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Why Iceland's lava is so hard to control - Arianna Soldati - Video học tiếng Anh
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Why Iceland's lava is so hard to control - Arianna Soldati
Why Iceland's lava is so hard to control - Arianna Soldati
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Phụ đề (75)
0:06
Late at night on December 18th, 2023,
0:10
the Icelandic citizens of Grindavik experienced their worst nightmare.
0:15
After weeks of earthquake-filled suspense,
0:18
a volcanic fissure opened four kilometers northeast of town
0:22
and began spewing lava fountains 100 meters tall.
0:26
Luckily, the molten rock flowed elsewhere, narrowly avoiding the small fishing town.
0:32
But Iceland wasn’t willing to leave Grindavik’s fate to chance again.
0:37
To prepare for future eruptions,
0:39
the government began exploring how to control
0:41
these red-hot rivers of destruction.
0:45
Steering a lava flow is about as difficult as it sounds.
0:49
Molten rock, which we call magma when it's underground,
0:52
and lava when it breaks through the Earth's surface,
0:55
can reach temperatures of roughly 1,200° Celsius.
1:01
That's over four times hotter than the maximum temperature
1:04
of a standard kitchen oven—
1:06
now imagine that heat radiating from several square kilometers.
1:11
At this temperature, lava ignites or melts most things in its path.
1:17
And since it's as heavy and dense as the rocks it's composed of,
1:20
its flow is almost unstoppable.
1:23
Fortunately, there are two factors that make lava flows a little easier to handle.
1:28
First, while it can take decades to cool completely,
1:32
lava becomes solid and still after cooling to roughly 600° Celsius.
1:38
This process typically happens on its own in just a few hours,
1:42
unless an ongoing eruption is fueling the flow.
1:45
Second, lava generally flows at a rate of less than 1 kilometer per hour.
1:51
This slow speed gives people time to evacuate
1:54
and respond with various solutions—
1:56
though some ideas are better than others.
1:59
One questionable strategy
2:01
championed by the first Director of the Hawaii Volcano Observatory,
2:06
Thomas Jaggar,
2:07
was to fight lava with bombs.
2:11
When the 1935 eruption of Mauna Loa threatened the Hawaiian town of Hilo,
2:16
he convinced the US Army Air Corps to drop 20 bombs on the flowing lava
2:21
to disrupt its path and stop its advance.
2:25
Six days after the operation, the lava did stop flowing,
2:28
prompting Jaggar and the US Air Force to label their mission a success.
2:33
But today, most volcanologists consider the timing to be a coincidence.
2:38
Since lava flows like a liquid,
2:40
experts believe the bombs merely displaced it temporarily,
2:44
forming a crater which flowing lava then refilled.
2:48
Perhaps the more obvious solution is to cool lava with water.
2:52
Due to lava’s low heat conductivity this requires an enormous amount of H2O,
2:58
but that didn’t stop the Icelandic government in 1973.
3:02
When the Eldfell volcano erupted
3:04
and lava began streaming towards the Heimaey Harbor,
3:08
they began a highly coordinated effort
3:10
to pump 6 million cubic meters of seawater onto the lava flow.
3:15
That’s enough to fill 2,400 Olympic-sized swimming pools.
3:20
At the peak of their efforts to manage this 6-month long eruption,
3:24
75 people worked in shifts around the clock,
3:27
spraying down each actively advancing area for roughly a full day to stop its flow.
3:33
This approach did save the harbor,
3:35
but it could only work in a place with access to this much water.
3:39
Regions further from the coast require different defenses,
3:42
like large earthen barriers.
3:45
Typically made of materials like sand, dirt, or volcanic gravel,
3:49
these barriers can divert lava flows away from populated areas.
3:54
For example, when Italy’s Mount Etna erupted in 1983,
3:58
workers used 750,000 cubic meters of material—
4:03
the equivalent of 25,000 truckloads— to erect four large barriers.
4:09
The people of Grindavik took a similar approach after the 2023 eruption,
4:13
building 25-meter-high barriers that successfully diverted lava
4:18
from multiple eruptions.
4:20
Since the diverted lava raises the ground level as it flows,
4:24
these barriers had to be raised between each eruption.
4:27
But the advantage of this approach is that it allows regions
4:30
to build up defenses between flows instead of during them.
4:35
Scientists are still working to better predict
4:37
exactly where lava flows will emerge, what direction they’ll travel,
4:42
and just how much lava an eruption will produce.
4:45
But once they figure it out,
4:47
engineers can leverage existing strategies
4:49
to protect communities from these otherwise awe-inspiring eruptions.
