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The Fat Electrician expounds yet again:
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To cite the title of her first book, Sabine Hossenfelder may be "Lost in Math."
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Today's encore selection -- from Why Sharks Matter by David Shiffman. Shark biodiversity and biogeography: "Recognizable sharks have been swimming in the ocean for more than 400 million years. This means that the first shark was on Earth not only well before dinosaurs trod the land but before trees existed. Though we've lost many species over the eons, sharks as a group have survived every mass extinction event in Earth's history -- which makes the conservation challenges they've faced in the past 50 years all the more heartbreaking. While we're talking about ancient sharks, let me assure you that, no, the giant and ancient megalodon is not still alive. It is definitely super-duper extinct. People claiming otherwise are lying to you, for reasons that remain unclear to me despite a decade of refuting this really strange folk legend. I've received death threats from people who believe I am part of a global conspiracy to hide the truth about megalodon. Once I even interacted with someone online who emphatically made the bizarre and obviously false claim that she had seen the US government rounding up and killing megalodons -- and that she had barely escaped with her life once the shark-killing soldiers spotted her. "Sharks' habitats are as diverse as the animals themselves. Some sharks are found on coral reefs, while others, like the Greenland shark, are found under Arctic ice. (Fun fact about Greenland sharks: they have been found with digested polar bear and reindeer meat in their stomachs. These are probably the remains of scavenging animals that drowned, but I enjoy imagining a polar bear getting slurped from below as it swims between ice floes.) Some sharks live in the open ocean, where they'll never see a hard surface their entire lives. Some sharks live in the deep sea, where it's so dark that sunlight never reaches. The megamouth shark, a deep-sea animal with the world's coolest scientific name -- Megachasma pelagios, which means 'the giant mouth of the deep' -- has bioluminescent gums that entice prey to swim right into its mouth. "US Navy Seals jokingly say that you can test whether there are sharks nearby by dipping your finger in the water and tasting it -- if it's salty, there are probably sharks around. While technically accurate -- there are sharks just about everywhere there's ocean -- the implication is incomplete, because there are also sharks that live in fresh water. No, I'm not just referring to the bull shark, which Discovery's Shark Week programming wrongly claims year after year is the only shark that can enter fresh water. I'm also talking about Glyphis sharks, sometimes known as river sharks, which live almost their entire lives in fresh water. Unfortunately, river sharks are some of the most critically endangered sharks in the world, in no small part because they live closer co humans than ocean-dwelling sharks do.
"What we already know about shark biodiversity is amazing, but it's what we don't know yet that many attendees at my public talks find shocking. We are still discovering new species all the time. A new species of chondrichthyan fish is discovered about every two weeks. Some of them get tons of media attention, like a new species of 'walking shark,' so called because they can crawl on their fins out of water for shore periods of time, or a new species of dogfish named after shark science legend Genie Clark (Genie's dogfish, Squalus clarkae). Others are little known outside of science nerd circles. There's plenty left to discover. (But no, that doesn't mean that megalodon is still hiding out there.) "Unfortunately, the threats these species face are as diverse as their habitats and color patterns, which means that there's no one-size-fits-all solution. For instance, creating no-fishing zones is less helpful to a species that moves around a lot and spends limited time in protected areas. Nor is a ban on selling shark fins especially useful for the many species killed for reasons having nothing to do with their fins. Generally speaking, any solution to a complex worldwide conservation problem simple enough to fit on a bumper sticker is perhaps too simple to be helpful."
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Today's selection -- from The Underworld by Susan Casey. The Tonga Trench:
“[If the island of] Tonga lacks in terrestrial heft, its surrounding waters are magisterial. To sail 180 miles south from the capital city of Nuku'alofa, on Tongatapu, is to find yourself floating atop thirty-five thousand feet of unquiet ocean above a seabed laceration known as the Horizon Deep. It's the deepest point in the 850-mile-long Tonga Trench, and the world's second-deepest spot, period—just a whisper shy of the Mariana Trench's Challenger Deep. You won't read about it in tourist brochures, but Tonga's ultradeep realm is one of the wonders of the underworld.
“In a contest of extremes, the Tonga Trench and the Mariana Trench are well matched. They're the inverted summits of Hades—a regal pair of forbidding destinations, as implacable as interstellar space. Like all hadal trenches they were created by subduction: as one tectonic plate dives beneath another, that collision bends the downgoing plate, forming a deep, V-shaped trench. There are approximately twenty-seven hadal trenches in the ocean, twenty-three of
which are located on the Ring of Fire, the belt of subduction zones around the Pacific margin. Only four of these trenches plunge below ten thousand meters (32,800 feet)—the Mariana, Tonga, Kermadec, and Philippine—and though they're well hidden from us, these titans are among the earth's most dramatic features.
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| The Tonga Trench constitutes the northern half of the Tonga-Kermadec subduction system, which extends 2,550 km (1,580 mi) between New Zealand and Tonga. |
“The Mariana Trench has starred in undersea horror movies, but the Tonga Trench is scarier, and that's before you factor in the eight pounds of plutonium in its depths, jettisoned during the aborted Apollo 13 mission. It's steeper, more severe, more seismically volatile-busier. At the Tonga Trench's north end, the Pacific plate is subducting beneath the Australian plate at the startling rate of nine inches per year. Nowhere else is a tectonic plate being gobbled with such relish, seamounts and volcanoes ingested like dinner rolls. It's a buffet of geological havoc.
“Every so often the Tonga Trench gets indigestion and belches out an earthquake from way down in the mantle: a majority of the world's deepest quakes originate there, rumbling hundreds of miles beneath the seabed. In 2009, a slab of the Pacific plate cracked as it was being subducted, and the Tonga Trench roared. A magnitude 8.1 earthquake triggered two magnitude 7.8 earthquakes, and all three earthquakes shook simultaneously, generating tsunami waves that ravaged Tonga and Samoa.
“As an encore, one of Tonga's seafloor volcanoes burped up a new island, more than two miles long and a half mile wide, now known as Hunga Tonga-Hunga Ha'apai. (In January 2022, this same volcano would be historical in its fury, unleashing an eruption that blasted steam and ash thirty-six miles up into the mesosphere, created a two-hundred-and-ninety-foot tsunami at its epicenter, and sent shock waves around the globe.) In 2019, another Tongan island called Lateiki disappeared into the depths during a submarine eruption, only to pop up again in a slightly different location."
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| author: Susan Casey | |||
| title: The Underworld: Journeys to the Depths of the Ocean | |||
| publisher: Doubleday | |||
| date: | |||
| page(s): 117-119 |
