EarthDate

Recently, scientists discovered the fossil of a hadrosaur, a duckbilled dinosaur, which was bitten by a Tyrannosaurus. A bite on a fossil is not that unusual, but this one helped settle an argument. Over the past few decades, some paleontologists maintained that T. rex was a ferocious hunter. Newer theories pointed to his useless forelimbs, small eyes, and huge olfactory chambers. He wouldn’t have been able to grasp prey and may have had poor vision—but he would have been able to smell a rotting carcass from miles away. In other words, he was likely a scavenger. But the hadrosaur tail vertebrae in this fossil were fused together around a T. rex tooth—the wound had healed. This meant that the hadrosaur was alive when it happened, and lived on. Which strongly suggests that T. rex did in fact chase and catch it—almost. This brought up another question: given his weaknesses, how did the tyrannosaur do it? A different set of scientists analyzed the leg mechanics of T. rex for bone stress. Proponents of “T. rex the hunter” had pointed to his speed, previously estimated at over 30 miles per hour. But this new research suggests that the foot bones, carrying his 7 tons of weight, would have shattered at that pace. The tyrannosaur’s top speed was probably just 12 miles per hour. And maybe that’s why the duckbill got away—T. rex may have been an occasional hunter, but maybe not a very good one.

Earlier, we talked about the run-up to the greatest natural disaster in American history, the Dust Bowl. Between 1870 and 1920, settlers poured into the Great Plains, plowed under native grasses, and planted grain. Then in 1929, the Great Depression struck, and grain prices collapsed. In 1931, a long drought set in. Farms failed across the region. Millions of acres, stripped of grass and barren of crops, lay untended. The fierce prairie winds carried the dry topsoil high into the sky in roiling storms of black dust that pummeled farmers and buried buildings. In 1933, a storm like this came nearly every week. In 1934, the dust clouds expanded to cover the Midwest. In 1935, a blizzard of hot, black soil raced across the country at 100 miles an hour, cutting visibility to three feet and blanketing Washington, D.C. By then, nearly a billion tons of fertile topsoil had been carried off the Great Plains. The human toll was staggering. More than 3 million people abandoned their farms and businesses and left the Plains, penniless. Those who stayed suffered: respiratory diseases from breathing dust, hunger so severe they had to eat tumbleweeds. Infant mortality soared and birth rates dropped to the lowest in U.S. history. What finally ended the Dust Bowl? We’ll see, in our next and final installment of this story.

The greatest environmental disaster in American history lasted for eight years and displaced more than 3 million people. What was it? The Dust Bowl—which refers both to this event and the place where it happened: some 100 million acres in Kansas, Colorado, Oklahoma, New Mexico, and Texas. This area normally sees just 20 inches of rain a year. High winds from the Rocky Mountains roll across it. Summers bring scorching heat; winters bring Arctic blasts from Canada. Explorers called it the Great American Desert and avoided it. But in the late 1800s, agents from the government, eager to push development westward, rebranded it “the Great Plains.” Anyone with an $18 filing fee could stake a homestead. People came in droves and found an ocean of native grasses. These grasses had developed to withstand the prairie’s harsh conditions. Over thousands of years, they created the topsoil, held it in place against the wind, and trapped moisture to withstand periodic droughts. But to the inexperienced farmers, it just looked like grass. They burned it or plowed it under, and planted wheat and other crops. Grain production soared and the expansion seemed a success. Over the next 50 years, millions more settlers arrived. Then, in 1929, the Great Depression hit. Grain prices collapsed. Worse, in 1931, the rains stopped. What followed was a disaster of epic proportions, which we’ll cover in our next installment on the Dust Bowl.

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.

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.

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.

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.

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.

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.

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.

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.

Each year, millions of pebble-sized meteors strike Earth’s atmosphere and burn up harmlessly. But once a century, a house-sized meteor makes contact—and explodes in the air with devastating results. In 2013, one such airburst occurred in Russia. The Chelyabinsk meteor broke apart miles above the surface, with 30 times the force of the Hiroshima atomic bomb. It blew out a million windows over 200 square miles and injured 1,600 people. In 1908, near the remote Russia-Mongolia border, a larger airburst occurred. Scientists who arrived on the scene found it had flattened 80 million trees over 800 square miles. Events like this happen every millennium, and in 1700 BC, there was an even bigger one. North of the Dead Sea, in what is now Jordan, 50,000 people were vaporized in an instant. A flash of extreme heat, over 7200 degrees Fahrenheit, disintegrated houses, melted sand and stone, and turned pottery to glass. A tidal wave of boiling saltwater swept inland, poisoning the soil. The area, which had been continuously inhabited for 2,500 years before that, lay desolate for 600 years after. Since the Chelyabinsk meteor in 2013, NASA initiated a program to identify and track objects within 5 million miles of Earth that could enter our atmosphere and cause an airburst.

Getting caught in quicksand can be fatal, with victims dying mostly from dehydration, hypothermia or heat exhaustion. What can you do to avoid getting trapped—and to escape if you do? It starts by knowing where quicksand forms and what it looks like. Quicksand is just super-saturated sand. Normal wet sand is about 25 percent water; quicksand is more than 70 percent. Quicksand can form on beaches, tidal flats, riverbanks or near springs—anywhere the ground is saturated with water. In those places, look out for sand that’s spongy or rippled in appearance, and check suspicious areas with a stick. Quicksand looks solid, and if you were to place something or even step lightly upon it, it may support you. But step firmly and the quicksand will liquefy, and you’ll sink. Because humans are buoyant, we typically won’t sink below the waist or mid-chest. But once the sand grains are out of liquid suspension, they too will sink, and compact around your legs, trapping you. The more you struggle, the more sand will liquefy and sink, and the more trapped you’ll become. The key to getting out is to remain calm. Lie back in slow motion. Wiggle your legs in tiny movements, which will slowly let water in to loosen the compacted sand. Then gradually recline to float on the surface. Once free, you can slowly crawl or swim to the edge and roll onto solid ground.

Opinions are divided on eucalyptus trees. In some places, they’re a fast-growing cash crop. In others, they’re an invasive species. In Australia, where the trees originate, they’re about to become more popular because they may lead miners to gold. In Australia’s dry climate, eucalypts send roots down hundreds of feet looking for water. In gold mining areas, scientists have found microscopic gold flakes, thinner than a human hair, in the tissues of their leaves and on the waxy residue that coats them. They wondered if blowing dust could have carried gold particles onto the trees or if perhaps their deep roots could have drawn up trace amounts from far below the surface. They conducted experiments, growing eucalypts in sterile environments, giving them gold-laced water. And sure enough, gold appeared in the foliage. They realized that the gold is probably toxic to the trees, which send it out to their leaves where it can be shed. The scientists analyzed eucalyptus trees in other parts of Australia but found very little gold. Clearly, trees in gold-rich regions were mining it themselves! Before we get too excited about processing eucalyptus leaves for gold, it would take 100 trees to produce enough for a wedding band. Scientists do believe, however, that searching for trace amounts in eucalyptus leaves could be a low-impact way of prospecting for gold in the future.

Mass extinctions have happened throughout Earth’s history, sometimes wiping out the large majority of all life on Earth. Each spelled the end for millions of species—and the beginning for millions more that evolved to take their places. On earlier EarthDates, we talked about the asteroid that smashed into Earth, ending the reign of the dinosaurs while opening the door for mammals. But there was an earlier event that appears to have created the same opening for dinosaurs themselves. Around 250 million years ago, dinosaurs made up only about 5 percent of animals on Earth. Then a massive series of volcanic eruptions filled the atmosphere with carbon dioxide, which triggered dramatic global warming and extreme global rainfall. The rain caused floods across the planet for many thousands of years. Floods alternated with periods of drought for 1 to 2 million years, to create an era so severe it earned its own geologic name: The Carnian Pluvial Episode. It stressed all life on Earth, plants and animals, and removed many species that were poorly equipped for the harsh conditions. By 2 million years after the Pluvial Episode, dinosaurs, who were better adapted for these conditions, exploded in population and variety, with new species filling empty environmental niches. What happened for the dinosaurs, then happened to the dinosaurs—and it will happen again. In this way, life on Earth renews itself.

In 1911, Robert Scott and Roald Amundsen led expeditions to Antarctica, both hoping to be first to the South Pole. Amundsen’s crew left 20 days before Scott, using sled dogs. Scott’s team took a different route, using motorized snow tractors, hoping to speed their passage. After 77 days, Scott and his men finally reached the pole—only to find that Amundsen had beat them to it. With great disappointment, they turned back to their ship … when disaster struck. The temperature plummeted as the Antarctic winter arrived early. In their journals, they recorded temperatures below -40o Fahrenheit. Weather kept their base team from provisioning their return depots. Out of fuel, they had to pull sleds with their tents and gear. In the extreme cold, the ice was no longer slippery—we talked about this in a previous EarthDate. A layer of water less than one-billionth of a meter thick occurs on the surface of ice down to -36o Fahrenheit. Below that, the water molecules become pinned to the ice and they no longer slip. This meant that Scott’s sleds no longer slid, slowing their progress and doubling their exposure to the severe cold. One by one, the men got frostbite and could no longer travel. Out of options, they made their last camp, wrote farewell letters, and waited for the end. A trip cut tragically short by the not-so-slippery properties of ice.

Once an ice skater gets going, friction between her skate and the ice creates a microscopic layer of water that allows the skate to hydroplane. But before she can get up to speed, and friction can melt the ice, it’s still slippery enough for her to start her glide. Why is ice so slippery? In the 1800s, scientist Michael Faraday conducted experiments to show that ice, even well below freezing, has a very thin layer of water on its surface. But the technology to see this layer did not exist. Nor did the scientific understanding to prove that it was there. It would be more than 100 years before scientists could finally see Faraday’s water layer using X-ray imaging. And still later that they could measure it. Turns out this thin layer is very thin indeed—thousands of times thinner than a sheet of paper. In fact, it’s just a couple of molecules thick. When water freezes, its molecules interlock tightly to create the crystalline structure of ice, held together by four hydrogen bonds. But the molecules on the surface of ice can only bond to the molecules just beneath them, with just three hydrogen bonds. This won’t allow a stable crystalline surface. This strange, disordered molecular state of water on the surface of ice will persist down to -36o Fahrenheit. But if the temperature goes below that, ice will no longer be slippery—sometimes with disastrous results, which we’ll talk about on another EarthDate.

At midnight, at the end of the year, Earth celebrates the completion of two cycles. The first, of course, is Earth’s rotation, turning day to night and back again. To complete this cycle, Earth rotates at 1,000 miles an hour, counterclockwise. Not all planets spin this way. Venus rotates the opposite direction, and Uranus spins at 90 degrees to its orbit. But pretty much everything in the universe spins. The second cycle of course, is Earth orbiting the sun. The Solar System began as a cloud of dust and gas spinning around the sun 4.6 billion years ago, and should keep spinning for a few billion years more. This rotation of Earth around sun is even faster: 67,000 miles an hour, and it takes 365-and-a-quarter days. This was recognized and set into a calendar by the Romans, but they overlooked that extra quarter day. Meaning that, by the late 1500s, the calendar had drifted 10 days off. At that point, Pope Gregory added a leap day every 4 years, and the modern calendar was born. Our Solar System is moving, too, and faster still. It’s in the Orion arm of the Milky Way galaxy, which orbits a supermassive black hole at 600,000 miles an hour. And the black hole is spinning, too, even faster—more than 1,000 times a second. So, if the New Year has your head spinning, well, now you know why.

Maybe only Santa’s reindeer can fly—but regular reindeer come pretty close. They can fly over the tundra at 50 miles an hour, covering more than 20 miles a day. Their annual migrations span 3,000 miles, the longest of any land animal. And they’re spectacularly adapted for that life: Their eyes change color depending on the season. In their summer above the Arctic Circle, with nearly 24 hours of sun, their eyes turn gold, to reflect the harsh light. In the dark months of winter, their eyes turn blue, to let in as much light as possible. Their eyes also can see ultraviolet light. This makes the snow even brighter, but against it, some important things appear black: The fur of predators, who might otherwise be camouflaged. And lichen, the reindeer’s primary winter food. What their eyes can’t see is red. Like many mammals, they’re red–green colorblind; both colors appear brown. While this would have made it hard to follow Rudolph’s nose, their noses are pretty amazing in their own right. They’re lined with capillaries, to warm the frigid air before it enters their lungs. They’re also the only deer species where both males and females grow full antlers. The males’ drop off after mating season ends in November. But the females’ stay on through winter, into the spring calving season. This means that if Santa’s reindeer do, in fact, have antlers on Christmas Eve, they’re all females.

There are over 1 million avalanches every year, but they kill only 150 people. So, while it’s very unlikely you’ll get caught in one, here are a few safety tips, just in case. Avalanches happen when a slab of unstable snow breaks off from the layers beneath it. If you’re on top of that slab when it happens, ski or run for the sides. Same thing if you’re in its path. Avalanches can reach 80 miles an hour in 5 seconds, and top 120 miles an hour. You won’t be able to outrun it, so head for the sides to get out of the way. If you do get caught in it, swim against the snow to try to stay on top. Humans are heavier than the moving snow, so we tend to sink into it. When the avalanche stops, there will be a brief period when the snow is still loose. If you’re disoriented, spit. That’ll tell you which way is down. Then try to dig your way up and out. If you can’t, carve a breathing space, as large and as quickly as you can. The weight of the snow will soon compress and harden it, restricting your movement. Try to remain calm, to conserve your energy and your oxygen. The most important tip is to be prepared before you head into the mountains. Take an avalanche beacon, which can transmit a signal to rescuers. Let friends know where you’re going. And check with local authorities to avoid avalanche areas in the first place. Because the best way to survive an avalanche is to not get caught in one.