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EarthDate

Switch Energy Alliance

EarthDate is a short-format weekly audio program delivering concise, science-based stories about the Earth: its geology, environments, and the processes that shape our planet over deep time and today. Beginning in 2026, EarthDate is managed by Switch Energy Alliance and hosted by SEA's founder Dr. Scott W. Tinker. Together, we explore earth systems, natural resources, and their relevance to everyday life, with a focus on clear, accessible science education for broad audiences. EarthDate is written and directed by Emmy-winning filmmaker Harry Lynch, and researched by Lynn Kistler. We search for captivating stories to remind listeners that science can enlighten, educate and entertain.

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Tuesday · 2 min
Gold is Abundant
Gold is rare. Except in one place on Earth that it’s incredibly plentiful. But we’ll probably never get to it. Over the course of human civilization, people have searched for gold. Still, we haven’t found much – 220,000 tons across all those centuries. By comparison, we’ve mined seven times as much silver. And 3,000 times more copper. But we now know there’s much, much more gold on Earth. When the planet formed, more than 4 billion years ago, many metals swirled together in Earth’s molten magma, gold among them. Being heavy, it was pulled toward the center, into Earth’s core, by the force of gravity. There it bonded with abundant iron. And there it has mostly stayed. But Earth’s interior is not static. The molten magma sometimes upwells toward the surface. Over millions of years these magma currents have carried small amounts of gold and other metals out of the core. Earthquakes and shifting tectonic plates then brought that magma toward the surface. Some of it precipitated out in veins, which we have mined. And some of that eroded into rivers and streams, and we gathered it there too. Because it’s valued, and doesn’t oxidize, most of the gold we’ve found over the years still exists in pure form and gold-rich alloys, and is still in use – in jewelry, art, electronics, even medicine. It may be precious, but it’s not scarce. It’s just that Earth has limited our access.
September 8 · 2 min
Life on Mars?
Is there life on Mars? That’s the question NASA wanted its first Mars mission to answer – in 1976. They designed their remarkable Viking rover -- well before modern computers -- to collect and test soil samples, 140 million miles from Earth. First, Viking added a nutrient solution to the soil, looking for carbon dioxide that microbes would produce if they consumed it. And the test showed a small amount! Next, Viking incubated the sample to see if microbes, if present, could produce organic matter. A tiny amount was detected! But the third test would be conclusive. The rover incinerated the soil to gasify its compounds, then used a spectrometer to evaluate them. If there were organic matter, it would surely show up. But it didn’t. At the time, the answer was: no life on Mars. Several decades later, subsequent missions, using different tests, did find signs of microbial activity. So NASA went back to review the Viking data. With 50 years of new understanding, many scientists now believe that salt compounds in the Martian soil, when heated, would have destroyed any organic matter. Meaning Viking’s gas test may not have been designed or understood correctly. Today, there’s still no solid proof that Mars has microbial life. But new -- and half-century old -- tests haven’t ruled it out either!
September 1 · 2 min
Warm Springs for Winter Manatees
A large manatee can top 1000 pounds and eat 15% of its weight in seagrass each day. That may sound hardy, but manatees are actually very sensitive. There are three species, all adapted only to the constant warm waters of the tropics. But the West Indian manatee has found a way to survive Florida winters by taking advantage of the state’s geology. As temperatures drop, manatees leave coastal waters and swim up rivers toward headwater springs. Florida has hundreds of springs, more than any other state, and some are huge, pumping out millions of gallons a day. The springs are fed by rainwater that percolates through Florida’s limestone bedrock, flows underground, is heated by geothermal energy, then emerges to form warm, clear pools that feed rivers. The spring pools are home to large ecosystems of many species -- including, in winter, manatees, who come by the hundreds to spend the cold months lounging, and eating. Like so many things in nature, the springs are under pressure from human development. Florida cities and agriculture pull water from the aquifer, reducing flow into the pools. Fertilizer seeps into the groundwater and enters the springs, clogging them with algae. Despite that, the manatees’ numbers are increasing, due to conservation efforts by Florida preservation groups. A success story of shared resource use that can hopefully sustain these remarkable creatures long into the future.
August 25 · 2 min
Mapping a Killer
In the mid-1800s, London’s SoHo neighborhood was a terrible smelling place to live, as raw sewage ran through the gutters into open cesspools. When a cholera epidemic broke out, 600 people died and many remaining residents fled, fearing – as was common then – that foul air spread the disease. Local physician John Snow didn’t buy it. Ten years earlier, he had proposed that cholera spread through contaminated water. But lacking proof, he was ignored. With an outbreak on his doorstep, he saw an opportunity to test his hypothesis – and save his neighborhood. First, he obtained the addresses of every person who had died. Then he walked the streets plotting the deaths, and everything else, on a map. Soon a pattern emerged. Most of the cases clustered around one public water well. He began interviewing area residents. Locals with their own private wells had not gotten sick. Workers at a nearby pub, who drank a daily ration of beer instead of pump water, were also spared. Snow convinced local authorities that water from the well was to blame, and persuaded them to remove the pump handle, forcing residents to draw their water elsewhere. Immediately the cholera outbreak ended. With his cholera map, Snow had begun the field of evidence-based epidemiology. This was well before germ theory and microscopes could identify the true culprit, the cholera bacteria, that had spread through sewage leaking into the water supply.
August 18 · 2 min
Ocean Cleanup
Plastic has remarkable value to humans. But it’s also a major source of ocean plastic pollution. Most of it is nets and rope from fishing boats, or municipal garbage that’s carried down rivers into the ocean. There it accumulates in spinning gyres of plastic, twice the size of Texas. Large pieces eventually break down into fragments and microplastics. But because plastic is made to be durable, it won’t degrade any farther than that. Wouldn’t it be great if we could clean it up? That’s what a Dutch teenager thought when he was diving in Greece and saw more plastic bags than fish. He created a high school science project -- that has since grown into an international nonprofit, called The Ocean Cleanup, employing engineers, marine biologists and collection teams. They set up huge U-shaped nets that float with the current in the spinning gyres, in the top few feet of water where most plastics (but few fish) are. These gradually capture the debris, which their boats collect and haul to shore. They’ve also installed collection systems at the mouths of rivers to intercept plastic before it enters the ocean. Together, their systems have captured millions of pounds of plastic waste, which they sort, recycle or properly landfill. There’s much more to do, but they’ve inspired governments and other nonprofits to work on plastic waste management on land and at sea. Hopefully, with growing awareness, we can all make a meaningful difference in ocean plastic pollution.
August 11 · 2 min
The Right Kind of Sand
Sand is incredibly common. There are oceans of it – in oceans, and deserts too. But, for our purposes, that’s not the right kind of sand. We use sand in concrete, to make bridges and roads, buildings, houses and power plants. We use it in glassmaking, for windows, computer chips, solar panels and much more. We use it for hydraulic fracturing, to prop open cracks in shale deposits so oil and gas can flow. In all, we use billions of tons of sand every year. But only a certain kind will do. Beach sand is often mixed with salt. If used in concrete, it can corrode the reinforcing steel. And the grains of beach sand, and especially desert sand, are often rounded by waves or wind. Concrete needs angular grains that lock together. Hydraulic fracturing needs hard grains that can withstand pressure. And glassmaking needs almost pure quartz. That means, for most uses, the ideal sand is angular, well-sorted quartz. And that’s only found in a few places. Rivers and streams are natural sorting machines. They break down and wash out weaker minerals, leaving quartz sand in bars and banks, which can be dredged or mined. Through time, many of these quartz sand deposits were lithified into sandstone, which today can be ground back into sand. Our demand is so great that this once common material is becoming scarce, spawning a lucrative international trade -- for the right kind of sand.
August 4 · 2 min
Dangerous Downbursts
In 1985, a passenger jet landing at DFW airport was forced to the ground by an unusual downward blast of wind called a downburst. The plane struck cars on the highway and a water tank, then crashed on the airfield, killing more than 100 people. It was the third such fatal crash in a decade. So, the FAA set out to invent a new warning system for these dangerous wind events. A downburst is a sinking column of air within a thunder cloud that accelerates toward Earth, reaching speeds over 100 miles an hour. When it strikes the ground, it blasts out in all directions, like a mammoth version of water splashing in a sink. These winds are strongest just 10 to 30 feet from the ground and travel horizontally outward in all directions. They can fell trees like a tornado’s whirling winds, but they all fall in the same direction, like dominoes. For aviation, the first step was training pilots to look for visual signs – expanding rings of dust on the ground below, or sharply defined shafts of intense rain. Technologically things were more complex. Vulnerable airports installed a network of wind sensors, as well as advanced Doppler radar that could track wind speeds. All fed into an early alert system. By 1994, 46 high traffic airports had installed these systems. They haven’t had a single downburst accident since -- and technology continues to improve. A triumph of aviation safety.
August 4 · 2 min
Beating the Heat
Before modern energy gave us modern air conditioning, we had sweat to keep us cool. And shade. And maybe a jump in a lake. Animals still rely on those today to beat the heat. Horses, like humans, sweat. When the sweat evaporates, it cools the skin. Dogs, antelopes and some birds pant, drawing breath rapidly across their tongues and throats, where evaporative cooling brings down the temperature of blood near the skin surface. Other birds vibrate the flaps of skin on their throats to circulate air around blood vessels found there. Elephants do something similar, cooling blood vessels in their huge ears, by flapping them. Camels and toucans draw air across blood vessels in their noses. Rodents and amphibians burrow in the soil or under leaf litter, where it’s cooler and moister. Some toads burrow and go dormant until the next rain comes. Some even form a protective cocoon of their own shed skin. Deer, doves and many other creatures seek shade during the heat of the day, resting silently to keep metabolic rates low. Even fish seek shade underwater, under overhanging rocks or docks. Or they retreat to the dark depths, where the water’s cooler. Speaking of water, buffalo and birds splash in shallow pools. Vultures, maybe not surprisingly, go so far as to pee on their own legs to cool themselves off. Which just goes to show, when the heat rises, animals have found amazing ways to adapt.
August 4 · 2 min
Mangrove Mayhem
If you’ve been on a boat, pretty much anywhere in the tropics, you’ve seen mangrove forests. There are at least 75 species of these small trees, evolved to live in harsh tidal conditions, their roots in sand, their trunks often submerged in saltwater. There, they can form dense thickets that protect the coast from ravaging waves and storm surges. And that’s just one of their benefits. Mangroves’ arching root networks trap and stabilize sediment to help build up the coast. In the process, they filter and clean coastal water. Those same roots serve as nurseries, sheltering the young of many fish and crustacean species. While the forests provide timber for local human populations, and store carbon. But mangroves are in peril -- from coastal development, agriculture, and especially aquaculture. Shrimp farmers in Asia are responsible for a third of global mangrove destruction, as they clear forests to build their ponds. Early efforts to replant the forests had failed. Until an innovative Florida ecologist realized that mangroves thrive best when their roots are wet only 30% of the time and dry the rest, as the tide comes and goes. He used a backhoe to regrade the coastline to encourage those conditions. Within three years, the resilient mangroves had returned. His methods proved so successful, they’ve been adopted globally, in a preservation program that intends to bring 20% of mangrove coverage back within the decade.
August 4 · 2 min
Turning Up the Urban Heat
On another episode, we told you about urban heat islands. Buildings and asphalt absorb summer heat -- from sun and air, cars and trucks, power plants and air conditioning -- and hold it, driving city temperatures far higher than surrounding areas, sometimes to devastating effect. Urban heat islands have killed thousands. But new studies of over 3,000 cities around the world show they’ve saved many more! That’s because heat islands also hold heat in winter, as buildings, transportation and industry ‘leak’ heat into the environment. The result, just as in summer, is that cities can be 10 degrees Fahrenheit warmer. That means less energy required for heating homes and buildings. And, it means many fewer deaths from hypothermia, heart attacks and respiratory illness. The studies show that, in the global average, urban heat islands saved four times as many lives in the winter as were lost in the summer. In cold climates, it was 11 times as many! Tropical cities may not enjoy these benefits – since their winters are not cold enough to kill. But overall, this suggests city planners should adapt regionally to urban heat islands. Warmer cities should try to mitigate heat effects... while colder cities may want to encourage them! Cities that experience both temperature extremes – and many do – may investigate changing roof colors and other flexible solutions that could reflect heat in summer, and absorb it in the winter. Changing, like nature, with the season.
August 4 · 2 min
Urban Heat Islands
Summer in the city. It’s sweltering. The sun beats down all day. Its heat is absorbed by concrete buildings and blacktop, which hold that heat at night -- and into the next day. The heat builds over weeks and months, keeping summer city temperatures much higher than their surrounding suburban and rural areas. Cities can be 10 degrees Fahrenheit hotter, or more! That’s what’s called an urban heat island. People respond by turning down the thermostat on their air conditioning. Exhaust from AC units and heat from nearby power plants further warm the air. The increased electric load can lead to brownouts, or blackouts. And if people lose power, and air conditioning – or if they don’t have it to begin with – the high urban temps can be deadly. Thousands of people in normally temperate cities in Europe and Asia have died over the past years in summer urban heat waves. So, city planners are working to cool these heat islands. Methods can include so-called ‘cool roofs,’ which use white paint or reflective materials to radiate the sun’s heat, rather than absorb it. Cool roofs can reduce indoor building temperatures by a few degrees Fahrenheit. Green roofs, planted with gardens or even trees, can double that reduction. Likewise, creating more urban green space cools cities, as plants give off water vapor to provide evaporative cooling to their leaves, and the air. Remarkably though, these deadly heat islands may save more lives than they’re endangering – and we’ll talk about that on another EarthDate.
June 30 · 2 min
Mining, Past and Present
Today we make stuff in three ways. Plants and animals make our food, wood and fiber. Oil and gas make plastic, fuels, chemicals and clothing. And rocks, dug out of a mine, become metal, concrete and stone – which make our buildings and roads, planes, trains and automobiles, energy infrastructure and much more. By weight and value, our most important mined product is coal – which makes about 1/3 of global electricity. Coal was also the first thing humans mined at scale, 20,000 years ago in South Africa. Around 6,000 years ago, we figured out how to smelt metal out of ore. Copper, gold, silver, tin and iron shaped civilizations in the Bronze and Iron ages, making weapons and tools, art and currency. Today, we mine in several ways. Surface mines dig out shallow ore deposits or stone. Underground mines dig tunnels to reach deeper reserves. Placer mining separates minerals from erosion runoff. Solution mining dissolves minerals in place with a solvent, which is then pumped to the surface and purified. All forms of mining have environmental impacts. Surface mines can deforest large areas and disrupt ecosystems. Waste rock, and polluted water and air can impact local communities. In another EarthDate, we talk about ways to address these impacts, as we ramp up mining to meet the demands of new technology.
June 30 · 2 min
Mining, The Future
In another EarthDate, we talk about how mining provides the materials to build the modern world. But new technology is changing that world. We’re building huge new data centers for AI; batteries to power EVs, and stabilize the power grid; and enormous volumes of solar panels and wind turbines. All these will require a lot more mining. And all mining impacts the environment. So engineers are working to make the process cleaner and safer. Mine tailings – the waste rock – are today kept in huge ponds, which can spill catastrophically. New techniques dry them out for safer storage, or to use as construction materials, and recycle the water. And more mines are capturing, treating and reusing water throughout their processes. Many mines are working to reduce emissions at the site, switching diesel equipment and trucks for electric motors, requiring more electricity. More advanced automation makes mines more efficient. More advanced exploration uses less energy and disturbs less land to find new resources. New technologies extract lithium directly from hot, deep brines. And use electricity, instead of high heat or strong acids, to separate metals from mining waste. Meanwhile, improved recycling programs recover more copper, lithium and other metals from old electronics, batteries and scrap, to help reduce the need for new mines. And we talk about that, on another EarthDate.
June 30 · 2 min
Urban Mining
On another episode, we talk about how mines have a large environmental footprint. Think of a giant pit, with huge machines digging out ore. By contrast, think of your old smart phone. In one ton of discarded phones there’s 80 times more gold than in one ton of ore. Electronic waste, like phones and computers, contains gold, silver, palladium and rare earth elements. Old batteries contain lithium, cadmium and other heavy metals. Construction and demolition debris contains copper from piping and air conditioning, and steel from rebar and beams. Old cars and trucks contain steel, aluminum and other metals. This can make cities a repository of metals more concentrated than any mine. And makes this waste the resource for a new industry called ‘urban mining.’ The challenge is gathering that varied waste from across the urban environment, then sorting and disassembling it to be processed. That takes energy, time, labor and money. But new recycling programs, often powered by AI, sort materials with magnets and robots, then use mechanical shredders and chemical solvents to break them down into simpler components. Producing metals this way uses less energy and water than mining and processing new ore, with potentially less environmental impact – while also reducing the need for new metals, sometimes imported from unfriendly countries. In the future, more metal will come from these sources much closer to home.
June 29 · 2 min
The Water and Energy Link
Our modern supplies of water and energy are miraculous – and tightly interlinked. Only 3% of Earth’s water is fresh. And 99% of that is frozen in glaciers or stuck underground. That means just 1% of fresh water is on the surface where we can easily access it – for agriculture, mining, industry and our consumption. To get that water to us requires energy. First it’s pumped, sometimes over long distances, from a reservoir or river to a water treatment plant. There, it’s filtered, purified and chlorinated. It then flows to our houses and factories. When we’re done with it, it goes into a wastewater treatment system, where it’s cleaned again and discharged. Because water is heavy, moving it through these processes can consume 40% of a city’s electricity. And to make all that energy requires – yes – water. Oil and gas wells use water, in drilling mud and to fracture rock. Coal, natural gas, and nuclear powerplants boil water into steam to turn a generator, while water cools the plant. The generators in hydroelectric dams turn under the power of water. Even solar farms use water, to wash their panels. Wind turbines don’t use water directly, but the factories and smelters that make their parts and steel certainly do. And to get them that water… takes energy. We rely entirely on both. And couldn’t have one without the other.
June 29 · 2 min
Lakes of Life
Charles Darwin proposed that life on Earth may have started in bodies of highly alkaline water called soda lakes. New research suggests he may have been right. You might remember from a prior EarthDate that phosphorus is an essential building block for DNA, RNA, and the energy carrier for cells, ATP. Without phosphorus, there is no life. Soda lakes are some of the few places on Earth where phosphorus is readily available, rather than bound up in rocks. Nearly all these lakes around the world are closed basins. Water enters, but there is no outlet. As rivers flow toward a soda lake, running water leaches minerals out of the rocks it passes over, notably calcium and phosphorus. These then concentrate in the lake. Normally, phosphorus would bond with dissolved carbonate compounds in the lake water and sink out. But calcium bonds more readily with carbonate than phosphorus, leaving the phosphorus in a pure form. Evaporation further concentrates it. In small soda lakes, the level of phosphorus rises and falls with the rains, and the amount of river inflow. But new studies on larger closed basins show that phosphorous concentrations can remain high year-round, indefinitely…
June 29 · 2 min
Light Speed Under the Sea
In 1858, Queen Victoria sent a telegraph to U.S. President Buchanan, via the first undersea cable. The cable worked for just a few weeks, but it launched an international cable network that still dominates global communication. We think we live in a wireless world. But it’s just the short hop from our phones and wifi to a receiving antenna. Nearly everything after that is transmitted by cable, on land and undersea. Undersea cables made of copper served the world for more than a hundred years. Then, in 1988, the first fiber-optic cable was laid. They’re made of strands of ultrapure glass, no thicker than a human hair. Hundreds of strands are bundled together and protected by braided metal and nylon, jacketed in plastic. At one end, electrical signals are converted to light by a laser, then shot down the fiber-optic cable, sometimes more than a thousand miles, between countries and continents. In the shallows, they’re buried in trenches to protect them. In deep water, they’re simply laid on the seabed, which is less expensive, but exposes them to harm. There are now thousands of subsea fiber-optic cables, stretching almost 1 million total miles, transmitting 95% of international internet and voice traffic. And more cables are being laid each year. So next time you make an international call, pause for a moment to imagine your voice rocketing along at the speed of light, under the sea.
June 28 · 2 min
The Moth with Two Maps
The giant bogong moth has a brain one-tenth the size of a grain of rice. And eyes the diameter of a human hair. Yet it can navigate by sensing the magnetic field of Earth. Or by gazing at the stars, reading a mental map that it was somehow born with. Each spring in Australia, they leave the lowlands by the millions, and fly at night over terrain they’ve never seen before, following their internal compass, and that inherited star map. They’re the only insects we know of that can navigate this way. And they’re all headed to the same place: the cool highlands of the Snowy Mountains, where they sleep away the summer heat in caves. Historically, they’ve been a keystone species here, with a disproportionately large effect on the ecosystem. Other animal populations have relied on their annual arrival for food. Aboriginal tribes used to gather in the mountains to harvest and roast moths. But the bogong has declined precipitously over the last decade. Rising temperatures and drought have reduced their food sources. Pesticides have reduced their numbers. Light pollution from towns and farms has reduced their ability to navigate. Conservation groups are trying to save the moth, but with so many stressors on their population, that’s hard to do. Let’s hope they’re successful, because the bogong moth is another overlooked example of the wonders of nature, its interconnectedness, and its vulnerability.
June 28 · 2 min
The Crystal Eye of Ninevek
During World War 2, an American pilot flying over the Canadian arctic saw something extraordinary. A midnight blue lake, 2 miles across, shaped in a perfect circle. The Allies kept it a secret, using the lake as a navigation landmark during the war. But in 1950, photos hit the media, and the lake became a sensation…because it shouldn’t exist. There were no rivers leading into it, and none leading out. There was not enough liquid groundwater in this frozen landscape to fill it. It was as if the lake had been dropped from the sky. And in fact, it had. Scientists soon determined it was formed by a huge meteorite. Its trajectory would have been straight down, striking Earth at 30,000 miles an hour, with the force of 8,000 Hiroshima bombs. It bored a hole more than 800 feet deep, and pushed up 500-foot high ridges around it, isolating it. Of course, the natives had known of the crater for centuries, calling it the Crystal Eye of Nunavik -- because it contains some of the clearest surface water on Earth. Research confirmed that the water came from melting Ice Age glaciers and is only recharged by melting snow and ice. With no rivers to bring in sediment, the soils on the lake bottom contain mostly dust, pollen and diatoms -- from millennia ago, preserved in the frigid water. In this way, the Crystal Eye literally lets scientists “see” into the distant past.
June 28 · 2 min
We Changed Horses
Horses changed human history. But first we had to change horses. The horse evolved in North America 50 million years ago, and migrated across the Bering land bridge into Eurasia. Then, during the last Ice Age, it went extinct in the Americas. Around 5,000 years ago, humans began taming horses in the Eurasian Steppe, in what is today Kazakhstan, Russia and Ukraine. There, archaeologists have found residue of mare’s milk in drinking vessels. Some horse skeletons show wear on their teeth suggesting they held bits in their mouth. But other skeletons have arrow points embedded in bones, suggesting that horses were hunted as much as domesticated. A thousand years later, a different steppe culture tamed a different horse and, evidence shows, developed a horse culture – so successfully that it replaced the earlier horses. Genetic testing revealed that this first domesticated breed, called DOM2, became the progenitor of all later horse breeds. With them, humans could travel farther and faster than ever before. Mounted nomads could cover landscapes. Mounted cavalry could vanquish enemies. Horses could pull carts, and later, plows. We hardly think about it today, but from 4,000 to just 100 years ago, horses were the driving force in human transportation, settlement and warfare. The only thing that moved more people was our own two feet.

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