[HN Gopher] Bifurcation: The secret giant islands formed when ri...
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Bifurcation: The secret giant islands formed when rivers split
Author : webstrand
Score : 79 points
Date : 2025-02-26 15:58 UTC (7 hours ago)
(HTM) web link (starkeycomics.com)
(TXT) w3m dump (starkeycomics.com)
| Retric wrote:
| It's surprising how common this is.
|
| Other examples:
| https://en.wikipedia.org/wiki/River_bifurcation#Examples
| jetrink wrote:
| The article that follows that one is also very interesting and
| worth reading. It shows how a coastline that existed 100 million
| years ago and cut through modern day Alabama is still visible in
| demographic and election maps. (By a crazy coincidence, I just
| dug up that article and sent it to someone not even half an hour
| ago, since we were talking about geology and I remembered reading
| it. Then I go to HN and see this posted.)
|
| 1. https://starkeycomics.com/2021/06/11/how-a-
| coastline-100-mil...
| orangesun wrote:
| Synchronicity
| debacle wrote:
| An interesting phenomenon. I remember reading similar articles
| about how, in older cities, the closer you lived to the water
| the more poor you were, but in newer cities the opposite is
| true. This rings true for many rust belt cities, and it makes
| gentrification a complex issue because public housing tends to
| have been built on what has become some of the most expensive
| real estate today.
| arcticfox wrote:
| Very cool, I just learned about these recently. I wonder, at what
| point does something become not eligible to be an island? Like,
| that biggest island looks like almost half of North America.
| Doesn't that make the other half an even bigger island?
| slongfield wrote:
| The parting of the waters in the USA is such an interesting
| landmark for just how uninteresting it actually is in person.
| Looks like any other split in a forest river, marked by a sign on
| a tree that you can only see after a long wilderness hike.
|
| https://en.wikipedia.org/wiki/Parting_of_the_Waters
|
| https://www.anotherlongwalk.com/2022/07/day-119-parting-of-w...
| elf25 wrote:
| Bifurcation occurs at the Great Lakes, where the Mississippi
| flows into the gulf and the St. Lawrence empties into the
| Atlantic. This forms the "great loop", a circumnavigation course
| known by many power boaters . This makes about half of the United
| States and island by your definitions.
| bryanlarsen wrote:
| The Chicago - Great Lakes connection is man made, so doesn't
| count per the methodology of the OP.
| Nevermark wrote:
| So North and South America are not the North and South Panama
| Canal Islands. Got it!
| kibwen wrote:
| Most of the population of Bangladesh lives on what is technically
| an island created by the forking of the Brahmaputra, whose
| distributaries rejoin 150 miles away (as the crow flies).
| https://en.wikipedia.org/wiki/Brahmaputra_River#Bangladesh
| jameshart wrote:
| This is not to take away from the fun of investigating and
| identifying these 'bifurcation islands', but on the question of
| whether they qualify as 'islands':
|
| > Like a delta island, it is surrounded entirely by sea and
| rivers. As an area of land separate from a continent, permanently
| and entirely surrounded by water, it seems to fit every
| definition of an island I can find.
|
| I agree that by 'Air Bud' rules these qualify as islands ('ain't
| no rule says an island can't have one end halfway up a mountain
| and the other at sea level') but I think there is a reason why we
| don't instinctively feel like they qualify as 'proper islands'.
|
| Specifically, I think the instinctive definition of an island is
| that it emerges from the water surrounding it at a _consistent
| elevation_. It has a shoreline that is broadly level.
|
| The delta islands that he identifies as being basically the same
| as bifurcation islands are typically surrounded by tidal water on
| all sides so their shoreline is all at sea level.
|
| Counterpoint, though: Goat Island, which is in the middle of
| Niagara Falls, and has one end at the elevation of Lake Erie and
| the other at the lower elevation of Lake Ontario. Does this feel
| like a 'proper island'? I know in my mind I sort of struggle to
| think of Goat Island as being an island, not two islands that
| happen to be right next to one another... but I can adjust my
| mental definition of island to account for it; but extending it
| to the continent-spanning bifurcation islands still feels too
| much of a stretch.
|
| This is like the 'dwarf planet' problem - there wasn't a good way
| to make Pluto a planet without making a lot of things that
| definitely aren't planets also count as planets.
|
| Is there a good way to make Goat Island an island, without also
| making the bifurcation islands into islands?
|
| Also... Australia is clearly an island by this definition. But
| then so is Antarctica.. and the entire Americas. And the
| Eurasian/African supercontinent...
| rusk wrote:
| Presumably (with little more than an 8 y/o grasp of astronomy),
| Pluto's orbit being consistent with the other heliocentric
| planets gave it an extra qualifier?
| Retric wrote:
| It's not consistent with the other planets though. Mercury is
| off by 7 degrees, the other planets are within 3.
|
| Pluto meanwhile is 17 degrees off the ecliptic so it's a
| serious outer.
| BurningFrog wrote:
| I resolve these things is by remembering that words are only
| approximate definitions of real world concepts.
|
| This means there will always be a fuzzy area where it's not
| clear if the word covers it or not. I recommend not trying to
| determine _exactly_ what the boundaries of the word are. Try
| using more /other words instead.
|
| This may be an easier thing to internalize when you know more
| than one language.
| jameshart wrote:
| I'm extremely comfortable with fuzzy boundaries but the
| article in question literally invites the subject of 'why are
| these things islands and these other things not?'
| BurningFrog wrote:
| OK, That's a relevant context that I missed.
| madcaptenor wrote:
| Wikipedia's list of islands
| (https://en.wikipedia.org/wiki/List_of_islands_by_area) starts
| with a separate table for "continental landmasses", containing
| Afro-Eurasia, the Americas, Antarctica, and Australia.
| Australia is ~3.5 times the size of Greenland (the #5 landmass)
| so between Australia and Greenland seems a nice place to draw
| the lint.
|
| But Greenland is in turn ~2.5 times the size of #6 New Guinea.
| Maybe if Greenland were more populated (let's imagine, say,
| that the Earth's axis is positioned differently so that it's
| warmer there) it would be considered a continent?
| poizan42 wrote:
| Maybe a more natural way to make the distinction is by looking
| at the average width of the body of water seperating the
| landmass relative to the area of the landmass. That is an
| island is a landmass that has an area (A) of at least A_min and
| at most A_max and is either
|
| a) Surrounded by a body of water with average width W_avg where
| W_avg > f_min*sqrt(A) - or
|
| b) Surrounded by a body of water with average width W_avg where
| W_avg > W_min
|
| Fill in the constants A_min, A_max, f_min and W_min to get as
| close as possible to real world usage of the word "island".
| eesmith wrote:
| I'm quite taken by your Goat Island example - thanks for
| mentioning it!
| npodbielski wrote:
| I though this about running multiple nvme disks on single PCIE
| slot. https://www.asus.com/support/faq/1037507/
| hydrogen7800 wrote:
| > The Missouri is the largest tributary of the Mississippi River,
| which flows into the Gulf of Mexico
|
| He must mean longest. This chart[0] shows that the Ohio is by far
| the largest tributary of the Mississippi by volumetric flow, and
| also shows the Atchafalaya bifurcation. However, the wiki
| articles for the Missouri[1] and Ohio[2] show average discharges
| into the Mississippi of 87,520 cu ft/s and 281,000 cu ft/s,
| respectively. Not as great a difference as the first chart [0]
| shows, but still significantly different. Even more interesting,
| since the Missouri drainage basin is about 2.5x larger.
|
| [0]https://en.wikipedia.org/wiki/Mississippi_River#/media/File:..
| .
|
| [1]https://en.wikipedia.org/wiki/Missouri_River
|
| [2]https://en.wikipedia.org/wiki/Ohio_River
| spencefu wrote:
| As always, there's an xkcd for that: https://xkcd.com/2838/
| BurningFrog wrote:
| As a kid I found a bifurcation island in northern Sweden, that
| may be bigger than Gotland, the conventionally biggest island in
| Sweden.
|
| It's formed by the Tarendo River which flows from the Torne river
| to Kalix river.
|
| It's supposedly the second biggest bifurcation in the world:
| https://en.wikipedia.org/wiki/T%C3%A4rend%C3%B6_River
|
| This is the best image I found:
| https://www.smhi.se/polopoly_fs/1.30940.1490013619!/image/%C...
| EdwardDiego wrote:
| I live near what used to be several of these - Kaiapoi
| Island,Coutts Island, McLeans Island, Templar Island, no doubt
| forgetting some.
|
| Created by the Waimakariri River splitting into 3 branches as it
| neared the ocean.
|
| They're no longer islands as the two side-branches of the river
| caused repeated severe floods in colonial days, so large civil
| engineering efforts went into restraining the river, ultimately
| leading to the south branch and north branch being blocked by
| large stopbanks and riprap cassions.
|
| Both branches were then utilised to drain water from high
| fertility but swampy ground.
|
| Because NZ's braided rivers lend themselves to wandering
| channels, we've still got some decent sized river islands -
| Rakaia Island, Rangitata Island.
| Onavo wrote:
| Lyapunov is calling and wants his terminology back.
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(page generated 2025-02-26 23:00 UTC)