Marcus Webb 
Stand on a ridge in the Appalachians and rain falling on your left boot ends up in the Mississippi, bound for the Gulf of Mexico. Rain on your right boot ends up in the Atlantic. Nothing marks the line. What is a watershed is exactly that: the land area that drains to a single common … Read more
A teaspoon of healthy soil contains more microorganisms than there are people on Earth. That is the first clue that soil is not simply dirt. What is soil, properly defined, is a porous mixture of mineral particles, organic matter, water, air, and living organisms, structured into layers and capable of supporting plant roots. Soil Is … Read more
A glacier looks like a static thing. It is not. Ice a few hundred meters thick behaves like an extremely viscous fluid, creeping downhill at a pace you cannot see and cannot ignore over a few thousand years. What is a glacier, in the strict sense, is a body of ice on land, formed from … Read more
A hurricane is a machine for moving heat from the ocean into the atmosphere. Everything else — the eye, the spiral bands, the 150 mph winds — follows from that one job. What is a hurricane, stripped to the definition, is a tropical cyclone with sustained winds of at least 74 mph. The Naming Rules … Read more
Every tornado is attached to a thunderstorm. Almost no thunderstorms produce one. That gap — thousands of storms, roughly 1,200 tornadoes a year in the United States — is the whole puzzle. What is a tornado, then, beyond a funnel in a photograph? The Definition A tornado is a violently rotating column of air in … Read more
A flamingo chick hatches covered in gray down. It stays gray for months. The pink comes later, and it does not come from genetics in any simple sense — it comes from the food. Why are flamingos pink is really a question about what happens when an animal eats paint and then wears it. The … Read more
Watch a garden spider build an orb web and the first thing that stands out is the waste. She spins a frame, fills it with radial spokes, adds a temporary spiral, then cuts the temporary spiral out and replaces it with a sticky one. The whole structure goes up in under an hour, from an … Read more
A great white can find a flounder buried in sand, in water too murky to see through, without touching it. No single sense explains that. To understand how do sharks sense prey, you have to look at a system of seven senses working at different distances, each handing off to the next as the shark … Read more
A cat purring on your chest at 3 a.m. sounds like contentment. The same cat will purr on the vet’s table with a broken leg. One sound, opposite situations, and a mechanism that is stranger than a vibrating throat. Why do cats purr is a question with two separate answers: how the noise is made, … Read more
Cut into the roots of a Douglas fir and you find threads of fungus wrapped around them, extending outward into the soil for meters. Those threads connect neighboring trees. Carbon moves along them. Chemical signals move too. The question of how do trees communicate has a real answer, but it is narrower and messier than … Read more