EarthDate

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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.

  1. 19 HR AGO

    True Blue

    We call Earth the Blue Planet because it’s covered in water—but what makes water blue? And why is it not blue in your glass or your ice cubes? Water has many rare properties, some of which we’ve covered on previous episodes. But this property, its blueness, is unique to water and goes right to its core. It’s the only molecule in the universe that vibrates a color. How is that? The water molecule is made up of two atoms of hydrogen and one of oxygen. The hydrogen atoms are very lightweight, but their bonds are very strong. Imagine ping pong balls connected by metal springs. It doesn’t take much to start water molecules vibrating. In basic terms, light itself is vibrating electromagnetic energy. Different colors have different vibrational frequencies. Water molecules vibrate fast enough to reach the lower frequencies of visible light, where they absorb red light, so we see the blue light that remains. This effect is too faint to notice in your glass of water. But it’s already visible in a bathtub or swimming pool, and gets more pronounced when the effect is amplified, as light passes through more and deeper water. Scuba divers know this well. Past a certain depth, blue becomes the only color—till they turn on a flashlight, which reintroduces full-spectrum white light, and all the colors appear again. There are other molecules that vibrate, but none that can reach into the visible light spectrum. Only water is true blue.

    2 min

  2. 19 HR AGO

    The Amazing Monarch Relay

    You may have heard that monarch butterflies migrate from Mexico to Canada and back. But you may be more amazed to know that the returning butterflies are the great-great-grandchildren of the butterflies that left. Here’s how that works: The first generation of monarchs leaves Mexico in the spring, pausing to breed and lay eggs as they fly northward. Their eggs hatch into caterpillars, which eat for two weeks, then metamorphose into butterflies. In four weeks, they too are flying northward. As the first generation dies, the second generation will fly on, farther north, pausing only to lay eggs of their own. Eventually they too will die, and be passed over by their offspring. This third generation will finally reach Canada, where they’ll lay eggs. But the fourth generation that comes from them will be genetically different. The shorter days and colder temperatures cause these butterflies to develop much larger fat stores, making up a third of their bodies. And their reproductive organs remain undeveloped—since their purpose is not to breed, but to fly. Before winter arrives, they’ll make the entire 3,000-mile journey to Mexico—where they’ll seek out the same mountaintops as their great-great-grandparents. They’ll roost in the same fir trees, congregating in huge masses to hibernate through winter. In spring, their reproductive organs develop, and they’ll begin their own flying, mating, egg-laying journey, to start the amazing monarch relay, all over again.

    2 min

  3. 19 HR AGO

    Iceland, the Geothermal Pioneer

    Deep within our planet, intense heat left over from Earth’s formation is stoked by the continued decay of radioactive isotopes. In a few places, like Iceland, geologic features allow this heat to come close to the surface. Here, it often turns groundwater to steam. For a century, Iceland has been tapping into this naturally occurring steam and using it to heat the homes, streets and sidewalks of Reykjavik. Or to run power plants to make electricity. Now, Iceland is trying to take it a step further. Scientists are drilling experimental wells, nearly 3 miles into the earth, to try to tap into superheated water. At what’s called supercritical temperatures, above 750 degrees Fahrenheit, water and steam merge into a single supercritical fluid, which behaves differently than either. A typical Icelandic geothermal steam well produces the equivalent of 5 megawatts of energy. A supercritical well could produce 10 times that. This means that just three or four wells could heat an entire city. Of course, this is a very challenging prospect. At such high temperatures and pressures, supercritical fluid is very hard to handle. Iceland shut in its first successful well after a valve failure. But the massive amount of energy on tap could make this a promising energy source—in those rare, lucky places where supercritical water is near enough to the surface to access.

    2 min

  4. 1 DAY AGO

    Atmospheric Rivers

    Previously, we talked about California’s 1861 super flood that turned its Central Valley into an inland sea. That flood was caused by an ARkStorm. The A R in Ark stands for Atmospheric River. Atmospheric rivers are layers of water vapor that form in the tropics and circle the globe. They’re very large—up to 2 miles high, 500 miles wide and 5,000 miles long. Each can carry 15 times the flow of the Mississippi River. Atmospheric rivers are always forming, and always flowing—until they hit something like a mountain range, that forces them up into the colder atmosphere, where they condense into rain. In this way, they provide 90 percent of the rain in the mid-latitudes, and up to 50 percent of California’s. But they can also bring extreme floods. Sedimentary records show this has happened in California 10 times in the last 2,000 years, suggesting that California is due for another one. Since the 1861 flood, the state’s population has increased more than 100-fold. Millions of people now live in areas vulnerable to droughts, fires and floods. Scientists predict an ARkStorm could flood a quarter of California homes, cause one and a half million people to evacuate, and leave almost a trillion dollars in damages. A California super flood is as likely as a super quake but could be three times more devastating.

    2 min

  5. 1 DAY AGO

    California’s Super Flood

    California is well known for droughts. But it also had one of the greatest floods in U.S. history. In 1861, California had been in drought for 20 years. Most of the state’s residents lived around San Francisco and in the Central Valley. Ranchers there had been praying for rain for two decades. In November, they finally got it. First, winter came early, bringing heavy snow to the mountain range that bounds the valley. In December, temperatures rose, the snow melted and drained into the valley, saturating the soil. Then the rains came—and didn’t stop for 43 days. Wave after wave of storms rolled in from the Pacific, bringing more than 10 feet of rain and snow. Creeks became rivers, sweeping entire towns away. Rivers jumped their banks and cut new channels. But much of the water was trapped in the Central Valley, which became an inland sea, stretching 300 miles north to south, in places 60 miles wide. It took six months for this inland sea to evaporate and percolate into the ground. But the flood had destroyed a quarter of California’s taxable property and almost forced the state into bankruptcy. It also wiped out nearly 1 million livestock animals, prompting the Central Valley to move away from ranching to become the agricultural powerhouse we know today. Superstorms like this come along every 150 to 200 years, and we’ll talk more about them on a future EarthDate.

    2 min

  6. 2 DAYS AGO

    Preserving with Salt

    Human life has always depended on salt. Chemically, and culturally. All animals need it for the function of blood, organs, muscles and nerves. Carnivores get it from eating other animals. Herbivores get it from salt licks and minerals in groundwater. For millennia, humans have used salt to preserve meat—and still do today. This works because salt, in abundance, kills bacteria. When we pack meat in salt, it draws water from the cells. Water naturally moves across cell membranes to try to reach an equilibrium of saltiness on both sides of the membrane. This process dehydrates the meat, making it inhospitable for bacteria and parasites, which need water to live. Culturally, salt has been equally important. Salt-preserved meat and fish were crucial to our exploration of the globe, feeding sailors as they crossed oceans, and sustaining remote communities. Wars were fought over salt, and access to it could influence the outcome. As recently as the American Civil War, Union troops captured Confederate salt mines to limit their food supply and force them to the coasts to get salt—where they could be more easily attacked. Settlers in the West often followed game trails to and from brine springs or salt outcrops. These became cattle trails, then wagon paths, then roads, sometimes even the highways of today. Salt has literally shaped the course of human history.

    2 min

  7. 2 DAYS AGO

    Floating Rocks

    Recently, a group of sailors in the South Pacific encountered something extraordinary. One minute they were sailing in water. The next, in a sea of rocks. Floating rocks, some the size of basketballs, as far as the eye could see. Imagine their amazement! Turns out the rocks were pumice, which was extruded by an undersea volcano near the island of Tonga. Pumice is molten rock filled with gas bubbles, ejected at high pressure like whipped cream from a can. When it hits the seawater, it hardens instantly, trapping the gas within it, making a rock that’s lighter than water. The pumice then floats to the surface where it forms huge rafts of rocks, from pebble size to much larger. They’ll float until wave action breaks up the rocks as they grind against each other, or they get waterlogged and sink. These rock “rafts” form only about twice per decade but can be enormous. In 2012, one formed off the coast of New Zealand that was 300 miles long. The raft from Tonga was the size of Manhattan and was floating toward the Great Barrier Reef. The surface of pumice is rough, full of craters and crevices, making it perfect for mollusks, corals and other sea creatures to attach themselves for the ride. Scientists think that pumice rafts like these have helped life-forms cross open oceans and start new colonies in new places. Much the way humans did on rafts of our own making.

    2 min

  8. 2 DAYS AGO

    Plight of the Pangolin

    The pangolin is one of the world’s most unusual animals—and one of the most heavily poached. An adult pangolin is 3 to 5 feet long and eats some 70 million ants and termites a year, using a tongue that’s longer than its body, covered in sticky saliva. It burrows into termite mounds and anthills and can close its ears and nostrils to keep angry ants at bay. That may sound like an anteater or an aardvark. Except, the pangolin is completely covered in scales. It’s the only mammal that has them. These scales are made of keratin, just like our fingernails. A single pangolin could have more than a thousand, making up 20 percent of its body weight. Pangolins roll into a ball when threatened—the sharp edges of their scales providing extra protection, even against lions. But that’s not enough to keep human predators away. The pangolin’s scales are valued in Asian folk medicines, even though they’ve been proven to be no more medicinal than an old toenail. Their meat is eaten in Asia as a delicacy. Even their blood is considered an aphrodisiac. So, poachers catch and kill them, which has made all eight species critically endangered or vulnerable. In the last 10 years, customs agents have confiscated literally tons of pangolin scales, which came from more than 1 million animals. World Pangolin Day is February 15. You probably don’t buy pangolin products yourself, but raising awareness for this remarkable, gentle animal can support its protection.

    2 min
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About

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.

Information

  • Creator
    Switch Energy Alliance
  • Years Active
    2K
  • Episodes
    154
  • Rating
    Clean
  • Copyright
    © Copyright 2026 EarthDate
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