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Uploaded:2014-12-20
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SciShow News takes you to the depths of the Earth, where the world’s most abundant mineral is found, and to the Arabian Sea, where a strange population of whales has been living in isolation for 70,000 years!

Hosted by: Hank Green
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Sources:
http://www.eurekalert.org/pub_releases/2014-12/p-ash120114.php
http://www.eurekalert.org/pub_releases/2014-12/wcs-ash120314.php
http://www.eurekalert.org/multimedia/pub/83531.php?from=283787 [image of Arabian Whale]
http://www.tulane.edu/~sanelson/eens1110/earthint.htm
http://blogs.agu.org/geospace/2014/06/06/earths-abundant-mineral-finally-gets-name/
http://www.eurekalert.org/pub_releases/2014-12/dnl-ema121214.php

 The world's most abundant mineral


     You'd think that the most abundant mineral on Earth would have a name, right? I mean, we named one of the rarest minerals on Earth; we actually called it "fornacite."

     Not actually a huge fan of that one.

     Vesuvianite or kosmochlor, those are mineral names you can get behind! But the mineral that makes up 38% of the entire earth was unnamed until last week, when researchers in a study published in the journal Science named it "bridgmanite."

     Now, we've known about bridgmanite, a high-density form of magnesium iron silicate, for decades. The problem is, it almost always entirely exists within the Earth's lower mantle, a layer of hot, dense rock between 670 and 2,900 kilometers below the surface.

     Researchers were only able to study it indirectly, by studying variations in seismic waves as they traveled through the planet's interior. The density and composition of different minerals can alter the direction and speed of those waves.

     So geologists theorized that it was there, but in order to name a mineral you need a physical sample to test and to prove to people that it exists. That's one of the totally understandable rules that's been established by the international mineralogical association, a group that standardizes and approves mineral names.

     So, instead of digging down 670 kilometers to grab some bridgmanite (which is impossible) scientists studied a meteorite that fell to Earth over 130 years ago. Both asteroids and Earth share similar elements, like magnesium and iron.

     And when these elements endure intense heat and pressure, we're talking 2100°C and pressure that's 240,000 times greater than at sea level, bridgmanite can form. These conditions can occur both beneath the Earth's surface and in the collisions of asteroids in space.

     As it happened, the debris of one such stellar collision struck Australia in 1879, a meteorite named "The Tenham," which was formed 4.5 billion years ago.

     Using tightly controlled x-ray beams, geologists were able to find veins of bridgmanite in the rock and create a highly detailed structural map of its grains.

     They gathered enough data on the mineral's properties to prove its existence to the international mineralogical association.

     The scientists named it after Percy Bridgman, an American scientist who won the Nobel Prize in 1946 for his work on the physics of high pressure.

     So here's my open letter to bridgmanite: I'm sorry that it took us four and a half billion years to figure out your name.

 Oddball humpback whales (2:27)


     Another thing that's been overlooked for way too long; a unique and apparently totally isolated population of humpback whales living in the Arabian Sea.

     Humpbacks hold the record for conducting the longest migration of any mammal. Twice a year, most of these giants travel up to 9,000 kilometers between their feeding grounds near the pole and their breeding grounds in the tropics.

     And I say most because the population of about 100 humpbacks recently identified in the Arabian Sea just doesn't migrate. A new study suggests that these non-migratory whales have remained isolated from the other humpbacks for 70,000 years, making them the most genetically distinct humpback population on Earth.

     A population is basically a group of animals that breed together over a long period. This causes their genes to mutate in a similar fashion and at a certain rate from generation to generation, and that is known as the population's mutation rate.

     But using the DNA from the Arabian whales and humpbacks from around the world, biologists found that Arabian humpbacks have a totally different mutation rate. The math suggested that they had split from a population in the southern Indian Ocean 70,000 years ago before heading into the Arabian Sea.

     This would have been during the last ice age, when cold temperatures increased the local nutrient supply, turning that sea into a feeding ground. And apparently the whales just kept to themselves!

     Researchers point out that despite their isolation, the Arabian whales aren't a new species or a new subspecies. Instead, they're just fascinating and weird.

     Just like bridgmanite! And also just like most of the stuff we talk about here on SciShow News.

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