmatic province of some age, is it evidence of a 139 00:08:09,840 --> 00:08:13,360 plate tectonics collisional bone, or is it an example of a 140 00:08:13,360 --> 00:08:16,760 large igneous province producing solicit magnetism? 141 00:08:16,920 --> 00:08:18,600 Can you give an example of one of those? 142 00:08:18,880 --> 00:08:22,720 The Karu Large Igneous province, which is a massive event across 143 00:08:22,840 --> 00:08:26,960 southern Africa into Antarctica, and there's a felsic equivalent 144 00:08:26,960 --> 00:08:30,440 of it in southern South America. The Chon Ike event. 145 00:08:30,800 --> 00:08:34,120 How long does it take to form a particular larger province? 146 00:08:34,480 --> 00:08:39,120 Or to put it another way, do they have a typical magma 147 00:08:39,120 --> 00:08:42,600 extrusion rate? The geocronology on the Siberian 148 00:08:42,600 --> 00:08:47,240 Trap event indicate that this 5,000,000 cubic kilometer or 149 00:08:47,240 --> 00:08:51,360 more event, not including any under plate component which 150 00:08:51,360 --> 00:08:54,280 would probably make it much larger, all came out within less 151 00:08:54,280 --> 00:08:58,440 than a million years. The Central Atlantic Magmatic 152 00:08:58,440 --> 00:09:02,600 Province, which covers some 10 million square kilometers, 153 00:09:03,000 --> 00:09:06,320 Uranium lead dating suggests that most of it must have come 154 00:09:06,320 --> 00:09:10,600 out again within a million years or so, an incredibly short 155 00:09:10,600 --> 00:09:13,360 period. Where exactly is the Central 156 00:09:13,640 --> 00:09:15,680 Atlantic Magmatic Province today? 157 00:09:16,480 --> 00:09:20,360 The center of activity from the North American perspective in 158 00:09:20,360 --> 00:09:24,800 Florida, from the African perspective, it would be the 159 00:09:24,800 --> 00:09:27,160 corner of Africa. If you close the Atlantic Ocean, 160 00:09:27,320 --> 00:09:30,520 you tuck it in adjacent to Florida there and that's the 161 00:09:31,000 --> 00:09:33,240 center. But you have magnetism along the 162 00:09:33,240 --> 00:09:36,800 entire coast all the way up to Newfoundland on the Canadian 163 00:09:36,800 --> 00:09:39,320 side. It's also extensive down into 164 00:09:39,640 --> 00:09:43,920 Brazil, into the Amazon basin and then into West Africa, all 165 00:09:43,920 --> 00:09:49,120 the way up into Mauritania, Mali, up into Morocco, Algeria, 166 00:09:49,480 --> 00:09:52,000 up into Iberian Peninsula as well. 167 00:09:52,000 --> 00:09:55,440 So it's a massive event and everywhere we see it and dated 168 00:09:55,720 --> 00:10:00,720 it seems to have a 201 ± 1 or so million year age. 169 00:10:01,600 --> 00:10:05,600 However, there are also events that are coming out in multiple 170 00:10:05,600 --> 00:10:08,800 pulses that might span 10s of millions of years. 171 00:10:08,920 --> 00:10:12,200 One of the ones that's important is the North Atlantic large 172 00:10:12,200 --> 00:10:15,600 Igneous province which is on Greenland, the units in 173 00:10:15,600 --> 00:10:19,040 Greenland you were talking about and also in the UK and offshore 174 00:10:19,040 --> 00:10:21,520 as well. That North Atlantic Igneous 175 00:10:21,520 --> 00:10:27,160 province has a main pulse at 62 to 58,000,000 and then a second 176 00:10:27,160 --> 00:10:31,400 pulse with the onset of rifting in the North Atlantic at 55 And 177 00:10:31,480 --> 00:10:34,120 Iceland right in the middle of the North Atlantic which is 178 00:10:34,120 --> 00:10:38,960 active today, represents the continuation of the North 179 00:10:38,960 --> 00:10:43,320 Atlantic large Igneous province at a much lower volume and flux 180 00:10:43,320 --> 00:10:45,920 rate. What happens many times is you 181 00:10:45,920 --> 00:10:49,120 have these large Igneous provinces with a huge volume of 182 00:10:49,120 --> 00:10:52,720 magma in a short period of time, and then there's protracted 183 00:10:52,720 --> 00:10:57,320 magnetism at a much lower pace for another 100 to 200 million 184 00:10:57,320 --> 00:11:00,160 years. So Iceland has pulses at 60 185 00:11:00,160 --> 00:11:02,400 million years, then a second pulse of 55. 186 00:11:02,720 --> 00:11:06,440 Other events also have multiple pulses, oftentimes with the 187 00:11:06,440 --> 00:11:10,280 second pulse associated with the onset of rifting and continental 188 00:11:10,280 --> 00:11:12,880 breakup are. They unique to our planet. 189 00:11:13,560 --> 00:11:14,960 They are not unique to our planet. 190 00:11:15,360 --> 00:11:18,800 On Venus we see just a wealth of what we think of as large 191 00:11:18,800 --> 00:11:21,440 igneous provinces. On Venus, there's no plate 192 00:11:21,440 --> 00:11:23,360 tectonics. And so one of the things that's 193 00:11:23,360 --> 00:11:27,920 come from the study of huge flood basalt events, lava flows 194 00:11:27,920 --> 00:11:30,600 continuing for 1000 kilometers or more. 195 00:11:31,440 --> 00:11:35,320 We've also recently discovered huge dyke swarms on Venus. 196 00:11:35,520 --> 00:11:37,960 Venus has no erosion, no plate tectonics. 197 00:11:38,320 --> 00:11:41,400 Erosion is important because we see the surface expression of 198 00:11:41,400 --> 00:11:43,240 lava flows. We also see the surface 199 00:11:43,240 --> 00:11:47,160 expression of dykes laterally. We think of dykes moving up. 200 00:11:47,520 --> 00:11:51,000 They do, but they also can move sideways in the crust for long, 201 00:11:51,000 --> 00:11:53,480 long distances. We know that from Earth we see 202 00:11:53,480 --> 00:11:57,080 that demonstrated vividly on Venus, and we can trace them for 203 00:11:57,080 --> 00:12:02,320 long distances as swarms of dykes radiating for thousands of 204 00:12:02,320 --> 00:12:05,360 kilometers. We just recently traced a single 205 00:12:05,360 --> 00:12:09,520 one for almost 4000 kilometers, and because of the absence of 206 00:12:09,520 --> 00:12:14,480 plate tectonics, it really lends support to a mantle plume model. 207 00:12:15,320 --> 00:12:19,120 Let me also mention Mars. Mars has grabbing systems 208 00:12:19,120 --> 00:12:22,760 interpreted to be dyke storms 3 or 4000 kilometers long, 209 00:12:23,360 --> 00:12:28,720 associated with and radiating from this area of protracted 210 00:12:28,800 --> 00:12:32,560 plume related volcanism called the Tharsis region, and also on 211 00:12:32,560 --> 00:12:35,480 another region antipodally called the Elysium region. 212 00:12:35,960 --> 00:12:40,440 So there's boundless radiating grabbing systems on Mars that 213 00:12:40,440 --> 00:12:44,080 are also interpreted to represent huge, laterally in 214 00:12:44,080 --> 00:12:47,120 place, nathic dyke swarms associated with what we would 215 00:12:47,120 --> 00:12:49,000 call large igneous provinces on Earth. 216 00:12:49,720 --> 00:12:53,800 Let's talk about what might generate these prodigious 217 00:12:53,800 --> 00:12:56,480 volumes of lava that form these large igneous provinces. 218 00:12:56,480 --> 00:13:01,320 Then I understand that there are two categories of model, each of 219 00:13:01,320 --> 00:13:05,160 them providing A mechanism that generates anomalously hot mantle 220 00:13:05,160 --> 00:13:10,680 material at shallow levels. The first involves shallow, by 221 00:13:10,680 --> 00:13:15,360 which we mean crustal and upper mantle processes, and the 2nd 222 00:13:15,360 --> 00:13:20,080 invokes the deep mantle with the arrival of a hot mantle plume. 223 00:13:20,960 --> 00:13:23,000 Let's start with the former explanations. 224 00:13:23,800 --> 00:13:25,800 So there are a number of shallow mechanisms. 225 00:13:26,040 --> 00:13:30,080 The lithospheric portion of the surface plate can drop off and 226 00:13:30,080 --> 00:13:32,360 descend into the mantle. That's a process called 227 00:13:32,360 --> 00:13:35,760 delamination. And if so, then hotter material 228 00:13:35,760 --> 00:13:40,040 from the mantle below can rise to a shallower level and produce 229 00:13:40,040 --> 00:13:43,840 large volumes of melt. It's also been well recognized 230 00:13:43,840 --> 00:13:48,520 that rifting extension, as you thin the the plate, then you 231 00:13:48,520 --> 00:13:52,240 also bring hotter mantle material to a shallower level 232 00:13:52,760 --> 00:13:55,240 and it can then also cause partial melting. 233 00:13:56,040 --> 00:13:59,400 There's another class of shallow models that also sort of things 234 00:13:59,400 --> 00:14:02,360 to a supercontinent cycle. We know that the continents come 235 00:14:02,360 --> 00:14:05,200 together and break apart and come together and that's 236 00:14:05,200 --> 00:14:08,080 happened several times in Earth history, the most recent time 237 00:14:08,440 --> 00:14:12,280 being Pangaea that was together over the last few 100 million 238 00:14:12,280 --> 00:14:15,480 years and started to break apart around 200 million years ago. 239 00:14:16,040 --> 00:14:18,640 When you assemble all these cottons together, there's a 240 00:14:18,640 --> 00:14:24,360 region of mantle that is covered by thicker crust, grenaded 241 00:14:24,360 --> 00:14:26,920 crust, and it represents some sort of thermal blanket. 242 00:14:26,920 --> 00:14:29,760 So the temperature can then build up in the mantle 243 00:14:29,760 --> 00:14:33,040 underneath then potentially enough to generate melting. 244 00:14:33,600 --> 00:14:37,720 I'm reminded of the episode of Georgie Bites that we did with 245 00:14:37,920 --> 00:14:41,160 Peter Molnar, where he talked about the foundering of an 246 00:14:41,160 --> 00:14:45,720 anchor below Tibet as an explanation of why it's so high 247 00:14:45,720 --> 00:14:47,680 today. And I think that is what you're 248 00:14:47,680 --> 00:14:52,400 referring to by delamination of the lithosphere in a a heavier 249 00:14:52,960 --> 00:14:56,040 portion below sinking into the sinospheric mantle below. 250 00:14:56,800 --> 00:15:01,240 And similarly, Damien Nance also talked about the thermal 251 00:15:01,240 --> 00:15:05,320 blanketing just at the last episode of ways in which you 252 00:15:05,320 --> 00:15:08,560 could get extra heating that would then lead to the demise of 253 00:15:08,560 --> 00:15:11,440 a supercontinent. So let's talk about the second 254 00:15:11,520 --> 00:15:15,280 category of model, namely the ones that involve the deep 255 00:15:15,280 --> 00:15:19,680 mantle and the mantle plume. You have a plume that rises, and 256 00:15:19,680 --> 00:15:23,760 the top of the plume is growing as it rises because it is being 257 00:15:23,760 --> 00:15:27,160 filled from below faster than it can push its way up through the 258 00:15:27,160 --> 00:15:29,920 mantle. And so the size of the plume 259 00:15:29,920 --> 00:15:32,040 head is predictable by the modeling. 260 00:15:32,040 --> 00:15:35,000 And you get a plume head at the top that's many hundreds of 261 00:15:35,000 --> 00:15:39,520 kilometers across and flattens when it reaches the base of the 262 00:15:39,520 --> 00:15:42,800 plate to something potentially 2000 kilometers across. 263 00:15:43,360 --> 00:15:47,120 And this kind of arrival and flattening can take place within 264 00:15:47,120 --> 00:15:51,560 a very short time, meaning that you suddenly get into a zone 265 00:15:51,560 --> 00:15:55,800 where massive melting happens very, very quickly, leading to 266 00:15:55,800 --> 00:15:58,800 large India's provinces in providing an explanation for 267 00:15:59,240 --> 00:16:02,480 very rapid generation of huge volumes of melt. 268 00:16:03,160 --> 00:16:06,800 So this mantle plume idea has also been useful for us with 269 00:16:06,800 --> 00:16:11,840 respect to radiating dyke swarms we see in the McKenzie swarm, 270 00:16:11,840 --> 00:16:13,680 which is one of the most magnificent in the world. 271 00:16:13,720 --> 00:16:16,960 It extends out over 2000 kilometers in radius. 272 00:16:17,240 --> 00:16:19,960 Where is that located? In northern Canada, so it 273 00:16:19,960 --> 00:16:22,920 continues from northern Canada, the Arctic coast all the way 274 00:16:22,920 --> 00:16:25,720 down, not too far from Lake Superior. 275 00:16:26,080 --> 00:16:29,560 The radiating swarms, the kind of thing you get from domal 276 00:16:29,560 --> 00:16:33,240 uplift above a mantle plume. A plume lifts up the crust a 277 00:16:33,240 --> 00:16:37,880 kilometer or so and produces radio fractures that are filled 278 00:16:37,880 --> 00:16:41,280 by magma from the plume and you get a radio swarm. 279 00:16:41,680 --> 00:16:45,640 The swarm and the McKenzie and the swarm of many others is 280 00:16:45,640 --> 00:16:49,200 radio for a distance and then swings beyond a certain distance 281 00:16:49,200 --> 00:16:52,320 influenced by some sort of regional stress sterile to the 282 00:16:52,320 --> 00:16:55,000 plume. And we take that transition as a 283 00:16:55,000 --> 00:16:57,480 measure of the size of the underlying plumes. 284 00:16:57,800 --> 00:17:00,880 So in the case of the McKenzie, it transitioned from radiating 285 00:17:01,040 --> 00:17:04,480 to a swinging into another regional stress pattern beyond 286 00:17:04,560 --> 00:17:07,520 at about 1000 kilometers consistent with this mantle 287 00:17:07,520 --> 00:17:10,880 plume modeling. Do these various models also 288 00:17:10,880 --> 00:17:13,440 help explain what we see on Mars and Venus then? 289 00:17:14,160 --> 00:17:16,960 Indeed they do. On Venus, I mentioned this 290 00:17:17,119 --> 00:17:19,760 nearly 4000 kilometer long individual dike. 291 00:17:19,760 --> 00:17:24,520 It radiates away from a big volcanic center, radiates out 292 00:17:24,680 --> 00:17:29,480 1200 kilometers, and then swings about 50° into a trend that's 293 00:17:29,480 --> 00:17:33,200 parallel to a rift zone that's 10,000 kilometers long. 294 00:17:33,680 --> 00:17:37,600 So we have a dramatic change in trend right at 1200 kilometers, 295 00:17:37,920 --> 00:17:41,520 consistent with hundreds of other dikes that we are seeing 296 00:17:41,520 --> 00:17:44,280 as part of the radiating system. But this particular individual 297 00:17:44,280 --> 00:17:49,000 dike shows it so dramatically. On Mars, we see beautiful 298 00:17:49,000 --> 00:17:52,360 radiating swarms that seem to go out three or 4000 kilometers, 299 00:17:52,680 --> 00:17:56,600 and the entire Tharsis Rise is larger than 5000 kilometers 300 00:17:56,600 --> 00:17:58,640 across. So it's a big event on its own. 301 00:17:59,120 --> 00:18:03,080 How does the model explain the initial radial pattern? 302 00:18:03,160 --> 00:18:06,200 And then there's a certain radius, the swinging out there 303 00:18:06,200 --> 00:18:09,040 dykes. In order to drive a dyke out 304 00:18:09,120 --> 00:18:11,240 laterally for that part, you have to have a lot of magma. 305 00:18:11,240 --> 00:18:13,880 So you have to have magma continually being pumped into 306 00:18:14,280 --> 00:18:18,080 the starting end of the dyke. The source area for Dike Magnus 307 00:18:18,080 --> 00:18:20,080 is typically near the plume center. 308 00:18:20,200 --> 00:18:22,840 So within a few 100 kilometers of the plume center, we can see 309 00:18:22,840 --> 00:18:27,320 in some cases gravity anomalies marking intrusions from which 310 00:18:27,320 --> 00:18:30,600 the dikes were pumped out. And they're pumped out initially 311 00:18:30,600 --> 00:18:34,280 in the direction given by the Domal uplift, which imposes the 312 00:18:34,280 --> 00:18:38,520 stress on the crust that favors radiating openings. 313 00:18:39,040 --> 00:18:41,960 And so the magma that's being pumped outward from the center 314 00:18:41,960 --> 00:18:45,760 region takes advantage of these preferred opening directions and 315 00:18:45,760 --> 00:18:50,280 happily drives out laterally and keeps driving out sideways. 316 00:18:50,320 --> 00:18:54,400 And then if it gets beyond the plume head, there is still 317 00:18:54,400 --> 00:18:56,920 regional stress. On Earth, it's related to plate 318 00:18:56,920 --> 00:19:00,720 boundary stresses. In continental areas away from 319 00:19:00,880 --> 00:19:04,000 spreading zones or collisional zones, there's intraplate 320 00:19:04,000 --> 00:19:06,240 stresses that have preferred directions. 321 00:19:07,160 --> 00:19:10,520 And so the idea is that the magma keeps being pumped into 322 00:19:10,520 --> 00:19:12,960 the starting end of the dike, and the magma keeps moving at 323 00:19:12,960 --> 00:19:15,320 the far end. And once it gets beyond the 324 00:19:15,320 --> 00:19:18,120 domal uplift, beyond the influence of the stresses 325 00:19:18,120 --> 00:19:22,080 related to the uplifting plume head, the magma still wants to 326 00:19:22,080 --> 00:19:24,000 go. And it's going to happily go in 327 00:19:24,000 --> 00:19:27,000 the direction of whatever the stress it experiences at that 328 00:19:27,000 --> 00:19:28,600 point. And on Earth is presumably 329 00:19:28,600 --> 00:19:32,560 related to some sort of plate boundary or collisional 330 00:19:32,800 --> 00:19:36,080 subduction stresses. On Venus we see this one that 331 00:19:36,200 --> 00:19:40,560 parallels this huge rift zone for 2000 kilometres of it's 332 00:19:40,720 --> 00:19:43,680 10,000 kilometres long, full length of that Rift Zone. 333 00:19:44,480 --> 00:19:48,080 As we look through the geological record, we often see 334 00:19:48,080 --> 00:19:51,560 a temporal coincidence between the emplacement of a large ignis 335 00:19:51,560 --> 00:19:54,440 province and continental rifting. 336 00:19:55,400 --> 00:19:58,960 Can you give some examples of this and do we understand why 337 00:19:58,960 --> 00:20:03,360 this is so? We clearly see many examples 338 00:20:03,360 --> 00:20:07,800 where a rival of a large Igneous province is associated with 339 00:20:07,960 --> 00:20:12,160 attempted breakup and often successful breakup to open a new 340 00:20:12,160 --> 00:20:14,440 ocean. On one hand, you have the 341 00:20:14,440 --> 00:20:18,480 Central Atlantic Magmatic Province at 201 million years, 342 00:20:18,480 --> 00:20:23,360 which precedes the opening of the Atlantic by 5/10/15 million 343 00:20:23,360 --> 00:20:25,400 years. Beautiful correlation there. 344 00:20:25,720 --> 00:20:29,520 On the other hand you have the magnificent Siberian Traps, 345 00:20:29,720 --> 00:20:34,280 Archignis Province, which did try to break up Siberia from 346 00:20:34,280 --> 00:20:36,920 Europe. The West of Siberia has major 347 00:20:36,920 --> 00:20:40,120 rift zones that are part of the Siberian Trap event and 348 00:20:40,120 --> 00:20:42,880 represent serious attempted breakup, but ultimately 349 00:20:42,880 --> 00:20:45,880 unsuccessful. So this points out that there's 350 00:20:45,880 --> 00:20:50,200 two aspects that are relevant. You have to have favorables, 351 00:20:50,200 --> 00:20:53,880 plate boundary stresses in order for there to be successful. 352 00:20:53,880 --> 00:20:57,360 In the case of the Central Atlantic, there was already a 353 00:20:57,360 --> 00:21:01,040 whole series of rift basins, at least on the North American 354 00:21:01,040 --> 00:21:05,600 side, called the Newark series of basins that represented NS 355 00:21:05,600 --> 00:21:09,480 rifting prior to the ultimate breakup. 356 00:21:09,480 --> 00:21:13,440 That happened 30 or 40 million years later after the arrival of 357 00:21:13,440 --> 00:21:16,400 the central magnetic province. So in that case, you'd say there 358 00:21:16,400 --> 00:21:19,240 was favorable plate boundary stresses, they were already 359 00:21:19,240 --> 00:21:22,280 interested in causing a breakup, and then the mantle plume 360 00:21:22,280 --> 00:21:27,520 arrives, causes some uplift, causes radiating dikes from, but 361 00:21:27,520 --> 00:21:31,120 also causes potential triple junction rifting in multiple 362 00:21:31,120 --> 00:21:35,120 directions, going north to separate North America from 363 00:21:35,240 --> 00:21:39,040 Europe and Africa into the South to move South America away. 364 00:21:39,800 --> 00:21:43,200 Ore deposits are linked to large igneous provinces. 365 00:21:43,960 --> 00:21:47,560 What kind of ores are these, and do we understand what the 366 00:21:47,560 --> 00:21:50,600 connection is? Yes, we have some good ideas. 367 00:21:50,880 --> 00:21:54,840 Most ores for copper, nickel and platinum group elements, 368 00:21:54,840 --> 00:21:56,600 platinum and Palladium in particular. 369 00:21:57,160 --> 00:22:01,520 They are genetically associated with large igneous provinces, 370 00:22:02,120 --> 00:22:07,240 and part of the story has to be with the kind of magma you get 371 00:22:07,240 --> 00:22:11,120 both mafic and ultra mafic magnetisms in large igneous 372 00:22:11,120 --> 00:22:14,840 provinces. Ultra mafic magnetism can often 373 00:22:14,840 --> 00:22:17,800 be associated with elevated levels of some of these elements 374 00:22:17,800 --> 00:22:20,720 that then can get concentrated in a layered intrusion. 375 00:22:20,720 --> 00:22:24,800 For instance, like the Bushfeld intrusion in Southern Africa, a 376 00:22:24,800 --> 00:22:27,400 huge reservoir of many rich ore deposits. 377 00:22:27,400 --> 00:22:31,400 It's a single body that extends 400 kilometers across and maybe 378 00:22:31,400 --> 00:22:34,680 7 kilometers thick. A huge body of magma that 379 00:22:34,680 --> 00:22:38,680 differentiates and produces significant ore deposits at 380 00:22:38,680 --> 00:22:41,440 different levels. And it's part of a large Igneous 381 00:22:41,440 --> 00:22:44,080 province that a little over 2 billion years ago in southern 382 00:22:44,080 --> 00:22:47,520 Africa. Then the real magmatic sulphide 383 00:22:47,520 --> 00:22:50,000 deposits in the Siberian trap event. 384 00:22:50,480 --> 00:22:54,560 Those seem to have interacted with silicon rich units at some 385 00:22:54,560 --> 00:22:59,160 point, causing sulphur saturation and production of a 386 00:22:59,160 --> 00:23:02,560 separate magmatic sulphide liquid that can interact with 387 00:23:02,760 --> 00:23:06,520 the huge volumes of magma that might be moving by it in a magma 388 00:23:06,520 --> 00:23:09,240 chamber. The idea is if you have a 389 00:23:09,240 --> 00:23:13,880 separate liquid adjacent to the basaltic liquid, as the basaltic 390 00:23:13,880 --> 00:23:17,320 liquid is moving by it, it's sulfur loving elements like 391 00:23:17,320 --> 00:23:20,480 nickel and copper and platinum group elements jump out of the 392 00:23:20,480 --> 00:23:25,200 basaltic magma and jump into the sulfide magma and progressively 393 00:23:25,200 --> 00:23:27,480 get more and more rich in the magmatic sulfide. 394 00:23:27,480 --> 00:23:30,000 And that's part of the reason then that large in these 395 00:23:30,000 --> 00:23:32,560 provinces are important in magmatic sulfides because they 396 00:23:32,560 --> 00:23:36,600 have a potential for huge volumes of magma to move by 397 00:23:36,920 --> 00:23:39,640 magmatic sulfides and continually offer them the 398 00:23:39,640 --> 00:23:43,240 opportunity to get more and more enriched in the sulfur loving 399 00:23:43,520 --> 00:23:46,880 elements, nickel, copper and PGS that are very important in the 400 00:23:46,880 --> 00:23:51,520 Green Revolution. We also see a correlation 401 00:23:51,880 --> 00:23:55,760 between the emplacement of a large Igneous province and a 402 00:23:55,760 --> 00:23:59,440 major mass extinction. Can you give examples of these 403 00:23:59,520 --> 00:24:03,080 and how do we think this comes about? 404 00:24:03,480 --> 00:24:06,880 Yeah, the best perhaps is the Siberian Trap event that I 405 00:24:06,880 --> 00:24:10,240 mentioned before, which covers Northern Siberia and Central 406 00:24:10,240 --> 00:24:12,960 Siberia. All of it seems to be in place 407 00:24:13,040 --> 00:24:17,160 within less than a million years and precisely within a short 408 00:24:17,160 --> 00:24:22,520 time both preceding and post dating the well dated timing of 409 00:24:22,520 --> 00:24:24,400 the Permo Triassic mass extinction. 410 00:24:24,480 --> 00:24:28,240 So that's a superb example. I mentioned the Central Atlantic 411 00:24:28,240 --> 00:24:30,680 Magmatic Province, two O 1,000,000 years. 412 00:24:30,840 --> 00:24:34,120 It precisely brackets the Triassic, Jurassic mass 413 00:24:34,120 --> 00:24:37,200 extinction. The Deccan event marching this 414 00:24:37,200 --> 00:24:41,400 province in India. Again, most of it is less than a 415 00:24:41,400 --> 00:24:43,360 million years. It does seem to have two or 416 00:24:43,360 --> 00:24:46,800 three distinct pulses, very short duration for the main 417 00:24:46,800 --> 00:24:51,360 pulse, again bracketing in time the mass extinction associated 418 00:24:51,360 --> 00:24:53,120 with the demise of the dinosaurs. 419 00:24:53,400 --> 00:24:56,960 In that particular case, the dating on the chick cha Lube 420 00:24:56,960 --> 00:25:00,040 meteorite impact in the Yucatan peninsula seems to give a 421 00:25:00,040 --> 00:25:04,000 similar age, and so it looks like it's a joint effort between 422 00:25:04,240 --> 00:25:07,520 a large igneous province and a meteorite impact in that case, 423 00:25:07,520 --> 00:25:11,560 and causing that extinction. I presume the extinctions are 424 00:25:11,560 --> 00:25:14,840 thought to be a consequence of the global environmental impacts 425 00:25:14,840 --> 00:25:18,600 of these enormous eruptions that create these larger Guinness 426 00:25:18,600 --> 00:25:22,320 provinces. But what exactly is so inimical 427 00:25:22,320 --> 00:25:24,720 to life? There's a bounty of riches in 428 00:25:24,720 --> 00:25:27,440 that regard. There's rapid global warming, 429 00:25:27,720 --> 00:25:33,720 1520° temperature increases above present and acid rain can 430 00:25:33,720 --> 00:25:36,600 be an important component. The Siberian Traps event 431 00:25:36,680 --> 00:25:41,040 modeling shows that there's CO2 and SO2 sulfur dioxide coming 432 00:25:41,040 --> 00:25:44,120 out, but there's also the thermogenetic gases. 433 00:25:44,120 --> 00:25:46,760 So this huge amount of gas release from sills, the 434 00:25:46,760 --> 00:25:50,240 intrusive component interacting with sediments and in the case 435 00:25:50,240 --> 00:25:52,440 Siberian trap. There's the opportunity to 436 00:25:52,440 --> 00:25:55,400 interact with hydrocarbons with oil deposits. 437 00:25:55,640 --> 00:25:58,920 Also an opportunity to interact with evaporate sedimentary 438 00:25:58,920 --> 00:26:01,640 deposits you get in deserts from evaporation of water. 439 00:26:02,080 --> 00:26:05,560 They heated up some evaporates of sediments to see what would 440 00:26:05,560 --> 00:26:11,440 be released from SIL at 1000° being adjacent to such sediments 441 00:26:11,880 --> 00:26:14,320 and they would release chlorine and bromine compounds. 442 00:26:14,320 --> 00:26:17,320 So those are ozone destroying. So the ozone destroying is also 443 00:26:17,320 --> 00:26:20,640 a possibility. Mercury releases well poisonous 444 00:26:20,640 --> 00:26:23,160 mercury. It seems that mercury levels are 445 00:26:23,160 --> 00:26:26,000 higher from large against province events, so they are a 446 00:26:26,000 --> 00:26:28,200 source of mercury poisoning potentially. 447 00:26:29,040 --> 00:26:34,360 Paradoxically, you can also have remarkable cooling episodes that 448 00:26:34,360 --> 00:26:36,400 are associated with large ING this provinces. 449 00:26:36,560 --> 00:26:39,600 If you erupt a large ING this province at the equator, there's 450 00:26:39,600 --> 00:26:42,960 a lot of flood basalts and then they can be rapidly eroded 451 00:26:42,960 --> 00:26:46,720 within a million years or so, and that sucks a lot of CO2 of 452 00:26:46,720 --> 00:26:49,080 the atmosphere. So if you're in a cooler 453 00:26:49,200 --> 00:26:52,360 transition time, it's enough to potentially pull you into a 454 00:26:52,360 --> 00:26:55,840 snowball Earth where the oceans are frozen to the equator. 455 00:26:56,760 --> 00:27:01,240 And an example of that is the longest snowball Earth in this 456 00:27:01,240 --> 00:27:05,720 Earth's history from about 719,000,000 to 660,000,000 years 457 00:27:05,720 --> 00:27:08,360 ago, so-called sturtine glaciation. 458 00:27:09,040 --> 00:27:12,000 And what occurred right at the absolute beginning of that? 459 00:27:12,560 --> 00:27:15,760 The huge Largigius province in Canada, known as the Franklin 460 00:27:15,760 --> 00:27:18,560 Largigius Province, 2 or 3,000,000 square kilometers in 461 00:27:18,560 --> 00:27:23,520 Canada, whose precise ages 719 like a million years before the 462 00:27:23,520 --> 00:27:25,520 onset of the sturtine glaciation. 463 00:27:26,600 --> 00:27:29,720 And yet there's more. We have the same age event in 464 00:27:29,720 --> 00:27:33,040 formerly attached Siberia called the Irkutsk Largeignius 465 00:27:33,040 --> 00:27:37,200 Province, and there's more. We have at the same time in the 466 00:27:37,760 --> 00:27:41,160 portion of southern Africa and probably into adjacent 467 00:27:41,160 --> 00:27:45,040 Antarctica, another largeignius province called the Mutari 468 00:27:45,040 --> 00:27:50,240 Fingerin that's of the same age. And also in South China there's 469 00:27:50,240 --> 00:27:54,400 a Largeignius province of the same age, and probably in 470 00:27:54,400 --> 00:27:57,320 Northern Europe. In Baltica there's another a 471 00:27:57,320 --> 00:27:58,920 large igneous province of the same age. 472 00:27:59,280 --> 00:28:02,680 Some of these other ones are also at the equator, so the 473 00:28:02,680 --> 00:28:07,160 causing of the Grand 13 Glaciation Snowball Earth event 474 00:28:07,960 --> 00:28:11,280 due to a large Igneous province, almost certainly the Franklin 475 00:28:11,280 --> 00:28:15,560 Large Igneous Province was the cause and in a time where it was 476 00:28:15,560 --> 00:28:17,880 already cooling down. It's interesting that for some 477 00:28:17,880 --> 00:28:20,320 of these you eject a ton of greenhouse gases into the 478 00:28:20,320 --> 00:28:23,880 atmosphere and you Jack up the temperature by 1020°. 479 00:28:24,480 --> 00:28:28,080 Yet for others it's the subsequent effect of the 480 00:28:28,120 --> 00:28:32,400 drawdown of CO2 from all the erosion leading to cooling that 481 00:28:32,400 --> 00:28:35,840 is the major effect. I suppose it's a question of 482 00:28:35,840 --> 00:28:39,240 different time scales. It's a little more complicated 483 00:28:39,240 --> 00:28:42,880 than that because you also have sulfur dioxide release and so 484 00:28:42,880 --> 00:28:46,880 that's initially greenhouse warming, but it can also convert 485 00:28:46,880 --> 00:28:50,640 to a sulfate very rapidly and become solar blocking. 486 00:28:50,960 --> 00:28:55,600 So you have the CO2 pulse initially from the gas, both 487 00:28:55,600 --> 00:28:59,440 from the volcanics and from the heating up by seals of adjacent 488 00:28:59,440 --> 00:29:02,400 sediments. The sulfur dioxide component, if 489 00:29:02,400 --> 00:29:05,880 it's large, takes you from an initial warming and start some 490 00:29:05,880 --> 00:29:09,680 cooling. And then if you rapidly remove 491 00:29:09,680 --> 00:29:14,360 and erode the the salts at an equator, you more than 492 00:29:14,360 --> 00:29:17,560 compensate for whatever CO2 you put into the atmosphere and you 493 00:29:17,560 --> 00:29:21,040 have a net loss. So you would expect a little bit 494 00:29:21,040 --> 00:29:24,200 of a pulse of warming right at the beginning to sulfite 495 00:29:24,200 --> 00:29:27,760 aerosol, slight transition, then to some cooling and then if the 496 00:29:27,760 --> 00:29:31,360 erosions kicks in then it can be even more dramatic cooling. 497 00:29:31,720 --> 00:29:35,120 If three or four coincident Lodgingness provinces triggered 498 00:29:35,120 --> 00:29:38,680 the Sturtian glaciation in the near Protrozoic, what about the 499 00:29:38,680 --> 00:29:42,000 Marin Owens Snowball episode that came soon after the end of 500 00:29:42,000 --> 00:29:45,240 the Sturtian? There's some candidates both for 501 00:29:45,760 --> 00:29:49,600 the interruption between the Sturti and the Marinolan that 502 00:29:49,600 --> 00:29:53,040 you have pump a lot of CO2 in the atmosphere and that may have 503 00:29:53,040 --> 00:29:55,880 temporarily taken us out of the Sturti and and then there's 504 00:29:55,880 --> 00:29:59,160 another candidate at the end of the Marinolan for potentially 505 00:29:59,160 --> 00:30:02,520 ending that period. And then there's also the gas 506 00:30:02,520 --> 00:30:06,680 gear's glaciation at 580 or so, which seems to be very short and 507 00:30:06,680 --> 00:30:10,160 it may have been both started and ended by a large ignis 508 00:30:10,160 --> 00:30:14,240 problem, started by a basaltic large ignis component and ended 509 00:30:14,240 --> 00:30:17,160 by the felsa component. Can I mention one of the things 510 00:30:17,160 --> 00:30:22,640 is we have this wild idea that Venus had a massive climate 511 00:30:22,640 --> 00:30:27,160 change from earlier habitable conditions to its modern 512 00:30:27,160 --> 00:30:30,360 climate, with no plate tectonics and no erosion. 513 00:30:30,760 --> 00:30:34,440 Could multiple large igneous provinces happening at the same 514 00:30:34,440 --> 00:30:38,840 time on Venus, each of them increasing the global 515 00:30:38,840 --> 00:30:43,200 temperature by 10 or 15°? Say have 3 superimposed. 516 00:30:43,480 --> 00:30:47,720 You can increase the global temperature by 45° and that 517 00:30:47,720 --> 00:30:52,160 would lead to runaway ocean evaporation and lead to the end 518 00:30:52,160 --> 00:30:55,040 of plate tectonics. Water is considered important 519 00:30:55,040 --> 00:30:59,800 for subduction to continue, so we propose that this great 520 00:30:59,800 --> 00:31:03,760 climate transition from Earth like conditions on Venus to the 521 00:31:03,760 --> 00:31:10,200 current 450°C self cleaning oven type temperatures was initiated 522 00:31:10,200 --> 00:31:13,800 through multiple large igneous provinces happening at the same 523 00:31:13,800 --> 00:31:15,880 time. And we have cheekily said 524 00:31:16,480 --> 00:31:18,720 perhaps this is an Earth's distant future. 525 00:31:18,800 --> 00:31:21,640 There's nothing to stop a similar mechanism from happening 526 00:31:21,640 --> 00:31:23,160 hundreds of millions of years from now. 527 00:31:24,520 --> 00:31:26,520 Richard Anst, thank you very much. 528 00:31:26,840 --> 00:31:30,040 Thanks so much, Oliver. To see pictures and 529 00:31:30,040 --> 00:31:35,480 illustrations that support this podcast, go to geologybytes.com, 530 00:31:36,000 --> 00:31:39,320 where you'll also find transcripts and a subject matter 531 00:31:39,320 --> 00:31:43,280 index of all the episodes there. You can also give me feedback, 532 00:31:43,280 --> 00:31:47,080 which I welcome, as well as sign up to get my emails about new 533 00:31:47,080 --> 00:31:47,800 episodes.