What happens when entire mountain ranges disappear?
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00:00 Mountains.
00:05 They're born, they grow,
00:07 they age and erode.
00:09 And after a very, very long life,
00:12 they turn to dust.
00:13 What if all mountains collapsed at once?
00:17 What are the forces that might cause this to happen?
00:20 Could humans withstand the effects?
00:23 This is WHAT IF,
00:26 and here's what would happen
00:27 if the mountains collapsed.
00:29 We see mountains deteriorate all the time.
00:32 A 2015 earthquake that struck the Himalayas
00:35 triggered thousands of landslides at once,
00:37 wreaking havoc on the villages below.
00:40 Melting ice can also cause mountainsides to crumble
00:42 if the ice is integral to the mountains' structural stability.
00:46 Volcanoes are another big threat.
00:49 The 2018 Anak Krakatau disaster in Indonesia
00:53 saw the volcanic peak lose more than two-thirds of its height
00:56 and volume in a single week.
00:58 But how much worse does it get
01:00 when more than one mountain crumbles?
01:02 What would it take for all the world's mountains to collapse?
01:06 And what happens to you?
01:08 For years, scientists struggled to explain
01:11 why North America's version of the Andes Mountains
01:14 had disappeared.
01:15 Situated mostly over the Basin and Range Province
01:18 between the U.S. and Mexico,
01:20 this bygone mountain range
01:21 left evidence of its former glory behind,
01:23 without explaining why it went away.
01:26 A team of geophysicists at Melbourne's Monash University
01:29 came up with a theory for why it collapsed.
01:32 They studied the movement of tectonic plates,
01:35 more specifically subduction zones.
01:37 A subduction zone is created when two plates converge,
01:41 forcing one to slide underneath the other.
01:44 Subduction zones can form mountains,
01:46 but they can also bring them down.
01:48 When subduction zones decrease in size,
01:50 the velocity of the two plates is affected as well.
01:53 And that change creates a pull
01:55 that drives mountains to collapse.
01:58 Of course, this doesn't happen overnight.
02:00 The fall of the Basin and Range Mountains
02:01 played out over tens of millions of years.
02:04 If humans are playing the long game on Earth,
02:06 then the natural collapse of entire mountain ranges
02:09 is something we might have to contend with one day.
02:12 Let's fast forward to a world where
02:14 a combination of earthquakes,
02:15 melting ice,
02:16 volcanic activity,
02:18 erosion, and
02:19 whatever self-inflicted damage humans might cause
02:22 has either wiped out
02:23 or severely diminished Earth's supply of mountains.
02:27 While it would be a tremendous achievement
02:29 for civilization to last that long,
02:31 withstanding the brutal landslides,
02:33 eruptions,
02:34 and tsunamis that occurred along the way,
02:36 we might not be able to bask in it for very long.
02:39 That's because mountains play a pivotal role
02:41 in regulating carbon levels on Earth.
02:44 The fresh rock that emerged
02:46 during the periods of mountain formation
02:47 soaked up large amounts of carbon dioxide,
02:50 and helped the planet avoid sweltering,
02:52 inhospitable conditions.
02:54 But mountain rocks also emit carbon
02:57 through erosion and weathering.
02:59 And if mountain erosion
03:00 happens faster than mountain formation,
03:02 then the Earth's carbon dioxide levels
03:04 could become exponentially worse,
03:06 bringing us back to square one,
03:08 where Earth is once again inhospitable to human life.
03:12 So let's try not to peak too early.
03:14 Let's protect our mountains by doing everything we can
03:17 to prevent environmental degradation.
03:19 Mountains look out for us,
03:21 you look out for them.
03:22 And of course,
03:23 stay on the lookout for another WHAT IF.
03:26 [music]
03:32 (upbeat music)