WEBVTT - The Very Dust, Part 5 0:00:03.080 --> 0:00:07.080 Welcome to Stuff to Blow Your Mind, the production of iHeartRadio. 0:00:13.080 --> 0:00:15.040 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:15.080 --> 0:00:16.000 is Robert Lamb. 0:00:16.160 --> 0:00:18.479 And I am Joe McCormick, and we're back with the 0:00:18.680 --> 0:00:22.720 fifth and final part in our series on dust. This 0:00:22.760 --> 0:00:25.079 has really been an epic saga, taking it to five 0:00:25.200 --> 0:00:28.320 full parts in the series. We usually say that if 0:00:28.360 --> 0:00:30.800 you you know, if you haven't heard the previous parts 0:00:30.800 --> 0:00:32.320 in the series, you should go back and listen to 0:00:32.360 --> 0:00:34.960 those first so you get the flow. But honestly, I 0:00:35.040 --> 0:00:37.239 think this series is a little bit less narrative in 0:00:37.280 --> 0:00:39.120 format than some of the other ones we've done, So 0:00:39.159 --> 0:00:41.040 if you start with this one, I don't think it 0:00:41.080 --> 0:00:42.080 makes a huge difference. 0:00:42.120 --> 0:00:44.000 I mean, don't get too cocky, don't do them in 0:00:44.280 --> 0:00:47.400 exact reverse order. I think that would be a little strange. 0:00:47.440 --> 0:00:49.919 But you know, maybe you don't have to be as 0:00:49.920 --> 0:00:51.320 careful about it, right. 0:00:51.400 --> 0:00:53.960 So, but a very brief review. In part one, we 0:00:54.040 --> 0:00:57.800 talked about how to define dust. We talked about pyroglyphic 0:00:57.920 --> 0:01:00.800 dust mites which live in our homes and our furniture 0:01:01.240 --> 0:01:06.120 and eating our sleft off skin flakes delicious. We talked 0:01:06.120 --> 0:01:10.759 about the relationship between atmospheric dust and climate. In Part two, 0:01:10.840 --> 0:01:14.080 we talked about dust bunnies inner and outer, including dust 0:01:14.120 --> 0:01:18.280 bunnies in space, and we talked about how historical attitudes 0:01:18.319 --> 0:01:22.880 toward dust had changed over time, changing ideas in hygiene 0:01:22.959 --> 0:01:26.920 and things like that affecting interior design in the nineteenth century. 0:01:27.920 --> 0:01:30.000 In Part three, we talked about the role of dust 0:01:30.000 --> 0:01:33.720 in urban Victorian London and in the novel Dracula, and 0:01:33.760 --> 0:01:36.920 we also talked about the Sororietys paradox also known as 0:01:36.959 --> 0:01:41.440 the paradox of the heap, using dust accumulation as an example. 0:01:41.840 --> 0:01:45.640 And in Part four we talked mostly about select examples 0:01:45.680 --> 0:01:50.360 of dust having interesting significance in myths, rituals, and beliefs 0:01:50.360 --> 0:01:53.280 about magic and alchemy. And now we're back for more. 0:01:53.400 --> 0:01:56.000 So I think in the final episode of this series 0:01:56.440 --> 0:02:00.560 we are going to focus primarily on dust storms. 0:02:01.360 --> 0:02:03.720 That's right into the dust storm. 0:02:04.080 --> 0:02:07.080 So we've talked about how one of the defining features 0:02:07.120 --> 0:02:11.000 of dust is its tendency to fly, the tendency of 0:02:11.080 --> 0:02:14.200 dust particles to be borne aloft on the wind and 0:02:14.639 --> 0:02:17.160 float in the air for long periods of time, and 0:02:17.240 --> 0:02:20.239 for very small particles, this can be true even when 0:02:20.360 --> 0:02:22.959 air currents are fairly gentle, you know, it doesn't take 0:02:23.040 --> 0:02:25.720 more than a like a you know, fan in the 0:02:25.720 --> 0:02:29.880 house or somebody walking by to send some dust flying. However, 0:02:29.960 --> 0:02:34.519 if conditions are right, when winds become stronger, even particles 0:02:34.639 --> 0:02:38.480 larger than the normal flying dust threshold can be picked 0:02:38.520 --> 0:02:41.679 up and carried in the air, and this can result 0:02:41.720 --> 0:02:46.839 in dust storms, also known sometimes as sandstorms, also known 0:02:46.960 --> 0:02:50.160 in some instances as a haboob, which is a term 0:02:50.200 --> 0:02:53.560 that comes from from Arabic and sort of refers to 0:02:53.600 --> 0:02:57.280 a particular type of dust storm. For some people, especially 0:02:57.360 --> 0:03:00.400 people in very arid climates, dust storms might just be 0:03:00.440 --> 0:03:02.520 a regular part of life, you know, a thing that 0:03:02.560 --> 0:03:05.200 you get used to, especially in certain seasons of the year. 0:03:05.919 --> 0:03:08.560 But if you're unfamiliar with them, or if you are 0:03:08.680 --> 0:03:13.359 experiencing a dust storm at the extremes of size and intensity, 0:03:14.280 --> 0:03:18.640 dust storms can be frightening, all inspiring natural events, turning 0:03:18.680 --> 0:03:23.079 up massive, surging clouds of dust and soil so powerful 0:03:23.120 --> 0:03:27.400 I've seen them described as land based tsunamis that once 0:03:27.440 --> 0:03:29.920 they envelop you can blot out the sun and cause 0:03:29.960 --> 0:03:34.320 a kind of midnight at noon. And to illustrate what 0:03:34.560 --> 0:03:39.120 a dust storm at the extreme of intensity and the 0:03:39.160 --> 0:03:42.520 surprise factor can be like. I just wanted to mention 0:03:42.760 --> 0:03:46.760 a couple of descriptions of and facts about a particular 0:03:46.840 --> 0:03:50.440 dust storm that hit the Great Planes of the United 0:03:50.440 --> 0:03:53.960 States on April fourteenth, nineteen thirty five. This is a 0:03:54.040 --> 0:03:56.920 day that came to be known as Black Sunday, named 0:03:56.920 --> 0:04:01.800 after the storm, and with historical perspective, this particular storm 0:04:01.840 --> 0:04:04.880 on April fourteenth came to be seen as part of 0:04:04.920 --> 0:04:07.840 a larger pattern of drought and dust storms in the 0:04:07.880 --> 0:04:10.600 prairies of the central United States that stretched throughout the 0:04:10.680 --> 0:04:13.680 nineteen thirties and is known as the dust Bowl. And 0:04:13.800 --> 0:04:17.400 dust storms were very frequent during the dust Bowl. But 0:04:17.520 --> 0:04:20.800 the US National Weather Service actually has a great information 0:04:20.960 --> 0:04:24.679 page on the Black Sunday storm which collects some quotes 0:04:24.720 --> 0:04:29.600 from eyewitnesses and contemporary news reports, and they are fascinating 0:04:29.680 --> 0:04:33.359 and harrowing. So this storm was very large. It swept 0:04:33.360 --> 0:04:36.360 across multiple states through the middle of the United States, 0:04:36.360 --> 0:04:40.159 but it seems that the panhandles of Texas and Oklahoma 0:04:40.680 --> 0:04:44.240 got the worst of the effects. The storm in this 0:04:44.279 --> 0:04:47.600 region sort of began in mid afternoon around four PM 0:04:48.160 --> 0:04:51.320 and stretched on into the evening and according to the 0:04:51.440 --> 0:04:55.239 National Weather Service summary, in some places winds reached sixty 0:04:55.279 --> 0:04:58.040 miles per hour, and in certain parts of the storm 0:04:58.080 --> 0:04:59.920 it was as dark as night or even. 0:05:01.320 --> 0:05:01.480 So. 0:05:01.760 --> 0:05:04.599 I want to read a couple of these contemporary descriptions 0:05:04.839 --> 0:05:08.400 that have been collected here. One is from a newspaper 0:05:08.400 --> 0:05:12.600 called the Liberal News. This is from April nineteen thirty five. 0:05:13.080 --> 0:05:15.479 I believe this is the newspaper of a town in 0:05:15.560 --> 0:05:18.920 Kansas called Liberal. It's the name of the town. It says, 0:05:19.000 --> 0:05:22.719 a great black bank rolled in out of the northeast, 0:05:23.040 --> 0:05:26.840 and in a twinkling when it struck, Liberal plunged everything 0:05:26.880 --> 0:05:31.000 into inky blackness, worse than that on any midnight when 0:05:31.040 --> 0:05:34.359 there is at least some starlight and outlines of objects 0:05:34.360 --> 0:05:37.800 can be seen. When the storm struck, it was impossible 0:05:37.839 --> 0:05:41.680 to see one's hand before his face, even two inches away, 0:05:42.040 --> 0:05:44.800 and it was several minutes before any trace of daylight 0:05:44.920 --> 0:05:49.080 whatsoever returned. Then I got another passage. This is written 0:05:49.080 --> 0:05:53.360 by someone named Pauline Winkler Gray, writing a piece called 0:05:53.360 --> 0:05:57.000 the Black Sunday of April fourteenth, nineteen thirty five for 0:05:57.160 --> 0:06:01.599 the Kansas Historical Society. This author right, it was as 0:06:01.640 --> 0:06:06.240 though the sky was divided into two opposite worlds. On 0:06:06.320 --> 0:06:10.279 the south, there was blue sky, golden sunlight, and tranquility. 0:06:10.760 --> 0:06:13.880 On the north, there was a menacing curtain of boiling 0:06:14.000 --> 0:06:17.080 black dust that appeared to reach a thousand or more 0:06:17.120 --> 0:06:19.760 feet into the air. It had the appearance of a 0:06:19.800 --> 0:06:23.840 mammoth waterfall in reverse color as well as form. The 0:06:23.880 --> 0:06:27.200 apex of the cloud was plumed and curling, seething and 0:06:27.240 --> 0:06:32.400 tumbling over itself from north to south, and whipping trash, papers, sticks, 0:06:32.440 --> 0:06:36.320 and cardboard cartons before it. Even the birds were helpless 0:06:36.360 --> 0:06:39.839 in the turbulent onslaught and dipped and dived without the 0:06:39.880 --> 0:06:43.240 benefit of wings as the wind propelled them. As the 0:06:43.279 --> 0:06:46.159 wall of dust and sand struck our house, the sun 0:06:46.279 --> 0:06:50.800 was instantly blotted out completely. Gravel particles clattered against the 0:06:50.800 --> 0:06:54.240 windows and pounded down on the roof. The floor shook 0:06:54.279 --> 0:06:57.840 with the impact of the wind, and the rafters creaked threateningly. 0:06:58.320 --> 0:07:01.240 We stood in our living room in pitch blackness. We 0:07:01.240 --> 0:07:04.720 were stunned. Never had we been in such all enveloping 0:07:04.800 --> 0:07:07.799 blackness before, such impenetrable gloom. 0:07:08.320 --> 0:07:08.839 Oh wow. 0:07:09.400 --> 0:07:11.840 And another source I wanted to mention a couple of 0:07:12.040 --> 0:07:14.520 details from this is the book that I brought it 0:07:14.640 --> 0:07:16.680 brought up in Part one of the podcast series. It's 0:07:16.680 --> 0:07:18.880 a book called Dust to the Modern World in a 0:07:18.920 --> 0:07:23.440 Trillion Particles by Jay Owens, published twenty twenty three. This 0:07:23.440 --> 0:07:26.480 book has a chapter which talks about dust storms, drought, 0:07:26.520 --> 0:07:30.080 and the dust bowl, and the author here relates an 0:07:30.120 --> 0:07:33.640 eyewitness telling by a woman named Ada Kerns talking to 0:07:33.720 --> 0:07:37.240 the Oklahoma Historical Society about Black Sunday many years later, 0:07:37.960 --> 0:07:41.600 and she claims that she's listening to the radio and 0:07:41.640 --> 0:07:44.600 suddenly the radio announcer had to cut in and say 0:07:44.600 --> 0:07:48.560 we're going off the air, and gave no explanation why, so, 0:07:49.240 --> 0:07:52.720 Owens writes about this quote, no time to say why. 0:07:52.880 --> 0:07:55.800 The storm carried so much static electricity that it was 0:07:55.840 --> 0:07:59.920 shorting out electrical equipment and car engines. Barbed wire fence 0:08:00.200 --> 0:08:04.320 is visibly glowed with charge. The storm front rolled southward, 0:08:04.360 --> 0:08:07.160 picking up more dirt and power as it went. The 0:08:07.200 --> 0:08:10.600 sky filled with birds racing ahead, The ground ran with 0:08:10.720 --> 0:08:14.560 jack rabbits. The dust storm rolled along the horizon, inexorable 0:08:14.640 --> 0:08:17.200 and terrifying, a wall of oblivion. 0:08:18.080 --> 0:08:18.480 Wow. 0:08:18.800 --> 0:08:21.560 She also quotes multiple people who she kind. 0:08:21.400 --> 0:08:23.520 Of observes that there's like this. 0:08:23.560 --> 0:08:27.600 Trend of different people, all saying they had the same 0:08:27.720 --> 0:08:30.520 thought when they saw the dust storm approaching, which is 0:08:30.560 --> 0:08:33.000 that they thought the world was ending, or at least 0:08:33.080 --> 0:08:35.240 in an expressive way, said it was like the world 0:08:35.360 --> 0:08:37.880 was ending in fact, JJ, if you want to pull 0:08:37.880 --> 0:08:40.480 in a little bit of media. Apparently, Woody Guthrie has 0:08:40.520 --> 0:08:43.960 a song that was possibly inspired by this event. The 0:08:43.960 --> 0:08:46.720 song is known as Dusty Old Dust or so long 0:08:46.800 --> 0:08:49.360 It's been Good to know you and has some lyrics 0:08:49.360 --> 0:08:53.199 about dust storms that I'm gonna say, I love Woody Guthrie. 0:08:53.720 --> 0:08:57.000 This song, the vibes of it do not quite convey 0:08:57.120 --> 0:08:59.640 the terror and intensity of these quotes. 0:09:00.120 --> 0:09:04.280 Oh long it's been good denoy you? This dusty old 0:09:04.480 --> 0:09:07.520 Dust is a blowing me. Yeah. Yeah, I mean they're 0:09:07.520 --> 0:09:09.760 just looking at the lyrics of the song. I mean, yeah, 0:09:09.760 --> 0:09:14.040 there's talking about the sun being blocked out and people saying, 0:09:14.400 --> 0:09:18.000 so long it's been good to know yet. But yeah, 0:09:18.040 --> 0:09:21.000 maybe that's not completely conveyed in the overall tone of 0:09:21.040 --> 0:09:21.360 the song. 0:09:21.800 --> 0:09:23.240 It's a friendly sounding melody. 0:09:23.320 --> 0:09:24.800 Yeah. 0:09:24.840 --> 0:09:27.000 So again for some people around the world, people who 0:09:27.040 --> 0:09:30.439 live especially in desert regions or arid or semi arid 0:09:30.480 --> 0:09:33.720 regions where dust storms are common, it might not seem 0:09:33.760 --> 0:09:35.760 as all inspiring, maybe in the same way that if 0:09:35.800 --> 0:09:38.040 you'd never seen a regular, you know, a thunderstorm with 0:09:38.160 --> 0:09:40.480 lightning and rain before, if you saw that, it would 0:09:40.480 --> 0:09:43.600 seem truly terrifying and all inspiring. So I, you know, 0:09:43.840 --> 0:09:46.400 we get used to the large scale weather and natural 0:09:46.400 --> 0:09:50.360 phenomena that happen often in our surroundings. But if you 0:09:50.440 --> 0:09:52.520 are not used to the idea of a dust storm, 0:09:52.880 --> 0:09:57.199 as I certainly am not, it seems just an overwhelming experience. 0:09:57.720 --> 0:10:00.000 So Rob I did attach a few photos we can 0:10:00.080 --> 0:10:04.319 look at that managed to in various contexts capture the 0:10:04.400 --> 0:10:07.720 dust wall boundary like of an advancing dust storm, and 0:10:07.800 --> 0:10:10.360 it looks just shocking, you know. There's like it's like 0:10:11.120 --> 0:10:15.480 mountainous dark clouds just pouring over the land. 0:10:16.240 --> 0:10:21.480 Yeah. Absolutely, I have relatives that live out in Arizona, 0:10:21.600 --> 0:10:25.440 and I've never been out there during a dust storm. 0:10:25.800 --> 0:10:28.760 I've been driving through Arizona or parts of New Mexico 0:10:28.800 --> 0:10:31.040 where they have the signs beware dust storm and even 0:10:31.080 --> 0:10:34.080 like instructions on what to do, namely like pull over 0:10:34.200 --> 0:10:37.360 that sort of thing. But I'd asked them about it, 0:10:37.440 --> 0:10:39.880 you know, I asked my relatives there and you know, 0:10:39.920 --> 0:10:41.920 what was it like and so forth, and ended up 0:10:41.920 --> 0:10:44.680 looking up. If you just do an image search for 0:10:44.800 --> 0:10:48.080 dust storms A Z, you'll get some pretty tremendous looking 0:10:48.360 --> 0:10:51.160 images and some footage as well. And yeah, there's just 0:10:51.200 --> 0:10:54.280 a very apocalyptic appearance to these things, just a massive 0:10:54.360 --> 0:10:58.559 wall of dust rolling in, you know, blotting out the sun, 0:10:58.760 --> 0:11:02.640 turning the world red or gray in the shadows. I'm 0:11:02.640 --> 0:11:06.320 glad I've not had the experience firsthand. I'm sure we 0:11:06.400 --> 0:11:09.160 have listeners out there who have been through these many times, 0:11:09.200 --> 0:11:12.000 and perhaps you can write in and share your experiences 0:11:12.000 --> 0:11:12.320 with us. 0:11:12.920 --> 0:11:13.480 Please do. 0:11:23.440 --> 0:11:23.640 Rob. 0:11:23.640 --> 0:11:26.719 I'm glad you mentioned the idea of pulling over if 0:11:26.720 --> 0:11:28.440 you're on the road and there's a dust storm, because 0:11:28.440 --> 0:11:30.679 it does seem based on what I've read, that one 0:11:30.679 --> 0:11:33.320 of the biggest hazards actually of a dust storm is 0:11:33.320 --> 0:11:35.679 not so much that the storm is going to harm 0:11:35.760 --> 0:11:40.520 you directly, but it's the reduction in visibility and the 0:11:40.520 --> 0:11:43.760 way that it can affect like machines and electronics. So 0:11:44.440 --> 0:11:47.120 you don't want to be trying to fly or drive 0:11:47.280 --> 0:11:49.440 in the middle of a dust storm that you can 0:11:49.480 --> 0:11:53.160 have collisions in an aircraft or ground based vehicle. It's 0:11:53.200 --> 0:11:56.120 just better to avoid it, obviously if you're flying, but 0:11:56.400 --> 0:11:58.199 if you're in a car stop, you know you don't 0:11:58.200 --> 0:12:00.640 want to be trying to weave your way through the 0:12:00.720 --> 0:12:01.520 darkness at noon. 0:12:02.000 --> 0:12:04.960 Yeah, I believe the general advice and do check your 0:12:05.000 --> 0:12:06.719 local signs. Just take my word for it here, but 0:12:06.760 --> 0:12:08.800 I believe you're supposed to, like, you know, turn off 0:12:08.840 --> 0:12:12.160 your engine, turn off your lights, put your vehicle in park, 0:12:12.200 --> 0:12:15.040 and so forth. So yeah, the signs are very clear 0:12:15.040 --> 0:12:17.800 about this in areas where dust storms are a possibility. 0:12:18.240 --> 0:12:22.040 However, this does raise interesting questions because I certainly look 0:12:22.040 --> 0:12:24.080 at a dust storm and think I've never seen anything 0:12:24.160 --> 0:12:26.640 like this firsthand. I would just be overwhelmed by it. 0:12:27.080 --> 0:12:29.360 But then I think, why is it that I've never 0:12:29.400 --> 0:12:32.040 seen anything like this firsthand? Why is it that they 0:12:32.080 --> 0:12:35.360 only occur in some regions and not in others. To 0:12:35.400 --> 0:12:38.360 some people, dust storms or a regular seasonal thing, you 0:12:38.440 --> 0:12:40.280 just get used to it. You prepare for it. You 0:12:40.320 --> 0:12:42.560 try to rely on weather prediction as far as that'll 0:12:42.559 --> 0:12:45.120 help you prepare for it. You know, you can put 0:12:45.160 --> 0:12:48.640 tarps over things, and you can take measures to try 0:12:48.679 --> 0:12:51.160 to avoid getting in trouble in a dust storm. But 0:12:51.240 --> 0:12:52.960 for lots of people around the world. It's just a 0:12:52.960 --> 0:12:55.320 regular part of life. So why don't we get major 0:12:55.400 --> 0:12:58.040 dust storms around where we live? It has to do 0:12:58.240 --> 0:13:00.560 with climate. So this is going to raise general questions 0:13:00.600 --> 0:13:03.719 about how do dust storms work, what actually causes them, 0:13:03.760 --> 0:13:06.160 and where do they form. So I was looking at 0:13:06.240 --> 0:13:09.160 a number of sources on this question, and a really 0:13:09.200 --> 0:13:10.840 good one I came across is what do you know? 0:13:10.880 --> 0:13:14.600 A good old house stuff Works article by Vicky Jugo, 0:13:15.880 --> 0:13:18.160 Rob and I. If you're newer to the show, never 0:13:18.160 --> 0:13:20.120 heard us talk about this before. Robin I used to 0:13:20.160 --> 0:13:23.080 work for How Stuff Works. Seeing still see the stuff 0:13:23.080 --> 0:13:24.839 and the title of the podcast there. 0:13:25.000 --> 0:13:28.319 Yep, yep, still have some bylines on that website. 0:13:28.520 --> 0:13:30.600 Well, anyway, I learned a lot of things about dust 0:13:30.640 --> 0:13:32.880 storms from this house Stuff Works article, so it's a 0:13:32.880 --> 0:13:36.640 pretty good one. So dust storms can occur anywhere where 0:13:36.679 --> 0:13:39.200 the conditions are right, but they are especially common in 0:13:39.280 --> 0:13:44.160 certain places around the world, places in arid regions of 0:13:44.160 --> 0:13:49.240 Central Africa, in Australia, in Central Asia, and arid parts 0:13:49.240 --> 0:13:53.479 of North America. And why is it in these locations 0:13:53.520 --> 0:13:56.040 in particular that dust storms are the most common. It's 0:13:56.080 --> 0:13:59.240 local climate conditions, as you might expect it. Dust storms 0:13:59.280 --> 0:14:02.560 are most like in places where the top soil is 0:14:02.679 --> 0:14:07.920 loose and dry, so places where the ground is wet 0:14:08.200 --> 0:14:11.560 or where the soil is firmly crusted together are going 0:14:11.559 --> 0:14:14.400 to release fewer particles into the air when the wind 0:14:14.480 --> 0:14:18.120 kicks up, so obviously less likely to create a dust storm. 0:14:18.880 --> 0:14:22.440 These conditions of dry, loose top soil are most common 0:14:22.560 --> 0:14:27.640 in arid regions, especially after a period of drought. In fact, 0:14:27.720 --> 0:14:32.320 water helps protect the soil from erosion in multiple ways. 0:14:32.440 --> 0:14:37.280 It directly physically helps bind the soil by getting it 0:14:37.320 --> 0:14:40.520 wet and making it compact, you know, helping it clump together. 0:14:41.440 --> 0:14:45.520 But it also nourishes plant life, and the plants in 0:14:45.520 --> 0:14:49.640 turn help protect against soil erosion in many ways. So 0:14:49.800 --> 0:14:52.840 plants help bind soil and hold it in place with 0:14:52.880 --> 0:14:56.240 their roots, but plants can also serve as wind breaks 0:14:56.280 --> 0:14:58.760 which slow down the wind that might blow away the 0:14:58.800 --> 0:15:02.480 top soil. Can also help prevent water from washing away 0:15:02.600 --> 0:15:06.160 soil when rain does fall, so dust storms are most 0:15:06.240 --> 0:15:10.080 common in deserts and semi arid lands. You can think 0:15:10.120 --> 0:15:13.160 of dryness and drought as triggering a kind of vicious 0:15:13.200 --> 0:15:16.960 cycle of loss of plant life and subsequent soil erosion, 0:15:17.240 --> 0:15:21.440 and soil erosion can give rise to dust storms. The 0:15:21.480 --> 0:15:24.840 process by which fertile and semi arid land is gradually 0:15:24.840 --> 0:15:29.600 degraded into full desert is known as desertification, and the 0:15:29.640 --> 0:15:33.480 house Stuffworks article here mentions one particularly notable case of 0:15:34.040 --> 0:15:38.760 relatively recent natural desertification. Because there's some desertification that's caused 0:15:38.760 --> 0:15:41.680 by human land use practices, certain types of agriculture and 0:15:41.720 --> 0:15:45.680 stuff like that, but there's also natural desertification, just as 0:15:46.040 --> 0:15:49.000 the climate of regions changes over time. And the natural 0:15:49.040 --> 0:15:51.840 example mentioned in this article is a place called the 0:15:51.960 --> 0:15:56.840 Badeleai Depression. So the Badeleai Depression is a sandy dry 0:15:56.960 --> 0:16:00.520 basin at the southern edge of the Sahara Desert, centered 0:16:00.600 --> 0:16:03.880 in the northern half of the country of Chad. Today 0:16:04.000 --> 0:16:07.560 it's a relatively low lying desert region, but about seven 0:16:07.600 --> 0:16:11.120 thousand years ago it was the location of a vast 0:16:11.360 --> 0:16:16.880 freshwater lake known to scientists as Lake mega Chad. Lake 0:16:16.960 --> 0:16:20.280 Megachad covered more than four hundred thousand square kilometers, which 0:16:20.320 --> 0:16:22.440 is larger than all of the Great Lakes of North 0:16:22.440 --> 0:16:23.520 America put together. 0:16:24.240 --> 0:16:24.960 That's a big lake. 0:16:25.280 --> 0:16:26.160 That's a Mega Chad. 0:16:26.240 --> 0:16:26.760 Yeah. 0:16:27.440 --> 0:16:30.640 But as the climate of the Sahara region changed, the 0:16:30.720 --> 0:16:34.560 lake dried up and left behind the Baudela depression, and 0:16:34.760 --> 0:16:38.080 this region today is especially important as a source of 0:16:38.280 --> 0:16:43.400 atmospheric dust. A study by Elan Korn and others in 0:16:43.440 --> 0:16:47.680 two thousand and six found that during the winter, zero 0:16:47.720 --> 0:16:51.440 point seven tons of dust from this dry lake bed 0:16:51.480 --> 0:16:54.400 alone is blown up into the atmosphere every single day. 0:16:55.000 --> 0:16:56.640 So I got a little bit interested in this, and 0:16:56.720 --> 0:16:59.880 I found a paper by Washington at All published in 0:17:00.040 --> 0:17:02.560 Proceedings to the National Academy of Sciences in two thousand 0:17:02.560 --> 0:17:05.600 and nine called dust as a tipping element the Bdella 0:17:05.720 --> 0:17:11.200 depression chad and this paper suggested that the Badelea depression, 0:17:11.359 --> 0:17:14.080 this one single area is the source of about half 0:17:14.240 --> 0:17:17.960 of the mineral aerosols that come from the whole Sahara desert, 0:17:18.480 --> 0:17:22.120 and these mineral aerosols and dust from the Sahara more 0:17:22.160 --> 0:17:27.199 generally are very important for spreading supplemental mineral nutrients to 0:17:27.240 --> 0:17:29.840 the Amazon region. You may have read or seen about 0:17:29.840 --> 0:17:33.879 this before, that there's a cross oceanic current of dust 0:17:33.960 --> 0:17:37.400 through the atmosphere where this dust is lifted up off 0:17:37.400 --> 0:17:40.120 of the Sahara goes across the desert some goes into 0:17:40.160 --> 0:17:43.320 the Caribbean basin. I think some goes into the Amazon, 0:17:43.520 --> 0:17:46.399 and the nutrients that are in this dust are very 0:17:46.440 --> 0:17:49.439 important for sustaining the Amazon rainforest. 0:17:50.119 --> 0:17:52.000 Again kind of getting back into some of what we 0:17:52.040 --> 0:17:55.359 talked about earlier in the series about the connection between 0:17:55.440 --> 0:17:57.720 dust and weather and climate. 0:17:58.359 --> 0:18:02.080 Right, So, why so much dust coming off of this area. Well, 0:18:02.320 --> 0:18:04.760 apparently part of the reason is that there's sort of 0:18:04.960 --> 0:18:08.320 a wind gauntlet that feeds into it. I was reading 0:18:08.359 --> 0:18:12.440 a piece about this by the NASA Earth Observatory which 0:18:12.440 --> 0:18:15.280 writes that, quote, mountain ranges to the northeast of the 0:18:15.280 --> 0:18:19.880 depression create a natural wind tunnel that focuses and strengthens 0:18:19.920 --> 0:18:24.040 winds as they rake cross fast moving sand dunes. So 0:18:24.200 --> 0:18:26.800 sort of a funnel for wind here, the wind gauntlet. 0:18:26.840 --> 0:18:29.480 It hits this massive dry lake bed. And what does 0:18:29.520 --> 0:18:33.040 it pick up. Well, here's another fascinating thing to consider. 0:18:33.680 --> 0:18:37.040 The dust picked up from the depression here is made 0:18:37.119 --> 0:18:42.120 in large part of fossilized life. The sand in the 0:18:42.200 --> 0:18:47.320 former lake bed is made significantly of diatamite, also known 0:18:47.400 --> 0:18:51.639 as diatamaceous earth, which is a type of sedimentary rock 0:18:51.800 --> 0:18:55.080 usually soft in texture and light or white in color, 0:18:55.600 --> 0:19:00.000 and diatamite is formed over time from the fossilized body 0:19:00.440 --> 0:19:05.119 of diatoms, which are single celled organisms usually classified as 0:19:05.160 --> 0:19:07.439 the type of algae which live in the water and 0:19:07.520 --> 0:19:10.800 in the soil. They can sometimes gather together in colonies, 0:19:11.200 --> 0:19:16.240 and diatoms build protective cell walls or shells for themselves 0:19:16.600 --> 0:19:20.159 out of silica silicon dioxide, and after they die, the 0:19:20.200 --> 0:19:24.600 remains of these silica shells form a layer of sediment 0:19:24.920 --> 0:19:29.280 that can later become exposed and then become sand or dust. 0:19:29.720 --> 0:19:33.920 So the silicon dioxide shells of these tiny algae organisms 0:19:34.200 --> 0:19:37.480 living in the water so long ago become the dust 0:19:37.640 --> 0:19:40.600 that is blown across the ocean that helps nourish the 0:19:40.640 --> 0:19:44.879 Amazon rainforest, but also is used in everything from gardening 0:19:44.960 --> 0:19:48.639 to home construction to whatever I mean. Diatamacious earth is 0:19:49.040 --> 0:19:52.920 a commonly used material for all kinds of human industry, 0:19:53.320 --> 0:19:55.720 and it's just all the skeletons of these little dead 0:19:55.760 --> 0:19:56.440 life forms. 0:19:56.840 --> 0:19:57.560 Tiny process. 0:20:06.960 --> 0:20:10.400 But anyway back to dust storms. So dust storms often 0:20:10.440 --> 0:20:13.920 arise in these dry regions with less robust plant cover, 0:20:14.400 --> 0:20:17.880 especially after drought, when soil is vulnerable to wind erosion. 0:20:18.560 --> 0:20:20.960 When soil is very dry, it does not take a 0:20:21.000 --> 0:20:23.960 lot of force to lift dust particles into the air. 0:20:24.040 --> 0:20:27.159 According to the house Toff Works article, a wind of 0:20:27.200 --> 0:20:30.240 about nine miles per hour or fourteen point five kilometers 0:20:30.240 --> 0:20:33.240 per hour will kick up some dust. But of course, 0:20:33.280 --> 0:20:36.600 as winds become stronger, the uplift and transportation of dust 0:20:36.640 --> 0:20:40.600 and soil through the air becomes more violent. And one 0:20:40.680 --> 0:20:44.600 important process to understand here is something called saltation. The 0:20:44.720 --> 0:20:49.480 saltation as in related to Spanish word saltar, meaning like 0:20:49.520 --> 0:20:53.520 to jump. So when wind blows across loose, dry soil 0:20:53.680 --> 0:20:58.359 on the large scale, you will observe particles behaving differently 0:20:58.440 --> 0:21:02.600 based on their size. Very small dust particles can be 0:21:02.680 --> 0:21:05.320 picked up and become suspended in the air for long 0:21:05.359 --> 0:21:08.359 periods of time and can go very very high up. 0:21:08.400 --> 0:21:10.960 As we talked about in Part one, small particles of 0:21:11.040 --> 0:21:13.679 dust can float for hours or even days, and a 0:21:13.800 --> 0:21:16.719 dust storm can loft these small particles into a cloud, 0:21:16.760 --> 0:21:19.800 reaching hundreds of meters or thousands of feet into the air. 0:21:21.320 --> 0:21:24.879 Larger particles can be blown across the surface of the ground, 0:21:24.920 --> 0:21:28.240 sort of rolling in a process known as creeping, that's 0:21:28.280 --> 0:21:33.720 the term. But there are medium sized particles, these sort 0:21:33.720 --> 0:21:39.200 of sandy particles that engage in saltation, and saltation again 0:21:39.280 --> 0:21:42.800 means jumping. So these medium particles get blown along the 0:21:42.840 --> 0:21:46.400 surface of the ground until they are briefly carried aloft 0:21:46.480 --> 0:21:49.720 by lift. Maybe they hit an uneven surface and jump 0:21:49.840 --> 0:21:52.800 up as they're blown along, and then they bounce back 0:21:52.880 --> 0:21:56.359 down and hit the ground. And this causes a chain 0:21:56.440 --> 0:21:59.320 reaction because they come back down and they hit the ground, 0:21:59.600 --> 0:22:03.560 and that impact can cause other particles of soil or 0:22:03.600 --> 0:22:06.199 sand or whatever in the ground to bounce, to be 0:22:06.280 --> 0:22:10.320 knocked out of place, and they jump and then hit 0:22:10.400 --> 0:22:13.199 other particles and on and on, kind of like splashing 0:22:13.240 --> 0:22:17.280 in the water. So when a heavy wind hits dry soil, 0:22:17.359 --> 0:22:20.159 there will be a cloud of fine dust blown in 0:22:20.160 --> 0:22:24.439 the air by the air currents, but also a bombardment 0:22:24.520 --> 0:22:27.640 of leaping medium sized particles nearer to the ground. 0:22:28.680 --> 0:22:31.600 You know. This reminds me, of course, of a Frank 0:22:31.640 --> 0:22:36.160 Herbert's Dune, which I've been rereading. In the first part 0:22:36.200 --> 0:22:38.160 of the book, there's the scene where they take off 0:22:38.200 --> 0:22:43.119 in the ornithopter into the big sandstorm, and there's a 0:22:43.119 --> 0:22:45.400 discussion about, well, if you reach a certain altitude, it's 0:22:45.440 --> 0:22:48.480