Wikipedia:Reference desk/Archives/Miscellaneous/2022 September 26

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September 26

Continents

The list of topics by reference sub-desk doesn't include "geography", so I'm asking at Miscellaneous.

Why is Australia often listed as a continent (and not an island)? Surely the continent is Oceania which comprises the islands of Australia, New Zealand, Papua New Guinea and the many pacific islands. Quoting from continent, we have "Greenland, with a surface area of 2,166,086 square kilometres (836,330 sq mi), is only considered the world's largest island, while Australia, at 7,617,930 square kilometres (2,941,300 sq mi), is deemed the smallest continent." -- SGBailey (talk) 06:09, 26 September 2022 (UTC)

Hello, SGBailey. Let's use the definitions in the relevant Wikipedia articles as a start. Continent says Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. "Convention" is the word that leaps out there, and Convention says A convention is a set of agreed, stipulated, or generally accepted standards, norms, social norms, or criteria, often taking the form of a custom. and Island says There is no standard of size that distinguishes islands from continents

In other words, there is no universally accepted definition of "continent" or "island", although there is rough general agreement. One could reasonably argue that the Eurasian landmass is a gigantic island instead of two continents with an ill-defined boundary, and that what we commonly call North America, Central America and South America is the second biggest island on Earth, instead of two continents with some ill-defined "Central American" territory in-between. So. if you want to call Greenland and New Guinea "continents", go right ahead, but do not expect other people to agree with you. Cullen328 (talk) 06:48, 26 September 2022 (UTC)

You could also have put this in the "Language" desk, because this is just the convention that has arisen. Though I've often heard Australia referred to as the "island continent." Though if you stop and think about it, all of the continents are islands, i.e. the major land masses are all surrounded by water. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:54, 26 September 2022 (UTC)

When I was in school (a million years ago), it was drummed into us that "Australia is the world's largest island and smallest continent". Later, those better than I seem to have agreed among themselves that it has to be one or the other, not both. So, smallest continent it is. (But we're still bigger than Greenland, so nyah!.) -- Jack of Oz ^{[pleasantries]} 08:16, 26 September 2022 (UTC)

Most continents are actually not islands, as (apart from an artificial canal), Europe, Asia and Africa are a single "island", and the same goes for the Americas. If a (large) landmass surrounded by water was the definition of continent, we'd only have 4 of them... Rmvandijk (talk) 09:21, 26 September 2022 (UTC)

Or even just 2, as Australia and Antarctica are pretty dang small compared to the Eurafrasian and American landmasses and might then be considered just islands. --User:Khajidha (talk) (contributions) 11:55, 26 September 2022 (UTC)

Yes, apart from canals, North and South America make up one land mass, Europe-Asia-Africa make up another, and Australia and Antarctica stand alone, though geologists believe they were once together. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:28, 26 September 2022 (UTC)

• There is no well-agreed-upon definition of a continent, there is only what your teachers taught you in school, and that's just something some people made up too, and depending on where you went to school, there will be different lists of continents for different people. Historically, the concept of a continent was a cultural as much as geological one, the T and O map is one of the earliest attempts to identify the continents, outlining Asia, Africa, and Europe. --Jayron32 12:04, 26 September 2022 (UTC)

• By the way, if you think that artificial canals could be relevant to the boundaries of continents, you might also consider natural rivers that interconnect, like at the Casiquiare River: are Suriname and Ecuador really on the same land mass? For more examples see river bifurcation and list of unusual drainage systems. --174.95.81.219 (talk) 21:37, 26 September 2022 (UTC)

I think what irks me about all this is that it appears to me to be patently obvious that Australia is NOT a continent, it is a part of the same continent that includes New Zealand and Papua New Guinea et al. -- SGBailey (talk) 18:38, 26 September 2022 (UTC)i

What irks me is is the notion that every island must be considered part of some continent. What appears patently obvious to me is that New Zealand, for example, is not part of a continent. (This is not an attempt to debate; it's just pointing out that, as stated above, these things are not well agreed upon.) --174.95.81.219 (talk) 21:27, 26 September 2022 (UTC)

While to me it is patently obvious that NZ isn't part of any continent. New Guinea is already included in the continent of Australia. And, as for the various islands of the Pacific, including them in any continent is beyond ridiculous.--User:Khajidha (talk) (contributions) 21:32, 26 September 2022 (UTC)

Well, obviously there are no such things as either islands or continents, just tectonic plates, parts of which stick up high enough to stay dry. Just because two plates ram into each other hard enough to raise very high mountains is no reason to suppose they are in any way connected. And if two dry bits are both on the same plate, there can be no question of making any possible distinction between them. (Runs off to hide behind Mid-Atlantic Ridge) -- Verbarson  ^talk_edits 22:07, 26 September 2022 (UTC)

New Zealand is part of the continent of Zealandia, which happens to be mostly underwater. Lots of deep ocean between there and Australia, so no question of Australia and NZ being in the same continent. --Trovatore (talk) 22:25, 26 September 2022 (UTC)

• Etymologically, "continent" implies a large, continuous, uninterrupted landmass. While geopolotically island nations are often grouped together with nearby continents, in physical geography a collection of small scattered islands, such as Oceania, is the exact opposite of that notion (e.g. climates in continental interiors are different than those in small islands). --Theurgist (talk) 23:23, 26 September 2022 (UTC)

Crust thickness in kilometers

Take a gander at this map, taken from our article on continental crust. If you look at the thickness of the crust, and don't get distracted by superficial water, it seems very defensible to argue for five continents (or four, if you think Australia is too small): Afro-Eurasia; North America (which includes Greenland); South America; Antarctica; Australia. The division between North America and South America is not the trivial trickle of the Panama Canal, but the fact that the Isthmus of Panama is just a narrow little strip and the crust there is really not very thick anyway. --Trovatore (talk) 00:39, 28 September 2022 (UTC)

I probably ought to offer a couple of caveats. One is that the color does not seem to correspond exactly to the crustal thickness — I think the color is more likely elevation/depth of land/sea. The other is that there's an artificial division imposed by where the map is divided, and you could make a case for joining North America to Afro-Eurasia on the grounds that the crust is fairly thick at the Bering Strait — but on that point I would point out again that any such junction would be very thin, and I think you don't need to connect continents that just barely touch. --Trovatore (talk) 04:39, 28 September 2022 (UTC)