There are many kinds of floods.

River floods develop slowly, water gradually rising over days, providing ample time to evacuate.

Coastal floods come mostly from storm surges, when a hurricane or tsunami makes landfall.

Coastal communities also have evacuation warnings. But when not, these can be catastrophic.

Urban flooding happens increasingly as paved areas expand, preventing the land from absorbing rainfall.

Flash floods, though often localized, can be the deadliest for their size, simply because they are sudden.

They occur when torrential rain falls, snow rapidly melts, or water is forced down a river.

They can send a wall of water tens of feet high hurtling down a channel, faster than people can seek safety.

They can sweep away vehicles and roads, making escape impossible.

They can carry debris and chemicals, leaving long-lasting devastation in their path.

Despite a few fatal incidents, authorities are improving their ability to predict and react.

AI analysis of massive weather data now provides longer lead times for flash floods, especially in the Southwest U.S., Latin America, and Asia.

Meanwhile, smarter urban planning and development include runoff zones to capture floodwaters, and innovative warning systems that alert and prepare the populace.

In the rare case you receive an alert, move quickly to high ground and stay safe.

In 2024, Spanish oceanographers studying the deep seafloor west of the Canary Islands discovered an enormous seamount --

A mile-high, 70-mile long mountain on the bottom of the ocean, formed of three inter-linked ancient volcanoes.

At its summit, just 200 feet beneath the water’s surface, they found sand dunes and cliff faces that could only have been formed if it had once been above water.

During the last Ice Age, when Earth’s water was locked up in continental ice sheets, sea level was over 300 feet lower.

Meaning that at least 100 feet of the seamount would have risen above the water, to form an island many miles long

It was almost directly west of the Straits of Gibraltar – exactly where Plato had described the city of Atlantis, before it sank beneath the waves.

Could it be? These scientists began to wonder, had they accidentally discovered the lost city?

They sent down the ship’s ROVs – Remote Operated Vehicles, to explore the surface of the seamount.

They found sediments and other evidence of erosion, only possible if the island were indeed above water.

But unfortunately, no ruins of an ancient city, or any evidence of human habitation.

Their continued research did provide valuable data about the volcanic past of the eastern Atlantic, the geologic formation of seamounts, and how they impact ocean currents – their original mission.

But Atlantis remains elusive, perhaps waiting for future scientists.

Just eight percent of Earth’s surface is covered in topsoil -- but that grows 95 percent of our crops.

And healthy plant growth depends on healthy soil. Which depends on a healthy population of soil life.

As noted in an earlier EarthDate, a single handful of healthy soil contains more microbes than the human population of Earth.

And more biodiversity than the entire Amazon. One handful.

Along with microbes, there are fungi, worms, insects, plant roots, and much more. And they all make noise.

Sixty years ago, ecologists began recording the sounds of nature, to understand what species populate different areas – cataloging, for example, the bird, insect, and animal noises of a forest.

But when one curious scientist poked a microphone into the ground, he was blown away.

Turns out soil life makes noises of its own. From grubs chewing on roots, to worms slithering through tunnels, to millipedes’ feet drumming.

In fact, they realized you can tell a lot about soil health simply by listening to it.

Conversely, degraded soils have less active life, and therefore less sound.

Ecologists now monitor soils with a microphone, helping evaluate their resident lifeforms, crop productivity, and the success of soil replenishment programs.

Their discoveries remind us that soil is a vital, living system, worth protecting for its own sake – and ours.

Sand dunes are dynamic, always changing.

They occur wherever there’s sand, even thousands of miles from the sea. Even on the shores of freshwater lakes.

And the largest freshwater dunes in the world, more than 400 feet high, are in Michigan, on the shores of the Great Lakes.

They’re made of sand formed during the last Ice Age.

Continental glaciers ground up rock as they moved, and deposited sand in the basins that would become the Great Lakes.

Dunes form here, like everywhere, when wind picks up sand and carries it across the land -- until it meets an obstacle, like a rock or shrub.

That slows the wind and causes it to drop its sand, which piles up around the object.

The sand pile grows and becomes its own sand-catcher. More sand is deposited and, over centuries, a dune rises.

The Great Lakes sand dunes have been there at least that long. Though within the last few decades they’ve come under threat.

Sand mining carts them away in truckloads. New buildings block wind that could replenish them. Off-road vehicle traffic cuts some dunes nearly in half.

But state leaders, conservation groups, and volunteers have teamed up to save the dunes.

They’ve declared large areas protected. Limited mining and development. Reestablished native dune plants. Built boardwalks and trails to reduce erosion.

Together, they may be able to preserve the Great Lakes dunes for centuries, and visitors, to come.

Each year, U.S. drivers collide with 1 to 2 million large animals, often killing them and endangering the drivers.

Add in smaller creatures, and studies estimate up to 300 million animals die on U.S. roads annually. An astounding number.

This is because wildlife must roam, and always has -- to find food and water, breed and raise young, and migrate seasonally.

They often follow ecological corridors dictated by geography and natural resources.

These pathways could be millennia old. But in the last century, they’ve been dissected by roads and highways.

The result is that either animal populations become isolated in small areas, where they can starve, become prone to disease or inbreeding.

Or they cross roads and court danger.

This has led communities around the world to build thousands of wildlife crossings – bridges or tunnels that guide animals safely across roads, railways, and open development.

They’re usually constructed along existing animal corridors.

While often made of concrete, they’re covered in soil, plants, and rocks to simulate natural habitat.

They can be hundreds of feet long and cost millions of dollars. But their results are astonishing.

They’ve reduced animal mortality in problem areas by more than 90%, and saved drivers from thousands of accidents.

As human development continues to expand, wildlife crossings stitch ecological pathways back together.

Billions of years ago, the globe spun twice as fast as today; a complete rotation took just 6 hours.

Then Earth’s rotation slowed, and that’s why you’re here listening to this episode. Let me explain.

The atmosphere of early Earth was made up of methane, CO2 and sulfur gases. But no oxygen.

Eventually, as noted on a prior EarthDate, cyanobacteria, blue-green algae, began to produce oxygen through photosynthesis.

At first, the amount of oxygen they released was so small that it was absorbed by iron in seawater, and no oxygen entered the atmosphere.

Scientists researching this phenomenon found a similar low-oxygen, high-sulfur environment in sinkholes at the bottom of Lake Michigan, where modern blue-green algae grows.

There, and in a lab mimicking that environment, they tested the effects of day duration on oxygen production.

Turns out blue-green algae is dormant in the morning. In a short day, it was nearly dark again by the time it started producing oxygen.

And that small amount was reabsorbed by the algae before it could enter the water.

As days lengthened, the algae had enough time to produce enough oxygen to escape.

Over millions of years, oxygenated water first gave rise to aerobic sea life.

Then an oxygen-rich atmosphere allowed land creatures to develop and thrive, which eventually led to…

you, and me, and a radio show called EarthDate.

Greenhouse gases trap heat in the atmosphere and keep Earth warm. Without them it would be a frozen iceball – as it once was before.

There are many greenhouse gases. Water vapor is by far the largest by volume, and does most of the warming.

Carbon dioxide is the weakest greenhouse gas in warming potential, but the second most abundant.

Carbon is always moving between Earth and sky in what’s called the carbon cycle.

But since humans have industrialized, we’re transferring carbon that was held in fossil fuels into the atmosphere, where it lasts about a century.

We measure the warming impact of other gases in CO2 equivalent.

Methane, for instance, is 80 times more potent than CO2, but lasts in the atmosphere only a few decades.

It’s naturally produced by decaying plants in swamps, lakebeds, and forest floors. And by human sources like natural gas leaks and livestock.

Nitrous oxides also occur naturally, emitted from soils beneath wild plants and oceans. And through our agriculture, by using nitrogen-based fertilizers.

These are 300 times more potent than CO2, though produced in much smaller quantities.

Fluorinated gases are manmade, and emitted only from human sources, like leaking refrigerant.

The volume is tiny, but they’re thousands of times more potent than CO2, and endure for thousands of years.

Only by understanding the mix and potency of greenhouse gases can we understand how to best manage them.

Five centuries ago, the last emperor of the Aztecs drank a full gallon each day of a coveted beverage, rich in vitamins and caffeine.

The Aztec word for it: xocolatl Chocolate.

Just like today’s chocolate drinks, his was made from the ground seeds of the cacao fruit.

The Olmecs and Mayans before him domesticated the cacao, an understory tree from Ecuador.

There and in Mexico, it thrived – under very specific conditions:

Steady warm temperatures. Abundant rainfall. Well drained volcanic soil, high in minerals.

When the cacao tree blooms, its flowers must be pollinated within 48 hours, by ants or small flies. As few as 20% of pollinated flowers produce fruit.

And those fruits hold only a handful of seeds, which must be fermented to mellow their bitter taste before they’re fit for consumption.

Mexican civilizations mixed their cacao with water, chilis, and spices. European invaders added sugar and milk to make chocolate bars.

They took the cacao to their island colonies and to Africa, where growing conditions mimicked Mesoamerica.

Today, rising heat, changing rainfall, deforestation, and overproduction jeopardize the global cacao trade.

But choco-holics don’t despair. Scientists are working with cacao farmers to develop new hybrids and sustainable farming practices to keep this sweet treat with us for centuries to come.