1 00:00:01,920 --> 00:00:06,440 Speaker 1: Welcome to brain Stuff, a production of iHeart Radio, Hey 2 00:00:06,480 --> 00:00:10,920 Speaker 1: brain Stuff Lauren Vogelbaum here. Back in nineteen eleven, a 3 00:00:10,960 --> 00:00:15,840 Speaker 1: German meteorologist and geophysicist named Alfred Wegner was doing research 4 00:00:15,880 --> 00:00:18,919 Speaker 1: at a university library when he came upon a scientific 5 00:00:18,960 --> 00:00:23,240 Speaker 1: paper that listed ancient fossils of identical plants and animals 6 00:00:23,280 --> 00:00:26,360 Speaker 1: that have been found on both sides of the Atlantic Ocean. 7 00:00:27,440 --> 00:00:31,000 Speaker 1: This Scott Wagener to thinking about how the same organisms 8 00:00:31,000 --> 00:00:33,879 Speaker 1: could have evolved in two places that were separated by 9 00:00:33,880 --> 00:00:38,360 Speaker 1: thousands of miles of water. Some scientists believed that land 10 00:00:38,360 --> 00:00:42,640 Speaker 1: bridges had once existed between these places, but Vagener looked 11 00:00:42,640 --> 00:00:45,800 Speaker 1: at maps of the coastlines of Africa and South America 12 00:00:46,120 --> 00:00:49,200 Speaker 1: and came up with a different idea. What if those 13 00:00:49,240 --> 00:00:52,600 Speaker 1: continents had once been joined together and then moved apart 14 00:00:52,720 --> 00:00:55,120 Speaker 1: as part of a process that was still going on. 15 00:00:56,880 --> 00:01:00,240 Speaker 1: From that inspiration, Wagner came up with his theory of 16 00:01:00,280 --> 00:01:04,960 Speaker 1: continental drift, which at the time was widely derided as ridiculous. 17 00:01:05,800 --> 00:01:09,119 Speaker 1: By the nineteen fifties and sixties, however, scientists had come 18 00:01:09,160 --> 00:01:12,080 Speaker 1: around to thinking that Vagner might have been onto something, 19 00:01:12,480 --> 00:01:15,680 Speaker 1: and that pieces of the Earth's crust are slowly moving, 20 00:01:16,160 --> 00:01:18,880 Speaker 1: a process that not only explains many of the planet's 21 00:01:18,920 --> 00:01:23,920 Speaker 1: features but also helped make life on Earth possible. Plate 22 00:01:23,959 --> 00:01:26,839 Speaker 1: tectonics is the theory that the Earth's crust and upper 23 00:01:26,880 --> 00:01:31,119 Speaker 1: mantle are composed of numerous major and minor plates that 24 00:01:31,200 --> 00:01:35,839 Speaker 1: fit together tightly but are in continuous motion, moving sometimes 25 00:01:35,880 --> 00:01:40,040 Speaker 1: toward one another and other times apart. That movement is 26 00:01:40,080 --> 00:01:43,600 Speaker 1: known as plate motion or tectonic shift, and it's been 27 00:01:43,640 --> 00:01:46,959 Speaker 1: going on for a long long time. A study by 28 00:01:47,040 --> 00:01:50,560 Speaker 1: Johns Hopkins University researchers published in August of twenty nineteen 29 00:01:50,640 --> 00:01:54,320 Speaker 1: in the scientific journal Nature, concludes that plate tectonics began 30 00:01:54,440 --> 00:01:57,800 Speaker 1: about two point five billion years ago and has developed 31 00:01:57,840 --> 00:02:02,360 Speaker 1: gradually since then. For the article, this episode is based 32 00:02:02,400 --> 00:02:04,960 Speaker 1: on How Stuff Works. Spoken by email with Ray Russo, 33 00:02:05,280 --> 00:02:08,040 Speaker 1: an associate professor of geology at the University of Florida 34 00:02:08,280 --> 00:02:12,080 Speaker 1: and an expert in plate tectonics, He explained, the Earth 35 00:02:12,160 --> 00:02:15,560 Speaker 1: is a large scale heat engine. Heat left over from 36 00:02:15,560 --> 00:02:20,640 Speaker 1: planetary accretion, from gravitational compression, and from radioactive decay is 37 00:02:20,680 --> 00:02:25,079 Speaker 1: trapped in the Earth's interior. Because heat flows from warm 38 00:02:25,160 --> 00:02:28,680 Speaker 1: to cold regions, the Earth's interior heat tends to flow 39 00:02:28,840 --> 00:02:32,400 Speaker 1: toward its cold surface. The most efficient way for this 40 00:02:32,480 --> 00:02:35,160 Speaker 1: heat to get from the deep interior to the Earth's 41 00:02:35,160 --> 00:02:39,959 Speaker 1: surface is by convection. So on a large scale, hot 42 00:02:40,000 --> 00:02:44,240 Speaker 1: mantle material rises and replaces cold mantle material that has 43 00:02:44,280 --> 00:02:49,400 Speaker 1: developed at Earth's surface. He continued. The cold material is 44 00:02:49,560 --> 00:02:54,120 Speaker 1: essentially the Earth's rigid plates. These plates become dense as 45 00:02:54,160 --> 00:02:57,519 Speaker 1: they cool, and eventually they become dense enough to sink 46 00:02:57,680 --> 00:03:01,440 Speaker 1: into the mantle, cooling the planet, disturbing the mantle on 47 00:03:01,480 --> 00:03:06,520 Speaker 1: a global scale. In a nutshell, that's plate technonics. The 48 00:03:06,560 --> 00:03:10,760 Speaker 1: plates move really, really slowly. The average speed is just 49 00:03:10,960 --> 00:03:14,280 Speaker 1: zero point six inches or one point five centimeters per year, 50 00:03:14,760 --> 00:03:17,880 Speaker 1: though scientists have differing opinions on whether the movement is 51 00:03:17,919 --> 00:03:22,480 Speaker 1: slowing down or increasing. The plates interact along their boundaries 52 00:03:22,520 --> 00:03:25,720 Speaker 1: in three different ways. Where two plates move away from 53 00:03:25,760 --> 00:03:29,320 Speaker 1: each other, it creates a divergent boundary, a zone where 54 00:03:29,320 --> 00:03:33,360 Speaker 1: earthquakes are common and hot magma or molten rock rises 55 00:03:33,440 --> 00:03:37,960 Speaker 1: from the mantle to the surface to form new crust. Conversely, 56 00:03:38,120 --> 00:03:42,160 Speaker 1: in places where two plates come together, a convergent boundary occurs. 57 00:03:42,720 --> 00:03:45,280 Speaker 1: The impact of the plates in those places can cause 58 00:03:45,320 --> 00:03:47,880 Speaker 1: the edges to buckle and push up to form a 59 00:03:47,920 --> 00:03:51,200 Speaker 1: mountain range, or else bend to create a deep trench 60 00:03:51,280 --> 00:03:55,520 Speaker 1: in the ocean floor. Chains of volcanoes often form parallel 61 00:03:55,520 --> 00:03:59,800 Speaker 1: to the boundaries. Convergent boundaries create continental crust but destroy 62 00:04:00,040 --> 00:04:03,880 Speaker 1: rust that's part of the ocean floor. Meanwhile, in a 63 00:04:03,960 --> 00:04:08,240 Speaker 1: transform plate boundary, two plates will slide past one another. 64 00:04:08,840 --> 00:04:12,640 Speaker 1: Crust along a transform plate boundary will be cracked and broken, 65 00:04:13,000 --> 00:04:15,880 Speaker 1: but unlike the other two types of boundaries, it won't 66 00:04:15,960 --> 00:04:20,160 Speaker 1: create any new crust. Earthquakes are common along these faults. 67 00:04:21,760 --> 00:04:25,919 Speaker 1: As Russo explained, plate tectonics profoundly affect our entire planet 68 00:04:26,040 --> 00:04:29,640 Speaker 1: and all of its natural processes. One big reason is 69 00:04:29,680 --> 00:04:31,919 Speaker 1: that some of the movement of the plates causes the 70 00:04:32,000 --> 00:04:35,599 Speaker 1: formation of volcanoes, but basically breaks in the crust that 71 00:04:35,760 --> 00:04:39,520 Speaker 1: serve as vents for heat and lava, and their eruptions 72 00:04:39,640 --> 00:04:44,000 Speaker 1: continually resurface the ocean basins that account for seventy of 73 00:04:44,040 --> 00:04:49,359 Speaker 1: the Earth's surface. Just as importantly, volcanic activity associated with 74 00:04:49,400 --> 00:04:53,720 Speaker 1: tectonic plate movement causes lighter, less dense minerals to separate 75 00:04:53,960 --> 00:04:56,880 Speaker 1: from the heavier, denser ones in the Earth's mantle, which 76 00:04:56,920 --> 00:05:00,240 Speaker 1: results in the development of continents. You know where most 77 00:05:00,279 --> 00:05:03,880 Speaker 1: of us live, and the fertile soil that allows plants 78 00:05:03,880 --> 00:05:07,280 Speaker 1: to grow and produce both food and oxygen that sustains 79 00:05:07,400 --> 00:05:12,080 Speaker 1: humans and large animal life. Tectonic plate movement also helped 80 00:05:12,080 --> 00:05:15,000 Speaker 1: in numerous ways to create the conditions that make life 81 00:05:15,000 --> 00:05:18,880 Speaker 1: on Earth possible. It leads, for example, to the interaction 82 00:05:19,000 --> 00:05:22,040 Speaker 1: of hot volcanic rocks with water in the ocean, and 83 00:05:22,279 --> 00:05:25,200 Speaker 1: the leaching of ions from those rocks is what controls 84 00:05:25,240 --> 00:05:30,560 Speaker 1: the ocean's salinity. Russo explained. Life evolved in the oceans 85 00:05:30,600 --> 00:05:33,800 Speaker 1: in the presence of this ion rich water, and humans, 86 00:05:33,839 --> 00:05:37,680 Speaker 1: for example, have blood salinity equivalent to the salinity of seawater. 87 00:05:37,880 --> 00:05:42,719 Speaker 1: As a direct consequence, by rearranging the configuration of the 88 00:05:42,760 --> 00:05:46,960 Speaker 1: continents and the ocean basins, plate tectonics also influences the 89 00:05:47,000 --> 00:05:51,280 Speaker 1: planet's climate, Russo said. For example, the current shapes of 90 00:05:51,279 --> 00:05:56,200 Speaker 1: the ocean basins continually supply warm equatorial waters to polar regions, 91 00:05:56,680 --> 00:05:59,920 Speaker 1: keeping the planet from developing very great extremes of surface 92 00:06:00,000 --> 00:06:05,480 Speaker 1: temperature between equator and poles. The mountains formed by tectonics 93 00:06:05,520 --> 00:06:09,479 Speaker 1: are also among the planet's most important carbon dioxide sinks, 94 00:06:09,480 --> 00:06:12,960 Speaker 1: helping to draw down atmospheric CEO two levels by forming 95 00:06:13,040 --> 00:06:17,800 Speaker 1: new minerals. That process increases and decreases in response to 96 00:06:17,920 --> 00:06:22,360 Speaker 1: shifts in temperature, enabling the mountains to act as giant thermostats. 97 00:06:23,960 --> 00:06:27,400 Speaker 1: The gradual shifting of the continental masses has also played 98 00:06:27,400 --> 00:06:32,560 Speaker 1: an important role in biological evolution. Russo said, Speciation the 99 00:06:32,640 --> 00:06:35,920 Speaker 1: development of new species, occurs when a single group of 100 00:06:35,960 --> 00:06:38,760 Speaker 1: plants or animals is divided into two groups that are 101 00:06:38,839 --> 00:06:43,120 Speaker 1: no longer in reproductive contact, as for example, often happens 102 00:06:43,160 --> 00:06:46,400 Speaker 1: when a supercontinent breaks up and new ocean basins form 103 00:06:46,560 --> 00:06:51,680 Speaker 1: between its continental fragments. All of this may help explain 104 00:06:51,760 --> 00:06:55,080 Speaker 1: why life is so prevalent on Earth but apparently absent 105 00:06:55,200 --> 00:06:58,440 Speaker 1: on other planets in our Solar System. While Mars and 106 00:06:58,640 --> 00:07:02,240 Speaker 1: Venus have hot interior years and their surfaces show signs 107 00:07:02,279 --> 00:07:05,560 Speaker 1: of recent deformation, Earth is the only planet in the 108 00:07:05,600 --> 00:07:09,960 Speaker 1: Solar System whose surface is divided into plates. Mercury, the 109 00:07:10,040 --> 00:07:19,600 Speaker 1: fourth rocky planet, is no longer geologically active. Today's episode 110 00:07:19,640 --> 00:07:22,120 Speaker 1: is based on the article plate tittonics puts together the 111 00:07:22,160 --> 00:07:25,320 Speaker 1: puzzle of Earth's shifting crust on how stuff Works dot com, 112 00:07:25,320 --> 00:07:28,240 Speaker 1: written by Patrick J. Keaiger. Brain Stuff is production of 113 00:07:28,240 --> 00:07:30,360 Speaker 1: by Heart Radio in partnership with how stuff works dot 114 00:07:30,400 --> 00:07:33,560 Speaker 1: Com and is produced by Tyler Klang. For more podcasts 115 00:07:33,680 --> 00:07:36,720 Speaker 1: my Heart Radio, visit the iHeart Radio app, Apple Podcasts, 116 00:07:36,760 --> 00:07:38,560 Speaker 1: or wherever you listen to your favorite shows.