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In the 13th Century, Genghis Khan embarked on a mission to take over Eurasia, swiftly conquering countries and drawing them into his expanding Mongol Empire.
With his vast armies he became almost unstoppable.
But, legend has it that there was one obstacle that even the impressive Khan couldn't overcome.
A towering wall of ice, grown by locals across a mountain pass to stop the Khan's armies from invading their territory.
No one knows how historically accurate that particular story is, but remarkably, it draws on fact.
For centuries, in the Karakoram and Himalayan mountain ranges, people have been growing glaciers and using these homemade bodies of ice as sources of drinking water and irrigation for their crops.
But before we get to that fascinating phenomenon, it's important to understand the difference between glaciers that grow in the wild, and those that humans create.
In the wild, glaciers require three conditions to grow.
Snowfall, cold temperatures, and time.
First, a great deal of snow falls and accumulates.
Cold temperatures then ensure that the stacked up snow persists throughout the winter, spring, summer, and fall.
Over the following years, decades, and centuries, the pressure of the accumulated snow transforms layers into highly compacted glacial ice.
Artificially growing a glacier, however, is completely different.
At the confluence of three great mountain ranges, the Himalayas, Karakoram, and Hindu Kush, some local cultures have believed for centuries that glaciers are alive.
And what's more, that certain glaciers can have different genders, including male and female.
Local Glacier Growers "breed" new glaciers by grafting together—or marrying—fragments of ice from male and female glaciers.
Then covering them with charcoal, wheat husks, cloths, or willow branches so they can reproduce.
Under their protective coverings, these glacierets transform into fully active glaciers that grow each year with additional snowfall.
Those then serve as lasting reserves of water that farmers can use to irrigate their crops.
These practices have spread to other cultures, where people are creating their own versions of glaciers and applying them to solve serious modern challenges around water supplies.
Take Ladakh, a high-altitude desert region in northern India.
It sits in the rain shadow of the Himalayas and receives on average fewer than ten centimeters of rain per year.
As local glaciers shrink because of climate change, regional water scarcity is increasing.
And so, local people have started growing their own glaciers as insurance against this uncertainty.
These glaciers come in two types: horizontal, and vertical.
Horizontal glaciers are formed when farmers redirect glacier meltwater into channels and pipes.
Then carefully siphon it off into a series of basins made from stones and earth.
Villagers minutely control the release of water into these reservoirs, waiting for each new layer to freeze before filling the basin with another wave.
In early spring, these frozen pools begin to melt, supplying villagers with irrigation for their fields.
Local people make vertical glaciers using the meltwater from already-existing glaciers high above their villages.
The meltwater enters channels that run downhill, flowing until it reaches a crop site where it bursts forth from a pipe pointing straight into the air.
When winter temperatures dip, this water freezes as it arcs out of the pipe, ultimately forming a 50 meter ice sculpture called a stupa, shaped like an upside-down ice cream cone.
This inverted form minimizes the amount of surface area it exposes to the sun in the spring and summer.
That ensures that the mini-glacier melts slowly and provides a reliable supply of water to feed the farmers' crops.
These methods may be ancient, but they're becoming more relevant as climate change takes its toll on our planet.
In fact, people are now growing their own glaciers in many regions beyond Ladakh.
Swiss people, utilizing modern glacier growing technology, created their first stupa in 2016 in the Swiss Alps.
There are plans for over 100 more in villages in Pakistan, Kazakhstan, and Kyrgyzstan.
Perhaps one day we'll be able to harness our homegrown glaciers well enough to build whole walls of ice.
This time not for keeping people out, but to enable life in some of the planet's harshest landscapes.
As Nikola Tesla said, the progressive development of man is vitally dependent on invention.
Check out this playlist to see some of the ingenious inventions, giving us hope for a brighter future.
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【TED-ED】自分たちで氷河を作る方法―M・ジャクソン How to grow a glacier - M Jackson

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Vvn Chen 2019 年 7 月 24 日 に公開
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