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Offline tony6789

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« on: 14/05/2007 16:35:55 »
how sure are we that we have discovered every island etc.? wat if there is others?


 

Offline Ben6789

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« Reply #1 on: 14/05/2007 16:38:21 »
We have basically spilled over the entire globe and with airplanes crisscrossing the sky, and boats crisscrossing the sea, i'm pretty sure we have found every island man.
 

another_someone

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« Reply #2 on: 14/05/2007 17:24:37 »
Yes and no.

We have mapped all of the major land masses of the world; but that is not to say that we necessarily have mapped every small rock that dares expose its face above the waves.

Beyond that, islands are constantly being created (and destroyed).

Volcanoes will create new islands that were not there last time we looked.

Although the general expectation is that overall sea levels will rise, but any fall in sea level will expose more land.  In particular, even though the oceans might rise, there are many inland seas where sea level is actually falling.

Even as the oceans rise, although they may not expose more land, but land that previously had been linked to the mainland as part of a peninsula might become cut off as the peninsula is flooded, leaving an isolated island (or maybe several islands) along what were the highlands of that peninsula.

Earthquakes can cause shifting of land masses, and can cause an island to rise out of the sea.

Sand banks will shift, and rise and fall, and so can create new islands.

An unusually low tide might expose an area of land for a few hours, and when the tide comes in again, so the land will be covered again.
 

Offline Jenguin

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« Reply #3 on: 14/05/2007 19:24:51 »
A good example of islands being created and destroyed is in the Galapagos Islands.  Because there is a hotspot in this area of the world, volcanoes tend to occur, which causes islands to form.  Because this area is prone to a high rate of Continental Drift because of the geography of the area, these islands move away from the hotspot and become cold and other islands are created in place.  Eventually these cold islands reach a subduction zone and the island becomes smaller as they are drawn back into the Earth.

I think this is how it works, but it is becoming longer and longer since I was in school :D.  Googling it would have been cheating, though!
 

Offline tony6789

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« Reply #4 on: 15/05/2007 16:21:29 »
so maps are changinng monthly im guessing?
 

Offline Ben6789

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« Reply #5 on: 15/05/2007 16:33:22 »
Oh gosh no, not monthly. Try every Century.
 

Offline ichnos

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« Reply #6 on: 15/05/2007 17:07:42 »
for example the island of Surtsey off the south coast of iceland formed between 1963 and 1967 from a series of volcanic eruptions. The island is the size of 1.4 km2 already diminished from around 2.7 km2 at the time of formation.. so islands- even fairly large ones can come and go pretty rapidly! 

 

another_someone

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« Reply #7 on: 15/05/2007 17:22:14 »
It depends on what it is you are trying to map out.

The practicalities of making a map means that they would only produce a new one every few years.

The biggest risk to shipping is wrecks, which in a way can be regarded as very small artificial islands (maybe sully submerged, so not really islands as such, but nonetheless navigational features that need to be recorded; but sometimes they will be above the surface).  Also, you have other types of artificial islands, such as oil rigs in the sea.  These clearly happen far more frequently than every century (in fact, not one of the oil rigs we have in the North Sea is over 40 years old, and most will probably not be there in 40 years time).

Volcanoes can create islands fairly fast, although the number that create absolutely new islands is rare, but more commonly they might change the shape of an existing islands.  It is likely that new islands created in this way would not be more than one or two a century (although I am not sure about the exact frequency).

Changes in island formation due to changes in sea level (particularly if one includes inland seas and lakes) can be quite frequent, and I would guess we are talking more about a decade or two rather than centuries (assuming we ignore causeways that are flooded at high tide - if we were being absurdly literal, one could argue that in these cases, we have an island being formed and destroyed twice each day).

 

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« Reply #7 on: 15/05/2007 17:22:14 »

 

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