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.