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What China's Stone Forest Teaches Us About Cities - Video học tiếng Anh
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What China's Stone Forest Teaches Us About Cities
What China's Stone Forest Teaches Us About Cities
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0:00
In the Yunnan Province of southern China,
0:02
there’s a forest made of stone!
0:04
Well, kind of. The famous “Stone Forest” is actually a natural collection
0:09
of unusual rock formations, including pillars up to 30 meters tall!
0:15
Its unique landscape has made the Stone Forest
0:17
a popular attraction for tourists and scientists alike.
0:20
Millions of people have made the trip to stare up at these rock pillars
0:24
and wonder how the heck they ended up in such weird shapes.
0:28
And for good reason! Stone Forest’s rock formations
0:32
have a lot to teach us about the geological past,
0:35
and may even help us design better cities in the future.
0:41
[♪INTRO]
0:43
If you want to visit the Stone Forest yourself,
0:45
all you have to do is travel about 80 kilometers southeast of Kunming,
0:49
the capital city of China’s Yunnan Province.
0:52
There, you’ll find a massive maze of stone arches,
0:56
pillars, tunnels, caverns, mushroom-like towers, and more.
0:59
The geological smorgasbord covers an
1:01
area of more than 350 square kilometers.
1:05
These formations are such a world wonder that the Stone Forest–
1:09
locally known as Shilin World Geopark–
1:12
was named a UNESCO World Heritage Site in 2007.
1:15
If you think a forest made of stone is cool,
1:18
wait until I tell you it’s not the only one!
1:21
Similar stone forests are found in several other Chinese provinces,
1:24
as well as other countries like
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Malaysia, Indonesia, Australia, and Brazil.
1:29
They all formed the same way,
1:31
through a geological process known as karstification.
1:35
The stone of Yunnan’s Stone Forest
1:37
is more than 260 million years old–
1:41
that’s older than the first dinosaurs!
1:43
And at that time, Yunnan Province was
1:45
covered by the Paleo-Tethys Sea.
1:47
The rock layers consist of carbonate rocks like limestone
1:50
and dolostone, which are formed from
1:52
the remains of shallow ocean organisms.
1:55
Lots of sea creatures – especially tiny shelled plankton –
1:59
build shells out of calcium carbonate.
2:01
When they die, their bodies sink to the seafloor and add those
2:04
minerals to layers of mud, which eventually solidify into stone.
2:09
Fast forward a few million years, and tectonic
2:11
activity forced these rock layers upward,
2:14
exposing that ancient sedimentary stone
2:16
to weathering forces like wind and water.
2:19
And that’s when the really exciting stuff happens.
2:22
See, the thing about carbonate rocks is that
2:24
they are easily dissolved by rain and streams.
2:27
As water flows over the stone, it corrodes
2:29
the rock and carries away little bits of it.
2:32
Over long time periods, those little sections of dissolving
2:35
rock develop into crevices, caverns, and a complex
2:39
assortment of shapes known as a karst landscape.
2:43
Karst landscapes are known all over the world.
2:46
They happen anywhere there’s lots
2:47
of limestone exposed to the surface.
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They can feature deep caves,
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dangerous sinkholes, stone towers, and more.
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But no place on Earth has a karst
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landscape as complex as Shilin Stone Forest.
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This one area includes nearly every known type of karst formation.
3:03
It’s like the Disney World of karst.
3:05
The shape of each specific rock formation is a record of all
3:08
its exposure to water and its natural points of weakness.
3:12
Over those many millions of years, as tectonic forces acted upon these
3:16
rocks, they developed cracks and fissures, which then became the
3:20
areas where water tended to collect and gouge through the stone.
3:24
Clusters of stone pillars used to be solid hills.
3:27
But as water carved down and down along natural crevices,
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it split the hill into towering segments.
3:33
In some cases, the rock had more cracks in its lower layers,
3:37
which caused the base to dissolve away more quickly,
3:39
leaving narrow pillars with bulbous, mushroom-like tops.
3:43
A close look at the local rock formations reveals tinier details,
3:47
like little channels and grooves etched by rainwater.
3:50
And to this day, the shape of the Stone Forest continues to change.
3:54
Some researchers estimate that the pillars are growing!
3:57
This is because the erosion of the soil at ground
4:00
level is faster than the erosion of the stones themselves.
4:03
So the ground level and the top of the
4:05
pillars are growing farther and farther apart.
4:08
Thanks to a wet and humid climate,
4:10
and a vast array of slightly damaged carbonate rocks,
4:14
Stone Forest is one of the best places in the world for
4:17
scientists to study the interaction between stone and water.
4:20
Those scientists need funding, and we do, too.
4:24
So here’s a short ad.
4:26
Since you watch SciShow,
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4:31
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4:34
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5:16
Besides just looking cool, there are even fossils within the stone pillars!
5:21
These include the shells of molluscs, gastropods,
5:24
and lots of tiny plankton and algae from
5:26
the ancient ocean that once covered this region.
5:29
And this karstification process has been
5:31
going on for hundreds of millions of years!
5:33
At Stone Forest, the beautiful rock
5:35
formations are exposed at the surface.
5:38
But at some nearby locations, rocks of the same age are buried
5:41
beneath ash and lava rocks from ancient volcanic eruptions.
5:45
When geologists examined these volcanic deposits,
5:49
they found the shape of caverns, sinkholes,
5:51
and giant stone pillars underneath the lava rocks!
5:55
These were ancient stone forests that became completely
5:58
buried by volcanic eruptions, more than 250 million years ago!
6:04
But there’s more to these giant rocky pillars
6:06
than lessons about the distant past.
6:09
These stone formations might hold some
6:11
clues to building better cities in the future.
6:14
That’s because Stone Forest has its own climate.
6:17
See, all that exposed rock absorbs lots of heat from the sun,
6:21
just like a concrete wall on a hot day.
6:24
But those tall pillars also create pockets of cool shade.
6:28
Research has found that, compared to the surrounding landscape,
6:31
Stone Forest experiences a higher average daily temperature,
6:34
but less dramatic temperature fluctuation,
6:37
and highest daily temperature peaks occur later in the day.
6:41
I bet you’ve already figured out an analogous
6:43
landscape full of tall stony pillars: cities full of skyscrapers.
6:48
Those peculiar climate patterns of Stone Forest
6:51
are surprisingly similar to what has been observed in cities.
6:54
But cities also have a lot of other climate-altering effects going on,
6:58
like air pollution and car exhaust, which makes it tough for
7:01
scientists to figure out how much of the temperature
7:04
changes can be attributed just to the shapes of the buildings.
7:07
But Stone Forest has skyscraper-like shapes
7:10
without any of those other confounding factors!
7:13
So researchers are hopeful that studying this natural
7:16
landscape might help us better understand the ways that
7:19
cities shape local temperatures, and maybe even guide
7:22
us in building more ecologically-friendly cities in the future!
7:26
This incredible landscape is also in danger, though.
7:30
Human activity in the area has disturbed the ecosystem
7:33
of plants and animals living around the rock formations.
7:36
Karst ecosystems are especially sensitive to external disturbances.
7:41
Some research has found that Stone Forest has been experiencing
7:44
an expansion of barren areas and a decrease in forested areas.
7:49
Like the actual, living forest /within/ the Stone Forest park.
7:53
So in addition to studying the landscape,
7:55
scientists are working on conservation plans to preserve it,
7:59
to keep this extraordinary natural
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wonder rock solid for as long as we can.
8:05
[♪OUTRO]
