00:00Phew, you can finally send that last report for the day and breathe out.
00:04The weekend is around the corner, but just when you're about to hit send, you're alarmed
00:09by the low rumbling under your desk.
00:11Is it the light rail passing by?
00:14Unfortunately, that's not the case.
00:16It's a volcano speaking!
00:18What, here?
00:20In Arizona?
00:21That's right, the ground keeps shifting under Arizona, reminding us that Earth is alive!
00:27No panic though, let's arm ourselves with some context.
00:3120 American states have extinct, active, and dormant, currently sleeping, volcanoes.
00:38Among such states, you can find California, New Mexico, Nevada, Utah, and Colorado.
00:50On the bright side, Arizona's volcanoes are dormant at the moment, but it doesn't mean
00:54they won't go off in the near, or not so near future.
00:59Now how about traveling to Arizona to check the traces of its active volcanic past?
01:05They dot the desert landscapes of this state like spots dot a dalmatian.
01:10There are entire volcanic fields southwest of Phoenix, east of Douglas, near Flagstaff,
01:20north of Kingman, and near the Mexico border.
01:24The most worrying thing about these fields is that even though they're not active at
01:29the moment, eruptions in this region might happen every thousand years or so.
01:34Well, the time seems to be up.
01:37The last powerful and destructive volcanic eruption occurred around 1,000 years ago at
01:42the Sunset Crater.
01:44Oh, this place is worth paying more attention to.
01:47And we will, but a bit later.
01:50First, we have to talk about hotspots.
01:52No, not that place where you can surf the web.
01:56In our volcanic context, a hotspot is a place where insane amounts of heat melt the overlying
02:02crust, Earth's thin outer layer, and form volcanoes.
02:06This heat rises from the mantle, which is located between our planet's dense, superheated
02:11core and the crust.
02:15Want to see an example of this type of volcanism?
02:18Welcome to the Hawaiian Islands.
02:21The Big Island has its active volcanoes because, at the moment, it's situated on top of the
02:26Hawaiian hotspot.
02:28The older Hawaiian Islands were once there too, but later they drifted off towards the
02:34northwest.
02:35It happened because that's where the oceanic crust on top of which they sat, namely the
02:40Pacific Plate, moved.
02:43Now look at the world's ocean basins.
02:45Yes, they're literally dotted with islands that sit on top of hotspots like Hawaii, Iceland,
02:53Samoa, the Galapagos.
02:56Those are probably the most famous examples.
02:59But don't think that continents can't host hotspots.
03:01They can, but those are far less common.
03:05One of the most famous continental hotspots is, ah, I bet you know it.
03:09Yep, the one beneath the Yellowstone Caldera.
03:13By the way, the caldera is a vast volcanic crater, especially one formed as a result
03:18of a massive eruption that led to the collapse of the mouth of a volcano.
03:24The Yellowstone Hotspot is basically the creator of Old Faithful and the rest of the hot springs
03:29and mud pots for which the national park is famous.
03:33Speaking of Old Faithful, let's make a small detour and pay more attention to this wonder
03:39of nature.
03:41It's one of the most well-known geysers in the world.
03:43People have been coming from all over the globe to see it for more than a century.
03:48The cool thing about this geyser is that the likes of it can only form under very specific
03:54conditions.
03:55That's why they're pretty rare.
03:58Magma under the surface superheats pockets of underground water.
04:02The pressure there keeps growing until it eventually pushes the water upward with immense
04:07strength.
04:09A certain volcanic rock with a high silica content lines the tunnel through which this
04:13water escapes.
04:15Basically, it creates a unique pipe that can withstand unbelievable pressure and heat created
04:21by the water erupting above the ground.
04:26Old Faithful was the very first named geyser in Yellowstone.
04:29If you come to visit it expecting the thing to erupt every hour on the hour, you're gonna
04:34be disappointed.
04:36On average, Old Faithful erupts every 91 minutes or so, which isn't that bad either.
04:41Plus, you can download a special app which will provide you with the approximate time
04:46of the next eruption.
04:48But be very careful while visiting and stay away from the site.
04:51The water erupting from the powerful geyser reaches 204 degrees Fahrenheit.
04:57The steam is even more scorching, up to 350 degrees Fahrenheit.
05:02It's hot enough to bake a cake.
05:06But let's get back to our volcanic hotspots.
05:09Scientists still don't clearly understand why there aren't many hotspot volcanoes on
05:14continental crust.
05:16One reason might be that the continental crust is much thicker than the oceanic crust, which
05:21is about four times as thick on average.
05:25Another reason could be that most of Earth's crust, about two-thirds of it, is oceanic.
05:31This means that there's less continental crust for hotspots to form under.
05:36Now, I bet those of you living in Arizona will appreciate the following info.
05:42We'll talk about a volcanic field right in the heart of this state, the San Francisco
05:47Volcanic Field.
05:50That's a massive area filled with over 600 volcanoes.
05:53Yes, they're mostly small, but it doesn't make them any less impressive.
05:58They're scattered across 1,800 square miles in northern Arizona, a giant territory.
06:04Interestingly, scientists are still debating about whether this volcanic field is actually
06:09sitting on top of a hotspot.
06:12But one thing they agree upon, the volcanoes in this area get younger as you move east.
06:17And this pattern matches up with the North American plate moving west over what could
06:22be a stationary hotspot beneath the surface of our planet.
06:26Cool, huh?
06:29The volcanic Holopaloo in that area started around 6 million years ago, so in geological
06:36terms, it's relatively young.
06:38As for the most recent eruption, it happened less than 1,000 years ago.
06:44The Sunset Crater, which I mentioned before, the one near Flagstaff, is the most famous
06:48vent from that eruption.
06:50The Sinagua people had to leave their homes at Wupatki Pueblo because of the eruption.
06:56That site is now part of the Wupatki National Monument.
06:59There, you can see how people lived in this volcanic region many years ago.
07:06If you go to explore this area, you'll notice that most of the volcanoes there are basalt
07:10cinder cones, small and steep.
07:13The Colorado Plateau has quite dry weather conditions.
07:17That's why the volcanoes haven't worn down much.
07:20Some of the best examples of those cones, like this one, called the SP Crater, still
07:25look like they appeared yesterday.
07:29But look around.
07:30It's not just cinder cones.
07:32The San Francisco Volcanic Field also has a stratovolcano, as well as some lava domes
07:38that formed from volcanic rocks with more silica than basalt you can find in places
07:43like Hawaii.
07:46It means they're thicker and don't flow as easily.
07:49Anyway, the stratovolcano is going to be one of the most epic sites you'll come across
07:54while exploring this volcanic field.
07:56Well not the stratovolcano itself, but the San Francisco Peaks, the remains of that giant
08:01formation.
08:03They stand tall at more than 12,600 feet.
08:07That's four and a half Burj Khalifas placed on top of one another.
08:11It makes the peaks some of the biggest landmarks in Northern Arizona.
08:16They're not only stunning, but also sacred to the Native American people who have lived
08:21in the area for many generations.
08:25Now unlike those super active volcanoes in Hawaii, the San Francisco Volcanic Field takes
08:31its time, thousands of years between eruptions.
08:35But you shouldn't relax just yet.
08:37Geologists say another eruption is likely to happen one day.
08:42It will probably occur in the remote eastern part of the field, away from big towns.
08:47Phew!
08:49If that next eruption is anything like the one that formed Sunset Crater, it would be
08:53quite the show.
08:55Lava fountains and rivers of lava flowing.
08:58At the same time, the next eruption might not happen for centuries, maybe even millennia.
09:05Until then, the San Francisco Volcanic Field will remain a hidden gem of volcanic history,
09:11waiting for its next fiery performance.
09:14That's it for today.
09:18So hey, if you pacified your curiosity, then give the video a like and share it with your
09:22friends.
09:23Or if you want more, just click on these videos and stay on the Bright Side!
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