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[♪ INTRO]
In New Mexico’s Tularosa Basin, there is a desert filled with blindingly white sand.
The aptly named White Sands National Park has over 400 square kilometers
of incredibly pure gypsum sand.
It’s the largest area of its kind in the world,
and its formation and survival defy the odds.
How this much pure gypsum ended up in one place is an incredible story
of geologic puzzle pieces falling precisely into the right places at the right times.
And once they all did, the white sands led to an incredible set of unique creatures
many of which are also eerily white.
250 million years ago, the area that now holds the white sands
was part of the ancient supercontinent Pangea, and covered by the Permian Sea.
The sea was a shallow basin that was originally connected to the larger ocean,
with a coastline that stretched across what is now
Texas, Arizona, and New Mexico.
The layers of gypsum formed gradually, as sea levels went up and down.
See, when the levels went down,
the water ended up trapped on land in massive salt lakes.
Gypsum is a mineral made of calcium sulfate.
As these lakes evaporated, the calcium and sulfate in the water were left behind,
forming a layer of gypsum.
Eventually, these layers built up to be nearly 500 meters thick.
Then, around 70 million years ago,
tectonic forces compressed North America
and pushed the gypsum layer up into the mountains.
And then roughly 30 million years ago,
the same forces pulled apart in the opposite direction,
ripping open a massive valley, surrounded by the gypsum layer in the mountains.
That valley surrounded by these gypsum mountains
is what we call the Tularosa Basin today.
24 thousand years ago, the last glacial period brought rains
that dissolved the gypsum in the mountains and carried it down to the valley.
But just like what happened with the Permian Sea
hundreds of millions of years before, when things dried up,
the water evaporated and left the gypsum behind.
Over the past 10 thousand years,
winds have slowly broken that apart, making sand that’s over 98% pure gypsum.
It’s especially remarkable because gypsum is rare to find in any sand.
It dissolves in water, so rain or waves just wash it away.
The only reason the white sands have survived this long is because they’re so dry.
So today, we see the culmination
of a remarkable 250 million year process of sorting, transporting,
and purifying gypsum to make a truly one-of-a-kind place.
While none of these processes are totally unique on their own,
there is nowhere else on Earth where they have come together at this scale.
There are big gypsum-rich areas of Mars, though,
which actually makes the white sands a great place for geologists
to learn more about the features of the Red Planet.
Meanwhile, here on Earth, unique places often mean unique life,
and the white sands are no exception.
But it’s not an easy home to have.
There isn’t much water or many nutrients around.
Plants need deep roots to reach water and avoid being blown away.
They also need to grow tall, and quickly, to avoid being buried by the dunes.
Despite these challenges, plants like the soaptree yucca
and the Rio Grande cottonwood can survive life in the white sands.
Too much calcium is toxic, so some of these plants have developed special ways
of dealing with the huge amount they get from the gypsum.
Some can excrete their extra calcium through salt glands,
basically a special type of plant sweat.
Others crystallize the extra in their leaves.
That turns the calcium into a form that’s
harder to dissolve or absorb by the plant’s cells,
essentially storing it away in a vault to protect the rest of the plant.
Life on the sands can be rough for animals as well.
They need to survive without much water,
and with a blank white background, it can be easy for predators to spot them.
45 species are endemic to the white sands, meaning they are only found there.
Many of these, like the camel cricket, pocket mouse, bleached earless lizard,
and a whole bunch of moths are ghostly white.
As you might have guessed, this is camouflage against the white landscape.
Because colorful animals are so easy to spot,
the forces of natural selection are very strong.
For example, two different lizard species have mutations
in a gene that receives signals to make darker pigments, turning the lizards white.
That mutation was selected for so strongly that it spread through
the entire population in less than 10 thousand years,
that’s lightning-fast in evolutionary terms.
Similar adaptations have evolved independently in multiple species,
an example of what biologists call convergent evolution.
These processes help create the endemic species.
Once a creature is blindingly white,
it’s hard to go back to living anywhere but the gypsum sands.
It’s just another example of all kinds of geologic forces coming together
to create a truly unique environment, and evolution stepping in to create
one-of-a-kind life adapted to living only there.
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