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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, which 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].