History Of The Earth



We've concentrated the history of Planet Earth into one year. Follow the geology podcasts chronologically from the origin of the Earth to the origin of Mankind.


  • Episode 397 Carbonatites


    Carbonatites are strange igneous rocks made up mostly of carbonates – common minerals like calcite, calcium carbonate. Igneous rocks that solidify from molten magma usually are high-temperature rocks containing lots of silicon which results in lots of quartz, feldspars, micas, and ferro-magnesian minerals in rocks like granite and basalt. Carbonatites crystallize from essentially molten calcite, and that’s really unusual. Most carbonatites are intrusive, meaning they solidified within the earth, and it wasn’t until 1960 that the first carbonatite volcano erupted in historic times, proving that they form from cooling magma. The eruption at Ol Doinyo Lengai in Tanzania occurred on a branch of the East African Rift System, and most carbonatites are associated with these breaks in continental crust where eventually a new ocean may form. Mt Lengai, Tanzania, photo by Clem23 (Creative Commons License - source)Eruptions at Lengai, whose name means “mountain of god” in the Maasai language, are the lowest-temperature

  • Episode 396 Turbidity currents


    As near as I can tell in the original daily series in 2014, I never addressed the topic of turbidity currents and their sedimentary product, turbidites. But they account for the distribution of vast quantities of sediment on continental shelves and slopes and elsewhere. You know what turbid water is: water with a lot of suspended sediment, usually fine mud particles. In natural submarine environments, unconsolidated sediment contains a lot of water, and when a slurry-like package of sediment liquifies, it can flow down slopes under gravity, sometimes for hundreds of kilometers.It isn’t correct to think of these streams of water and sediment as like rivers on the sea floor. Rivers transport sediment, whether boulders or sand or silt or mud, through the traction, the friction of the moving water. Turbidity flows are density flows, moving because the density of the water-sediment package is greater than the surrounding water. That means they can carry larger particles than usual. Turbidite formation. Image

  • Episode 395 Connections


    This episode is about some of the interesting connections that arise in science.We’ll start with me and my first professional job as a mineralogist analyzing kidney stones. My mineralogy professor at Indiana University, Carl Beck, died unexpectedly, and his wife asked me as his only grad student to carry on his business performing analysis of kidney stones. Beck had pioneered the idea of crystallographic examination to determine mineralogy of these compounds because traditional chemical analysis was misleading. For example, some common kidney stones are chemically calcium phosphates and calcium carbonates – but they are hardly ever calcium carbonate minerals. That makes a big difference in terms of treatment, because calcium carbonate minerals can be dissolved with acids, while calcium phosphate cannot. The carbonate is actually part of the phosphate mineral structure, partially substituting for some of the phosphate. Other subtleties of mineral crystallography can distinguish between different minerals and

  • Episode 394 The Mangrullo Formation of Uruguay


    Today we’re going back about 280 million years, to what is now Uruguay in South America. 280 million years ago puts us in the early part of the Permian Period. Gondwana, the huge southern continent, was in the process of colliding with North America and Eurasia to form the supercontinent of Pangaea. South America, Africa, Antarctica, India, and Australia had all been attached to each other in Gondwana for several hundred million years, and the extensive glaciers that occupied parts of all those continents were probably still present in at least in highlands in southern South America and South Africa, as well as Antarctica. But the area that is now in Uruguay was probably in cool, temperate latitudes, something like New Zealand or Seattle today. The connection between southern South America and South Africa was a lowland, partially covered by a shallow arm of the sea or perhaps a broad, brackish lagoon at the estuary of a major river system that was likely fed in part by glacial meltwater from adjacent mounta

  • Episode 393 The Mountains of the Moon


    Today we’re going to the Mountains of the Moon – but not those on the moon itself. We’re going to central Africa. There isn’t really a mountain range specifically named the Mountains of the Moon. The ancients, from Egyptians to Greeks, imagined or heard rumor of a mountain range in east-central Africa that was the source of the river Nile. In the 18th and 19th centuries, explorations of the upper Nile found the sources of the Blue Nile, White Nile, and Victoria Nile and identified the Mountains of the Moon with peaks in Ethiopia as well as 1500 kilometers away in what is now Uganda. Today, the range most closely identified with the Mountains of the Moon is the Rwenzori Mountains at the common corner of Uganda, the Democratic Republic of Congo, and Rwanda. This location is within the western branch of the East African Rift system, an 8,000-kilometer-long break in the earth’s crust that’s in the slow process of tearing a long strip of eastern Africa away from the main continent. We talked about it in the episo

  • Episode 392 Ophiolites


    Today’s episode focuses on one of those wonderful jargon words geologists love to use: Ophiolites.It’s not a contrived term like cactolith nor some really obscure mineral like pararammelsbergite. Ophiolites are actually really important to our understanding of the concept of plate tectonics and how the earth works dynamically. The word goes back to 1813 in the Alps, where Alexandre Brongniart coined the word for some scaly, greenish rocks. Ophiolite is a combination of the Greek words for snake and stone, and Brongniart was also a specialist in reptiles. So he named these rocks for their resemblance to snake skins. Fast forward about 150 years, to the 1960s. Geophysical data, deep-sea sampling, and other work was leading to the understanding that the earth’s crust is fundamentally different beneath the continents and beneath the oceans—and we found that the rocks in the oceanic crust are remarkably similar to the greenish, iron- and magnesium-rich rocks that had been labeled ophiolites long ago and largely i

  • Episode 391 Valles Marineris


    In today's episode we’re going to space. Specifically, Mars. You didn’t really think that earth science is really limited to the earth, did you? Our topic today will be the Valles Marineris.The Valles Marineris is a long series of canyons east of Olympus Mons, the largest mountain in the solar system. These canyons are about 4,000 km long, 200 km wide and up to 7 km (23,000 ft) deep. On terrestrial scales, the Valles Marineris is as long as the distance from New York to Los Angeles. That’s about the same as Beijing to Hong Kong or Madrid to Copenhagen for our international listeners. They are as wide as central Florida, central Italy, or the middle of the Korean peninsula. Two and a half times deeper than Death Valley, though only about 60 percent of the depth of the Marianas Trench, the lowest point on earth.Valles Marineris Image Courtesy NASA/JPL-CaltechNot to be outdone, our planet, Earth, has even bigger valleys. These occur at the oceanic ridges, where plate spreading takes place. The longest rift

  • Episode 390 Mud Volcanoes


    As the name implies, mud volcanoes are eruptions of mud – not molten rock as in igneous volcanoes.  They’re found all around the world, amounting to about a thousand in total number known. The one thing they have in common is hot or at least warm water, so they occur in geothermal areas especially, but they also are found in the Arctic.They range in size from tiny, just a few meters across and high, to big things that can cover several square miles. In Azerbaijan some mud volcanoes reach 200 meters, 650 feet, in height, and around the world many of them do have conical, volcano-like shapes. But there are others that are just low mounds, more like a shield volcano. A little (15-cm) mud volcano in New Zealand. Photo by Richard Gibson.The mud is often enough just a slurry of suspended fine-grained sediment that mixes with the hot water. And by hot water, we don’t necessarily mean incredibly hot – mud volcano temperatures as cold as a couple degrees Centigrade are known, but most are associated with tempera

  • Cretaceous and Cenozoic Vertebrates compilation


    Smilodon and dire wolves (drawing by Robert Horsfall, 1913)Running time, 1 hour. File size, 69 megabytes. This is an assembly of the episodes in the original series from 2014 that are about Cretaceous and Cenozoic vertebrates. I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.Thanks for your interest and support!

  • Triassic and Jurassic Vertebrates compilation


    Morganucodon, a possible early mammal from the Late Triassic. Length about four inches.Drawing by FunkMonk (Michael B. H.) used under Creative Commons license. Running time, 1 hour. File size, 68 megabytes.This is an assembly of the episodes in the original series from 2014 that are about Triassic and Jurassic vertebrates. As usual, I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.Thanks for your interest and support!

  • Episode 389 Vanadium


    Vanadium is a metal, and by far its greatest use is in steel alloys, where tiny amounts of vanadium improve steel’s hardness, toughness, and wear resistance, especially at extreme temperatures. As I reported in my book What Things Are Made Of, more than 650 tons of vanadium was alloyed with iron to make the steel in the Alaska Pipeline, and there’s no good substitute for vanadium in strong titanium alloys used in jet planes and other aerospace applications. Vanadium isn’t exactly one of the well-known elements, but in terms of abundance in the earth’s crust, most estimates indicate that there’s more vanadium than copper, lead, or tin. But it’s difficult to isolate, and it wasn’t produced chemically as a chloride until 1830, when Swedish chemist Nils Sefström named it for the Norse goddess of beauty, Vanadis, perhaps better known as Freyja. It wasn’t until 1867 that pure vanadium metal was isolated by British chemist Henry Roscoe, whose work on vanadium won him the name of the vanadium mica roscoelite.As a mi

  • Episode 388 Folds in Algeria


    You may have seen some of the spectacular images of the earth in southern Algeria, curves and colors like some Picasso in the opposite of his cubist period. If you haven’t, check out the one from NASA, below. The ovals and swirls, with their concentric bands, are immediately obvious to a geologist as patterns of folds, but not just linear folds like many anticlines and synclines form. These closed ovals represent domes and basins – imagine a large scale warping, both up and down, in a thick succession of diverse sedimentary rocks, like sets of nested bowls, some of them right-side up and some inverted, then all sliced off halfway through. But “obvious to a geologist” has plenty of limitations in a space image. Without knowing more information, it’s difficult to be sure if an oval is a basin or a dome. And you can speculate, but without some ground truth, it’s challenging to be sure what the rock types are. Ahnet-Mouydir, Hoggar Mountains, Algeria. NASA image - sourceThis area, called the Ahnet-Mouydir,

  • Episode 387 Geology of Beer


    It isn’t true that all geologists drink beer. But many do, and I’m one of them. Today I’m going to talk about the intimate connection between geology and beer. Beer is mostly water, and water chemistry has everything to do with beer styles. And water chemistry itself depends mostly on the kinds of rocks through which the water flows. You know about hard and soft water – hard water has more dissolved chemicals like calcium and magnesium in it, and while salts of those chemicals can precipitate out of hard water, making a scum on your dishes, they also can be beneficial to development of bones and teeth. In the United States, the Midwest and Great Plains have some of the hardest water because of the abundant limestones there, and in Great Britain, southern and eastern England have harder water than Scotland for similar reasons. But it wasn’t limestone that made Burton-upon-Trent a center of brewing in the 19th Century, when it was home to more than 30 breweries. The water there is rich in sulfate which comes f

  • Paleozoic Vertebrates compilation


    Ganoid fish from an old textbook (public domain)Running time, 1 hour. File size, 70 megabytes.This is an assembly of the 15 episodes in the original series from 2014 that are about Paleozoic vertebrates. I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.Thanks for your interest and support!