Episodes

There’s one source that provides almost a third of the water for all US agriculture. It’s called the Ogallala aquifer, stretching under the Great Plains from South Dakota to northern Texas. Once considered inexhaustible, we now understand its limits. For the first settlers in the Great Plains, water was scarce and farming was difficult… Until the 1850s, when they began to use windmills to pump up groundwater from the aquifer. Suddenly they had all they needed and an agricultural boom was on. ...

Tiny mosses were the first land plants to evolve on Earth. But the first real plants, the big leafy kind, came on the scene 400 million years ago—200 million years before hardwood trees and flowering plants. I’m talking about ferns. They flourished, then and now, through a unique two-stage life cycle. Mature ferns produce spores that drop to the ground. There they grow into gametophytes, which don’t look anything like the mature example. In some species, they grow underground. The gametophyt...

It may surprise you to know that one of the most important minerals in history has been … potash. Many centuries ago, humans discovered that if you took a pot, put in wood ash, boiled it then strained out the residue, you’d get potash—which had two very special qualities. First, when mixed into soil it made an excellent fertilizer for crops. Second, when mixed with sulfur and charcoal it made gunpowder. Potash was so valuable that the very first U.S. patent, signed by George Washington himsel...

Some very old oyster shells found in a cave have answered the eternal question, “who was the first person to eat that”?! Looks like it was a hungry South African, 164,000 years ago. Today, we consume around 8 billion oysters a year. But they’re good for so much more than eating. Oysters cement themselves together to form reefs that control coastal erosion and reduce wave energy. These reefs increase the surface area 50 times compared to a flat ocean bottom, providing habitat for many other sp...

Only one ten thousandth of Earth’s total water supply is fresh water on the surface, to keep billions of humans and other animals alive. Good reason to conserve it—which also saves energy and money. Water is heavy, so it takes energy to move it. The farther it’s pumped in pipelines or carried in trucks, the more it costs the user. Water purification systems also require energy, adding to the price. Sending more water down the drain increases the volume that must be processed to use again, incr...

The word monsoon may conjure in your mind torrential rains. But monsoon actually comes from the Arabic mawsim—meaning not rain but season. In the tropics, there are only two seasons, known as dry and wet monsoons. They’re brought about by equatorial winds that blow in each spring and fall—predictably enough that sailors have depended on them for centuries. During wet monsoons, the winds bring rain in tropical places around the world, like India and Southeast Asia. But also in the subtropics—li...

The meteorologists who invented weather radar never expected to be studying bugs. But today they do. There are 159 weather radar stations in the US. They look like giant golf balls on towers. There’s a rotating dish within the white sphere that sends radio pulses into the sky. When they meet something, some of the radio waves bounce back. The radar reads the time and strength of the returned waves to determine the distance and concentration of the object they encountered. Like a cloud. As wea...

A recent discovery has reshaped our understanding of human history in North America. A few EarthDates ago, we talked about a tribe of Siberians who were stranded in the Bering Strait for centuries before migrating into North America to become its first citizens 16,000 years ago. Turns out, they weren’t first. Because in White Sands National Park, scientists have found something remarkable. Modern visitors to this dry southeastern corner of New Mexico, who happened to come during one of its ra...

At the bottom of one of Africa’s deepest lakes lies a secret that could put two million nearby residents in danger. Lake Kivu sits along the East African Rift Valley, where the tectonic plates that bisect Africa pull apart. Volcanoes leak natural carbon dioxide into the bottom of the lake, where the water pressure is high enough to dissolve and concentrate the gas in water. If the water temperature changes, or the water column is overturned, the CO2 can suddenly turn to gas again and shoot to...

The Andean Condor is a giant vulture that lives along South America’s west coast. It’s one of the heaviest flying birds in the world, weighing more than 30 pounds. Yet it can stay aloft for hours at a time. How do condors do it? Efficiency! The condor launches itself from a high peak or cliff, spreads its massive wings—the largest in surface area of any living bird—and soars. It will then ride thermals, currents of hot air rising from the ground, scanning the land below for carrion to scaveng...

Gold is malleable, portable, nontoxic, beautiful and rare. Those qualities have made it an excellent currency over the centuries. But there’s another metal with all those properties and more—and it’s much more valuable. It’s called rhodium, part of the platinum group of metals. The name comes from the Greek rhodon, meaning rose, for the rosy color of rhodium compounds. It’s abundant in other parts of the universe but vanishingly rare in Earth’s crust—just one part in 200 million. We mine 100 ...

In 1836, Charles Darwin and his colleague Joseph Hooker visited Ascension Island, really just a barren pile of volcanic basalt topped by an old cinder cone, ironically named Green Mountain. There were very few plants, but some soldiers had successfully grown a vegetable garden in the volcanic soil. This gave Hooker a crazy idea. He contacted his father, the director of the botanical garden in London, and persuaded him to send plants. Hooker and Darwin believed that if they could establish a th...

Fireflies are sometimes called lighting bugs or glowworms. But they’re not flies, bugs or worms—they’re beetles, with a marvelous capability. They move oxygen through a tube in their abdomen to combine it with a special pigment called luciferin to produce bioluminescence, the familiar glow that gives fireflies their name. There are 2,000 species of firefly around the world and 170 in the US. Different species produce different colored light, from bright red to fluorescent green. And they flas...

Microscopes, telescopes and lenses. Smartphones, laptops and televisions. Mirrors, windshields and cathedral windows. None would be possible without glass. It’s made of silicon dioxide, or quartz, that’s melted and then cooled so fast that crystals can’t form, which gives glass its most important quality today: transparency. But glass was first valued for the way it breaks. Early humans found naturally occurring glass— from volcanoes or when a meteor superheated desert sand—and used its broke...

Scientists have a new way to measure rain, or rather, rain intensity. They looked at data from 185 weather stations across the globe, from 1999 to 2014, to determine how much rain fell in how many days. They found that, on average, one twelfth of an area’s rain falls in its single wettest day, one eighth in its wettest 2 days, and half in just 12 days. They decided to standardize this metric—the number of days it takes for half the rain to fall—as a way to gauge rain intensity in an area. Th...

We’re all familiar with those violent shaking events we call earthquakes. But it may surprise you to know that Earth more often moves without quaking in what’s called a slow or silent slip. It sure surprised scientists: they discovered this just 20 years ago. Earth’s tectonic plates began to move over a billion years ago. Their constant motion has formed, pulled apart, and slowly destroyed continents for millennia. Each tectonic plate rotates around an axis, while its edges collide with, slide...

Landslides happen when a slope becomes unstable—because of denuding, from a fire or deforestation; over-steepening, from erosion or mining; overloading, from a reservoir or heavy snowpack; or oversaturation, with rain or melt water. So many things can cause a landslide that they happen in every U.S. state and nearly every country. When the slope gives way, soil can speed downhill at 50 to 100 miles an hour, carrying trees, boulders, cars, even houses. Earthquakes trigger just five percent of ...

The South Pole is the most inhospitable place on Earth—yet, each year, around 50 brave scientists and staff endure the winter there. Outside temperatures approach minus 120 degrees Fahrenheit in constant darkness. And they better hope nothing goes wrong. Because no one can come to help them. The South Pole is 800 miles from the nearest human contact. That’s farther than the International Space Station, which orbits less than 400 miles above Earth. From research bases on the Antarctic coast, i...

There’s an Irish saying, “There’s a pot of gold at the end of every rainbow.” But it used to say, “you’re as likely to find a pot of gold as the end of the rainbow.” That’s because if you go looking for its end, the rainbow vanishes. Rainbows occur when water droplets—from rain, mist, waterfalls, even sea spray—hang in the air. When sunlight enters the droplet, some will reflect off the back side and pass again out the front. As sunlight passes twice through the water, the different wavelen...

Herbivores eat plants, and carnivores eat animals that eat plants, to get their energy. Plants and many bacteria create their own energy through photosynthesis, which depends on chlorophyll…which requires nitrogen. As we’ve described in other episodes, most nitrogen on Earth is in the form of N2, the inert nitrogen gas that won’t bond with other compounds, making it useless to plants. So, most plants rely on bacteria that cling to their roots and split the nitrogen in the soil for them. But w...

There are no snakes in Ireland. Because, according to legend, St. Patrick expelled them. True, or folk tale? St. Patrick, ironically, wasn’t Irish. Or, named Patrick. He was born Maewyn Succat in 390 AD in Britain, kidnapped by pirates at 16, and held in slavery in Ireland for 6 years. He escaped and joined a monastery in England. Then decided to return to Ireland as a missionary, where he converted Druids and built the first church. He died in 460 AD in Downpatrick, hence the name. A few cen...

In the 1800s, scientists found a 400-million-year-old fossil fish they thought could be the missing link between aquatic and land-dwelling creatures. They would have loved to study it, but it had gone extinct with the dinosaurs. Or so they thought. Until 1938, when a museum curator saw a fisherman haul one out of his net in South Africa. She wrote a hasty telegram to her museum. They wrote back: “Get that fish!” She had found the coelacanth, not extinct after all, but hiding for millions of ye...

Tornadoes are mysterious. But on this EarthDate, we’ll try to unravel a few of their secrets. You’ve probably heard there’s a “tornado season” that happens in “tornado alley.” Well, not exactly. Tornadoes can happen almost anywhere—North and South America, Australia and New Zealand, South Africa, and the Indian subcontinent, where they’re most deadly due to higher population density. And they can happen any time. Most occur within a few months…but that depends on where you are. In the southea...

700 million years ago Earth froze over completely and stayed that way for millions of years. How did this deep freeze start, and how did it end? We think it went like this: At the time, all of Earth’s land was held in one large continent called Rodinia. As it began to break up, huge areas eroded, pulling carbon dioxide from the air and sequestering it in minerals. With CO2 dropping, the atmosphere cooled, and ice began forming in the polar oceans. As the ice sheets extended, their white surfa...