[♪ INTRO]
Our planet is full of very weird places,
like toxic lakes and underground caves crawling with strange life.
And then there are some places that seem pretty ordinary,
they’re just…weirdly small.
Like, a miniature desert, or a teensy volcano.
But when you look a little closer,
there’s a lot more to these tiny geological misfits than meets the eye.
Our first stop is Canada’s Yukon Territory, right next to Alaska.
The Yukon is full of evergreen forests and rivers fed by melting snow and glaciers.
It’s mostly green, cold, and full of water.
But it also happens to be home to a dry, sandy patch of land called Carcross Desert.
The whole thing covers less than 3 square kilometers,
which is why it’s sometimes referred to as the smallest desert in the world.
Like, you could walk across it in less than 20 minutes.
And right on the other side, you’ll find more mountains, lakes, and evergreen trees,
just like the rest of southwestern Yukon.
But as random as Carcross Desert seems, it is no accident.
It’s the product of thousands of years of geological evolution.
During the last ice age, the whole region was covered by glaciers,
sometimes over a kilometer deep.
And as they retreated, the glaciers gouged the landscape
and filled valleys with meltwater, turning them into lakes.
Like, the spot where Carcross Desert is now used to be under 120 meters of water!
But over time, the water levels dropped and those lakes shrank.
Now, each spring, when the water level from nearby lakes is low,
wind from the mountains picks up exposed sand and dumps it on Carcross Desert,
constantly replenishing its supply.
But the catch about the so-called smallest desert in the world is…
that it’s not technically a desert.
Typically for something to be considered a desert,
it has to get less than 250 millimeters of rain a year.
Now, Carcross is a fairly dry place, because it sits in the
so-called rain shadow of nearby mountains.
Meaning that when clouds full of water roll in from the Pacific,
they run into the mountains and dump most of their rain before they get to Carcross.
But Carcross Desert still gets about 280 millimeters a year.
So scientifically, it is considered a dune system rather than a desert.
That might seem like a technicality, but the truth is,
Carcross Desert is really not that desert-like.
One main giveaway being that its plants and animals
don’t have much in common with true desert species.
But while these species make it clear that Carcross is not a desert,
they also tell us something else about Carcross.
See, they have a lot in common with another ecosystem, in Mongolia.
That’s because they evolved back before the
Bering Strait separated Asia and North America.
Back then, Yukon had a dry climate much closer to
the one in parts of Mongolia and Russia today.
And Carcross Desert ties this patch of the Yukon to its distant geological past.
So while it might not be the smallest desert, it’s still a very special place.
A few thousand kilometers down the West Coast, in northern California,
there’s a circle of peaks called the Sutter Buttes.
And they’re also sometimes called the world’s smallest mountain range.
To be fair—they are pretty puny.
They sit in a ring that's just 18 kilometers in diameter at its widest point.
And they’re only about 600 meters high.
In comparison, the mountain ranges on either side of them
run for hundreds of kilometers parallel to the coast,
and their peaks reach thousands of meters into the sky.
But while the Sutter Buttes are definitely small,
they are not actually a mountain range.
And they have a completely different history from the real mountain ranges around them.
For example, the Sierra Nevadas on the east and the Pacific Coast Ranges
to the west both formed when tectonic plates slid one over the other,
causing parts of the crust to crumple or rise into the air.
Meanwhile, the Sutter Buttes, which sit right between these two ranges,
are actually just… the remnants of an extinct volcano.
This volcano is sort of randomly located in a wide river valley
that actually used to be a sea for millions of years.
The valley is full of layers of sediment that washed in
from the surrounding mountains over time and eventually turned into rock.
And then, at some point, magma started to push up against the ground
at the location of the Sutter Buttes.
Some of this magma snaked up through the rock and oozed out the surface
to form steep features known as volcanic domes.
Then, a little over a million and a half years ago, the first domes started erupting.
There was round after round of these eruptions,
and some of them were so violent that they broke the rock off the domes.
Those broken pieces then slid down the domes and piled up in a ring around them.
And this happened over and over again
until there was a sort of apron of debris surrounding the core.
The raised valley floor between the volcanic core and
the apron has eroded away faster than the volcanic rock,
leaving behind a low-lying area that geologists call the moat.
But aside from a little erosion today, the Sutter Buttes don’t look all that different from
how they looked at the end of all those eruptions.
And these well preserved remains have made it possible
to piece together most of their origin story.
But one question that’s still not easy to answer is
why the Sutter Buttes formed where they did.
Like, why is there one lone volcano in the middle of the Sacramento River Valley?
And no one really knows, but geologists do have one idea.
An important clue is that studies have detected a narrow strip running
parallel to the coast that seems to have a stronger gravitational
and magnetic field than the surrounding areas.
And geologists think that it could be a sign of an old fault line that has been buried.
If that hypothesis is right, that fault could explain
how magma from deep underground rose up in that spot to form the Sutter Buttes.
The case is not closed yet, but what all of this does tell is that,
while the Sutter Buttes don’t have the honor of world’s smallest mountain range,
they are pretty exceptional in their own right.
In the outskirts of Puebla, Mexico, lies a rocky dome called Cuexcomate that has
sometimes been called the world’s smallest volcano.
Above ground, it stands about 8.4 meters tall,w
hich makes it about the same height as a three-story building.
At the top, it’s got a large crater that goes 4 meters below ground.
And people of the area have assumed it was a volcano for centuries.
The local government claims that it formed around 1000 years ago
and was active at least twice before going quiet.
But while scientific records don’t go back that far,
there is one thing that modern science can tell us about Cuexcomate:
It’s… not a wee little volcano.
It’s a giant geyser.
Now, geysers are often related to volcanic activity,
but they’re a completely different phenomenon.
They form in places where groundwater flows through rocks
that have been heated by magma.
As that water heats up, the amount of pressure it’s under increases,
and at a certain point, it’ll burst through
the surface of the Earth to release that pressure.
And voilà, you have a geyser.
These water-eruption sites are often located in the middle of cone-shaped structures.
That’s because the erupting water tends to be full of lots of dissolved minerals,
which get left behind when the water part evaporates.
But unlike volcanoes, they don’t spew lava, and they are much, much smaller.
In fact, part of the reason Cuexcomate has had its identity mistaken for so long is
the fact that it’s enormous for a geyser,
and may even be the largest geyser in the world.
But despite its size and the fact that we can’t directly prove what
came out of Cuexcomate when it was active, for volcanologists,
the shape and composition of the dome are a dead giveaway.
Its cone is made up almost entirely of calcite,
a type of deposit that isn’t super common among geysers,
but is definitely a mineral that commonly is deposited by groundwater.
And Cuexcomate still has warm water flowing through its base,
although now it discharges underground instead of through the crater.
As for why it formed where it did, that may be impossible to say for sure at this point.
Historical explanations have suggested that it formed during a period of activity
at Popocatépetl, a volcano about 60 kilometers to the west.
Scientists haven’t yet been able to prove or disprove this origin story.
But research at sites like Yellowstone have shown that volcanic activity can
push groundwater upward, through layers of rock,
where it can sometimes burst through the surface in a geyser.
So it’s possible that, though Cuexcomate is not a volcano itself,
iit did form because of volcanic activity.
No matter what, Cuexcomate still leaves the title of
world’s smallest volcano up for grabs…
and on the other side of the Pacific Ocean there’s another,
truly volcanic candidate in the running.
The volcano is named Taal, and it sits in the middle of
a lake on the island of Luzon in the Philippines.
It’s just over 300 meters high, and there in the middle of a peaceful lake,
it generally looks pretty tame and picturesque.
But this little volcano is very much active.
It’s erupted 30-some times in the last 500 years, including as recently as 2020.
Some eruptions have destroyed nearby towns,
and even reshaped the surrounding landscape.
Which might seem kind of drastic for such a wee volcano.
But… there’s a reason it blows up so dramatically.
That lake it’s sitting in?
It’s actually a caldera belonging to a much larger volcanic system.
Taal technically encompasses this whole enormous volcano,
but all its recent activity has been out of this visible part,
known as Volcano Island, which is why people tend to think it’s small.
The caldera it’s sitting in hasn’t exploded in at least 5000 years.
But there’s still a lot going on beneath the surface.
And that has to do with the type of volcano Taal is.
See, when you imagine a generic volcano,
you’re likely picturing a cinder cone volcano.
These are pretty simple explosions.
Basically, lava bursts out of the earth through a single vent, hardens,
and then falls around the vent, forming a tidy cone with a crater.
But Taal is what’s called a stratovolcano, and it’s a completely different beast.
Stratovolcanoes have what’s called a conduit system,
basically a system of channels leading magma up
from deep below the surface of the Earth.
The volcanoes grow over time as different explosions dump
alternating layers of lava, ash, or other debris one on top of the other.
And what makes these so dangerous and unpredictable is that
they don’t always blow out the top.
As magma pushes through different branches in the conduit system,
it can burst out the side.
Like, in 1707, Taal exploded out of a different part of the caldera and
formed a brand-new cone that’s now part of Volcano Island.
And Volcano Island also has at least five other vents
where the volcano has erupted in the past.
So while Taal looks deceivingly small, the part we see is just the tip of the iceberg.
And this volcano has had a massive impact on the land around it for centuries.
If there’s one thing that all of these geological misfits have in common,
it’s that none of them are quite what they seem.
And first impressions alone often don’t tell us the full geological story of a place.
All over our planet, completely ordinary geological processes
are making some amazingly weird places.
And studying the oddballs and the extremes can help scientists
sharpen their understanding of the more ordinary ways
the ground is slowly evolving under our feet.
Thanks for watching this episode of SciShow!
If you enjoyed learning about these small, weird places,
we bet you’ll love some of the much bigger ones we’ve talked about!
Like, we have this one about 5 super weird lakes
which you might want to check out next.
And, hey, pro top: if you subscribe to the channel,
you’ll get videos like that popping up in your YouTube feed all the time!
So, something to consider.
[♪ OUTRO]