# What big cities are most at risk from volcanoes? **URL:** \ **Category:** Factual Questions\ **Created:** [May 9, 2007, 8:48pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446 "2007-05-09T20:48:14Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Captain\_Lance\_Murdoch](https://avatars.discourse-cdn.com/v4/letter/c/47e85d/32.png) [@Captain\_Lance\_Murdoch](https://boards.straightdope.com/u/Captain_Lance_Murdoch)\ **Post date:** [May 9, 2007, 8:48pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/1 "2007-05-09T20:48:14Z")
I’m thinking Tokyo, Japan, Naples, Italy and Seattle, USA are near the top of the list. What other major population centers are near volcanoes that are bound to blow their tops sooner or later? ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [May 9, 2007, 9:17pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/2 "2007-05-09T21:17:57Z")
[Los Angeles](http://www.imdb.com/title/tt0120461/) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 9, 2007, 9:53pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/3 "2007-05-09T21:53:48Z")
Of course, looking at it a different way, everything in the Northern Hemisphere is at risk from Yellowstone. It doesn’t blow often, but when it does, it’s a big’un, and it’s overdue. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [May 9, 2007, 10:00pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/4 "2007-05-09T22:00:24Z")
Mexico City - Popocatepetl is close. ---
**Author:** ![A.R.Cane](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@A.R.Cane](https://boards.straightdope.com/u/A.R.Cane)\ **Post date:** [May 9, 2007, 10:21pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/5 "2007-05-09T22:21:52Z")
Mt. Hood lies immediately south of the Columbia river, if an eruption were to block the river, a likely scenario, the resulting flood would be catastrophic for a large metropolitan area. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [May 9, 2007, 10:25pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/6 "2007-05-09T22:25:36Z")
The question about Rainier got raised a while ago. Short answer: it depends on the type of eruption and the volume/severity of it, and also which way any lava flow emerges. But most likely the Kent Valley is toast, Tacoma is only slightly less likely to get severe damage. Seattle will _probably_ not be at risk from lava flow, but could conceivably be in the path of a pyroclastic cloud or other ash/gas fallout from the eruption. Mount Hood is some distance from Portland, but upstream. Danger is debatable depending on a lot of factors. Mt. Tanzawa is about 20 miles due east of the Kawasaki-Yokohama industrial-port complex, and less than 30 from Tokyo. Whether it’s active enough to be a danger is something I don’t know. Likewise two volcanoes directly adjacent to Kyoto and within fairly close proximity to Osaka. Vesuvius is less than ten miles from downtown Naples, southwest along the coast, and of course directly above some coastal outliers in the metropolitan area. Etna could theoretically be a severe threat to Catania, Sicily, though its normal eruption is not the catastrophic style that would endanger a city. ---
**Author:** ![Lanzy](https://avatars.discourse-cdn.com/v4/letter/l/74df32/32.png) [@Lanzy](https://boards.straightdope.com/u/Lanzy)\ **Post date:** [May 9, 2007, 10:29pm UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/7 "2007-05-09T22:29:57Z")
I think the most active volcano is in Hawaii. Not the big exploding type but the oozing lava type. Don’t know if cities are involved but 80 houses have been destroyed since 1982. Also don’t know why this can’t increase to threaten more area. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [May 10, 2007, 12:38am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/8 "2007-05-10T00:38:13Z")
[QUOTE=Lanzy] I think the most active volcano is in Hawaii. Not the big exploding type but the oozing lava type. Don’t know if cities are involved but 80 houses have been destroyed since 1982. Also don’t know why this can’t increase to threaten more area. [/QUOTE] There’s nothing around there large enough to be called a “big city.” The closest would be Hilo, which isn’t in the lava’s path. It’s more likely to be destroyed by a tsunami than by a volcano. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [May 10, 2007, 12:39am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/9 "2007-05-10T00:39:23Z")
[QUOTE=Chronos] Of course, looking at it a different way, everything in the Northern Hemisphere is at risk from Yellowstone. It doesn’t blow often, but when it does, it’s a big’un, and it’s overdue. [/QUOTE] Actually, the entire planet is at risk from that one. Any day now. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 10, 2007, 12:46am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/10 "2007-05-10T00:46:37Z")
[QUOTE=panache45] The closest would be Hilo, which isn’t in the lava’s path. [/QUOTE] This [link](http://pubs.usgs.gov/gip/hazards/mauna-loa.html) is a bit less sanguine: > [@](#): > > The most recent eruption of Mauna Loa occurred in 1984. This eruption originated at the summit and, within a few hours, migrated to the northeast rift zone. The resulting lava flows advanced to within 4 miles of Hilo before the 3-week-long eruption ended. Similar short-duration eruptions of Mauna Loa’s northeast rift zone in 1852 and 1942 produced flows that came within about the same distance of Hilo. In 1855, a much longer-lived eruption fed a flow that stopped half a mile east of the upper Kaumana area on the western outskirts of modern Hilo. Lava invaded the present boundaries of Hilo in 1881, although the flow did not reach the shoreline, where the village of Hilo was located at that time. ---
**Author:** ![Cunctator](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Cunctator](https://boards.straightdope.com/u/Cunctator)\ **Post date:** [May 10, 2007, 1:20am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/11 "2007-05-10T01:20:38Z")
[Auckland?](http://en.wikipedia.org/wiki/Auckland#Volcanoes) It straddles a dormant volcano field. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [May 10, 2007, 1:42am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/12 "2007-05-10T01:42:55Z")
[QUOTE=A.R. Cane] Mt. Hood lies immediately south of the Columbia river, if an eruption were to block the river, a likely scenario, the resulting flood would be catastrophic for a large metropolitan area. [/QUOTE] The summit of Mt. Hood is nearly 20 miles from the Columbia as the crow flies, and more if you follow the historical lahar flows to Hood River, so blocking the Columbia would [be a 100,000 year event](http://pubs.usgs.gov/fs/2000/fs060-00/), : > [@](#): > > About 100,000 years ago, a large portion of the volcano’s north flank and summit collapsed. The resulting debris avalanche transformed into a lahar that swept down the Hood River valley. At the river’s mouth, where the town of Hood River now stands, the lahar was 400 feet deep. The lahar crossed the Columbia River and surged up the White Salmon River valley on the Washington side. Since that time lava has filled in the scar left by the debris avalanche. > > On the south side of the volcano, the scar from a 1,500-year-old debris avalanche is still visible, forming the amphitheater around Crater Rock. A lahar formed by this event traveled the length of the Sandy River valley, depositing boulders as large as 8 feet in diameter, 30 feet above present river level where the towns of Wemme and Wildwood now stand. The lahar spread out over the delta at the mouth of the Sandy River and pushed the Columbia River to the north. This event, although large by Mount Hood’s standards, was only about one-tenth the size of the 100,000-year-old event. > > Mount Hood’s next eruption is much more likely to be smaller than or similar in size to the 1,500-year-old event. **An eruption similar in size to the 100,000-year-old event, although possible, is much less likely**. There is big difference between affecting the flow and blocking the river. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [May 10, 2007, 2:48am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/13 "2007-05-10T02:48:32Z")
Is Reykjavík (Iceland) at risk? I know Iceland is a volcanic hot spot. Also, I don’t know whether [Volcán de Agua](http://en.wikipedia.org/wiki/Volc%C3%A1n_de_Agua) is close enough to threaten Guatemala City. [Volcano Masaya](http://en.wikipedia.org/wiki/Masaya_Volcano) is 20 km from Managua, Nicaragua. Its eruption in 4550 B.C. was one of the largest on Earth in the last 10,000 years. [Cite](http://volcano.und.edu/vwdocs/volc_images/south_america/masaya.html). ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [May 10, 2007, 2:55am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/14 "2007-05-10T02:55:23Z")
Also, [Ilopango](http://volcano.und.edu/vwdocs/volc_images/south_america/el_salvador/ilopango.html) is close by San Salvador, El Salvador. It was the site of a massive eruption in AD 260. ---
**Author:** ![jovan](https://avatars.discourse-cdn.com/v4/letter/j/0ea827/32.png) [@jovan](https://boards.straightdope.com/u/jovan)\ **Post date:** [May 10, 2007, 3:40am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/15 "2007-05-10T03:40:09Z")
[QUOTE=Polycarp] Likewise two volcanoes directly adjacent to Kyoto and within fairly close proximity to Osaka. [/QUOTE] I don’t know where you got that, but there are no volcanoes “directly adjacent” to Kyoto. Take a look at [this map](http://terra.sgu.ac.jp/river/Volcano/VolMapJapan.jpg), which shows Japanese volcanoes. The closest volcanoes are those of the Kannabe group, in northern Hyogo Prefecture, and that’s quite a way from the big Kobe-Osaka-Kyoto sprawl. By contrast, the Kanto plain, where Tokyo is, is literally surrounded by volcanoes, some of them, like mount Asama, are quite active. I _have_ to mention the city of [Kagoshima](http://maps.google.com/maps?f=q&hl=en&q=&ie=UTF8&ll=31.570053,130.594139&spn=0.147426,0.22831&t=k&z=12&om=1). It’s on the left of this satelite image. On the right, is the island of Sakura-jima, home to the Ontake volcano. Here are a few quaint pictures of Sakura-jima: [http://storage.kanshin.com/free/img\_31/315536/k1074144041.jpg](http://storage.kanshin.com/free/img_31/315536/k1074144041.jpg) > **[土砂災害防止広報センター - 土砂災害防止広報センター](https://www.sabopc.or.jp/)** [![](http://www.datejozo.co.jp/img/sakurajimab1.jpg) ](http://www.datejozo.co.jp/img/sakurajimab1.jpg) [![](http://www.yado.co.jp/kankou/kagosima/oosumi/sakurajm/sakurajm01.jpg) ](http://www.yado.co.jp/kankou/kagosima/oosumi/sakurajm/sakurajm01.jpg) ---
**Author:** ![Geek\_Mecha](https://avatars.discourse-cdn.com/v4/letter/g/ecae2f/32.png) [@Geek\_Mecha](https://boards.straightdope.com/u/Geek_Mecha)\ **Post date:** [May 10, 2007, 4:13am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/16 "2007-05-10T04:13:22Z")
[QUOTE=Xema] This [link](http://pubs.usgs.gov/gip/hazards/mauna-loa.html) is a bit less sanguine: [/QUOTE] **panache** was talking about Kilau’ea, though; your link is about Mauna Loa. There are three volcanoes on the island of Hawai’i: Kilau’ea, Mauna Kea, and Mauna Loa. Mauna Kea, which is home to an observatory, is extinct. Kilau’ea is an active volcano, though it _oozes_ more than it _erupts_. All of the major towns on the island (nothing there really can be described as a city) are pretty much on the opposite side of the island. [This map](http://www.nps.gov/havo/planyourvisit/upload/map_islandcolored_2005_300dpi_lg.jpg) shows where the three lie in relation to one other. The town of Hilo is on the northeast coast of the island and closer to Mauna Loa and Mauna Kea. It’s easy to see how lava flows would endanger the Hilo, as well as Waimea and Kailua-Kona. Kilau’ea, however, is basically right on the coastline and threatens nothing. When lava does threaten homes, it does so at a sluggish pace. Hawaii is not as populated as Oahu or Maui, and IIRC that area is very rural. The number of people whose homes are endangered by Kilau’ea is pretty darn small. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 10, 2007, 5:06am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/17 "2007-05-10T05:06:34Z")
[QUOTE=AudreyK] **panache** was talking about Kilau’ea, though; your link is about Mauna Loa. [/QUOTE] Well, lava is pretty much lava, capable of endangering towns regardless of the name of the hill from which it flowed. > [@](#): > > Kilau’ea, however, is basically right on the coastline and threatens nothing. It has done a fairly good job of threatening Kalapana (pretty well wiped it out in 1990). ---
**Author:** ![matt\_mcl](https://avatars.discourse-cdn.com/v4/letter/m/7ab992/32.png) [@matt\_mcl](https://boards.straightdope.com/u/matt_mcl)\ **Post date:** [May 10, 2007, 5:16am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/18 "2007-05-10T05:16:41Z")
Incidentally, there’s a myth that Mount Royal in Montreal is an extinct volcano. Actually it appears to be a magma intrusion, a site where magma seeped into the earth’s crust and solidified, before the overlying rock was eroded, exposing the mountain. No danger there. ---
**Author:** ![CairoCarol](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cairocarol/32/3825_2.png) [@CairoCarol](https://boards.straightdope.com/u/CairoCarol)\ **Post date:** [May 10, 2007, 7:10am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/19 "2007-05-10T07:10:52Z")
> [@](#): > > There are three volcanoes on the island of Hawai’i: Five actually: Mauna Loa Mauna Kea (extinct) Kilauea (erupting continuously since 1983) Hualalai Kohala (extinct) ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [May 10, 2007, 8:00am UTC](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446/20 "2007-05-10T08:00:27Z")
Further to **jovan** ’s observation, I actually lived in Kagoshima for a couple of months in the early 1990s. The volcanic ash fell like snow daily, covering cars and houses and trees - sometimes an inch deep. The volcano’s name, Sakura-jima, means “Cherry blossom island”. It isn’t an island, though, due to a massive eruption in the 1920s that created a land bridge to the mainland. You can take a bus tour of the volcano’s lower slopes, in which you can see abandoned temples embedded about six feet deep in pyroclastic debris. Well worth a visit! [Next page](https://boards.straightdope.com/t/what-big-cities-are-most-at-risk-from-volcanoes/403446.md?page=2)