1 00:00:02,040 --> 00:00:07,040 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, 2 00:00:07,080 --> 00:00:10,320 Speaker 1: Lauren Vogelbam. Here today we're talking about a rare but 3 00:00:10,440 --> 00:00:16,360 Speaker 1: incredibly deadly natural phenomenon, exploding lakes a k A. Limnic eruptions. 4 00:00:16,960 --> 00:00:19,759 Speaker 1: A limnic eruption is what happens when deadly gases like 5 00:00:19,840 --> 00:00:24,280 Speaker 1: carbon dioxide explode out of volcanic lakes. Sometimes the carnage 6 00:00:24,360 --> 00:00:28,360 Speaker 1: unfolds on multiple fronts. Just as lethal clouds suffocate humans 7 00:00:28,360 --> 00:00:31,240 Speaker 1: and animals, the abrupt displacement of water is liable to 8 00:00:31,240 --> 00:00:35,040 Speaker 1: create tsunamis. That exact combination of events killed more than 9 00:00:35,080 --> 00:00:38,720 Speaker 1: seventeen hundred people one grim summer day in nine six 10 00:00:38,760 --> 00:00:42,240 Speaker 1: in the West African country of Cameroon. And now scientists 11 00:00:42,280 --> 00:00:45,240 Speaker 1: wonder if an even bigger limnic eruption is in the making. 12 00:00:46,400 --> 00:00:49,479 Speaker 1: But how does such an explosion happen? Let's start with 13 00:00:49,560 --> 00:00:53,560 Speaker 1: water pressure. Water pressure increases with depth. That's why scuba 14 00:00:53,600 --> 00:00:56,000 Speaker 1: divers can't venture too far below the surface without the 15 00:00:56,040 --> 00:00:59,760 Speaker 1: right equipment. The force that's exerted upon a submerged object 16 00:00:59,800 --> 00:01:02,000 Speaker 1: by the weight of all the liquid above it is 17 00:01:02,000 --> 00:01:06,760 Speaker 1: called hydrostatic pressure. Normally, this pressure intensifies by fourteen point 18 00:01:06,800 --> 00:01:10,399 Speaker 1: five pounds per square inch or one kilo pascals or 19 00:01:10,480 --> 00:01:13,720 Speaker 1: one bar for every ten meters of water depth. That's 20 00:01:13,720 --> 00:01:17,640 Speaker 1: about thirty three ft. But the key to limnic eruptions 21 00:01:17,720 --> 00:01:21,720 Speaker 1: lies in temperature. The gases dissolve more easily in cold, 22 00:01:21,880 --> 00:01:25,360 Speaker 1: high pressure water. Limnic eruptions can only occur in deep 23 00:01:25,440 --> 00:01:28,200 Speaker 1: bodies of water with a lot of hydrostatic pressure at 24 00:01:28,240 --> 00:01:31,360 Speaker 1: the bottom. There must also be a significant difference in 25 00:01:31,400 --> 00:01:34,679 Speaker 1: both the pressure and temperature between the surface water and 26 00:01:34,720 --> 00:01:37,680 Speaker 1: the lower depths, With the lower depths being much chillier. 27 00:01:39,000 --> 00:01:42,800 Speaker 1: Stratification will act like a barrier, keeping that dissolved gas 28 00:01:42,840 --> 00:01:45,840 Speaker 1: confined to the lake bottom, where it can't depressurize and 29 00:01:46,000 --> 00:01:49,240 Speaker 1: escape out into the atmosphere. Because it's trapped, the dissolved 30 00:01:49,280 --> 00:01:53,760 Speaker 1: gas accumulates in massive and potentially deadly quantities. Explosions are 31 00:01:53,800 --> 00:01:56,880 Speaker 1: impossible in lakes whose lower and upper water levels intermingle 32 00:01:57,000 --> 00:02:00,480 Speaker 1: on the regular For build up to occur, the water 33 00:02:00,520 --> 00:02:03,919 Speaker 1: also needs a continuous supply of some highly soluble gas, 34 00:02:03,960 --> 00:02:08,040 Speaker 1: like carbon dioxide or methane, and that's where volcanism comes in. 35 00:02:08,560 --> 00:02:12,000 Speaker 1: At localities with active volcanoes, buried magma is liable to 36 00:02:12,040 --> 00:02:15,560 Speaker 1: send methane, CO two and other gases seeping up through 37 00:02:15,600 --> 00:02:18,799 Speaker 1: thin sections of Earth's crust. If a lake is overhead, 38 00:02:18,960 --> 00:02:21,600 Speaker 1: the gas may pass right into the water, traveling by 39 00:02:21,680 --> 00:02:25,200 Speaker 1: volcanic fence and other roots that brings us back to 40 00:02:25,280 --> 00:02:28,720 Speaker 1: Cameroon and to its lakes. NEOs and Monoun both are 41 00:02:28,760 --> 00:02:31,720 Speaker 1: located in a volcanic field, and both lake bottoms are 42 00:02:31,760 --> 00:02:36,080 Speaker 1: oversaturated with carbon dioxide, which underlying magma sends their way. 43 00:02:36,440 --> 00:02:40,200 Speaker 1: On August fifteenth, some of the deep water in Monoun 44 00:02:40,240 --> 00:02:42,679 Speaker 1: that had been loaded up with the dissolved gas ascended 45 00:02:42,720 --> 00:02:46,079 Speaker 1: to the surface. No one knows why this happened. It's 46 00:02:46,120 --> 00:02:49,960 Speaker 1: possible that heavy rainfall and an earthquake or landslide displaced 47 00:02:50,000 --> 00:02:53,560 Speaker 1: some of the lake bottom water. Regardless, as the water rose, 48 00:02:53,600 --> 00:02:57,200 Speaker 1: the dissolved carbon dioxide lurking inside it became depressurized and 49 00:02:57,240 --> 00:03:00,520 Speaker 1: formed bubbles. Those bubbles drove even more of the water 50 00:03:00,600 --> 00:03:02,960 Speaker 1: up to the top of the lake, resulting in a massive, 51 00:03:03,040 --> 00:03:07,040 Speaker 1: foul smelling cloud of carbon dioxide gas. Under the wrong 52 00:03:07,080 --> 00:03:10,360 Speaker 1: set of circumstances, this gas is extremely dangerous to people. 53 00:03:10,919 --> 00:03:13,320 Speaker 1: Large quantities of CEO to cling to the ground and 54 00:03:13,360 --> 00:03:16,720 Speaker 1: displace oxygen, which can lead to death by suffocation. The 55 00:03:16,840 --> 00:03:20,000 Speaker 1: eruption killed at least thirty seven people, and two years later, 56 00:03:20,120 --> 00:03:23,800 Speaker 1: on August twenty one, six, Lake Neo's experienced a limnic 57 00:03:23,919 --> 00:03:26,639 Speaker 1: eruption of its own. Once again, there was a sudden, 58 00:03:26,800 --> 00:03:30,520 Speaker 1: mysterious upheaval of carbon dioxide laden water from its frigid, 59 00:03:30,680 --> 00:03:33,959 Speaker 1: high pressure depths, but this time the body count was 60 00:03:34,040 --> 00:03:37,400 Speaker 1: much higher. Carbon dioxide from the Lake Neo's disaster killed 61 00:03:37,400 --> 00:03:40,640 Speaker 1: approximately one thousand, seven hundred forty six people and more 62 00:03:40,680 --> 00:03:43,960 Speaker 1: than three thousand, five hundred domestic animals. Somewhere from three 63 00:03:44,040 --> 00:03:47,040 Speaker 1: hundred thousand to one point six million metric tons of 64 00:03:47,080 --> 00:03:49,200 Speaker 1: c O two gas burst out of the water with 65 00:03:49,320 --> 00:03:51,920 Speaker 1: enough force to set off a twentys tsunami that's about 66 00:03:51,960 --> 00:03:56,440 Speaker 1: sixty six ft tall. That was the last recorded limnic eruption. 67 00:03:56,920 --> 00:03:59,280 Speaker 1: If you're worried about a killer limnic eruption coming to 68 00:03:59,280 --> 00:04:02,720 Speaker 1: a lake near you, University of Michigan geoscience professor yolks 69 00:04:02,920 --> 00:04:06,080 Speaker 1: Jung says you probably shouldn't be. Lake NEOs and Lake 70 00:04:06,120 --> 00:04:08,800 Speaker 1: Monoon are located just above the equator, where it tends 71 00:04:08,840 --> 00:04:11,000 Speaker 1: to be warm all year round, and there's just no 72 00:04:11,120 --> 00:04:13,440 Speaker 1: way for a limnic eruption to happen in a temperate 73 00:04:13,480 --> 00:04:17,320 Speaker 1: body of water. In places where seasonal temperatures vary widely, 74 00:04:17,520 --> 00:04:20,760 Speaker 1: like in the Great Lakes, lake surfaces often cool down, 75 00:04:21,080 --> 00:04:23,480 Speaker 1: causing the water at that level to sink and swap 76 00:04:23,520 --> 00:04:26,440 Speaker 1: places with the layers of water beneath it. Any gas 77 00:04:26,480 --> 00:04:29,120 Speaker 1: is dissolved in there don't stay trapped. They're released as 78 00:04:29,160 --> 00:04:34,640 Speaker 1: they depressurized nearer to the surface. No gas accumulation, no eruptions. However, 79 00:04:34,920 --> 00:04:37,200 Speaker 1: Young and many of his colleagues have taken a healthy 80 00:04:37,240 --> 00:04:40,520 Speaker 1: interest in Lake Kivu, an up and coming vacation destination 81 00:04:40,640 --> 00:04:43,240 Speaker 1: on the border of Rwanda and the Democratic Republic of 82 00:04:43,240 --> 00:04:46,840 Speaker 1: the Congo. Why because it seems to have all the 83 00:04:46,880 --> 00:04:51,720 Speaker 1: necessary criteria for a truly colossal limnic eruption. The lake 84 00:04:51,760 --> 00:04:54,880 Speaker 1: contains about ten point five billion cubic feet of carbon 85 00:04:54,920 --> 00:04:58,800 Speaker 1: dioxide that's about three billion cubic meters, and two billion 86 00:04:58,800 --> 00:05:01,520 Speaker 1: cubic feet of methane about up sixty billion cubic meters, 87 00:05:01,760 --> 00:05:05,480 Speaker 1: all lurking near the bottom. Were those gases to explode 88 00:05:05,520 --> 00:05:08,279 Speaker 1: from the lake's surface, the two million people who live 89 00:05:08,320 --> 00:05:13,200 Speaker 1: around Kivu might find themselves in jeopardy. One possible solution though, 90 00:05:13,720 --> 00:05:16,960 Speaker 1: harvest those very gases as a possible energy source by 91 00:05:16,960 --> 00:05:20,320 Speaker 1: an extraction barge. Kivu Wat is a one of a kind, 92 00:05:20,360 --> 00:05:23,760 Speaker 1: two million dollar facility that uses an offshore barge to 93 00:05:23,880 --> 00:05:26,480 Speaker 1: draw up water from the lake. It then siphons off 94 00:05:26,480 --> 00:05:28,799 Speaker 1: the methane and sends it to a power plant, generating 95 00:05:28,839 --> 00:05:31,800 Speaker 1: electricity for the area. When life gives you lemons, turn 96 00:05:31,880 --> 00:05:40,080 Speaker 1: it into electricity. Today's episode was written by Mark Mancini 97 00:05:40,120 --> 00:05:42,479 Speaker 1: and produced by Tyler Clang. For more on this and 98 00:05:42,520 --> 00:05:45,240 Speaker 1: lots of other powerful topics lurking in the depths, visit 99 00:05:45,240 --> 00:05:58,560 Speaker 1: our home planet has Stuff works dot com.