Geoligists Wanted: Need help for Fictional Island

[Crossroads Inc.]

AHoy!

I am in the process of a series of short fiction stories that take place on the following island:
Tilted shot using SimCity to scuplt it
Unfinished Topographical view, again using SimCity

The island itself fits it prominently with the stories and in order to have the properly needed realism, I figured on asking anyone with advanced knowledge in Geology or Earth Science a few questions.

Basically, the island, at it's longest, is just over 8miles across. the single mountain is all thats left of a massive volcano that formed the island long ago. The southern edge of the island was "blown out" during it's last eruption, crating the 'St.Helans' type eruption and leaving the smaller island inside the cauldron.

Basically what I want to know is first off, is such an event even possible? At least in regards to creating an island that looks just like the one I have. Also, what sort of minerals/gems/resources would you expect would form on an island with such a history?

[Sea Skimmer]

Normally when you've got an island in the middle of a volcanic crater, its not 'left over' from a giant explosive eruption, but rather the result of lava building up from later lesser eruptions. Anyway I'm not a geologist, but outwardly I don't see anything questionable.

[Crossroads Inc.]

Edit: Ok first off, remind me to stop using Geoshities to host pics, and wait for me to get a Photobucket account...

[Crossroads Inc.]

EDIT: Ok, photos fixed.. can a kind Mod change the links at the top to the ones below?


Unfinished Topographical view, again using SimCity
Tilted shot using SimCity to scuplt it

[Elheru Aran]

I see nothing wrong with it.

Though like Skimmer said, most 'islands' inside volcanic craters are *not* material left over from the explosion; they're the solidified lava crust lifted up by the pressure of the magma underneath. Look up Crater Lake in Oregon; it's got an island in the middle that's formed by just such an geological phenomenon.

Otherwise you're cool.

[Crossroads Inc.]

Ok, sounds good. The 'Island' in the middle, if it's just solidified lava, given enough years ((say about 10,000 which is when it last erupted)) would there be enough topsoil for moss and trees and such to grow on it? I wanted to have various hot water springs coming up in the middle and around the inner cauldron heated by the magma well underneath.

Also, and this is the main thing I’m wondering about when im looking to what types of rocks, minerals, resources would exist on such an island... Is that, could the island be self-sustaining to a population (early 1800 tech level) of about, oh, 5,000 to 8,000?

I've been reading up on several Pacific islands, such as Easter, where the advancement of population was so fast that it stripped an island bare.

[Master of Ossus]

I wanted to have various hot water springs coming up in the middle and around the inner cauldron heated by the magma well underneath.

That would actually be kinda surprising unless the island was still volcanically active.

Also, and this is the main thing I’m wondering about when im looking to what types of rocks, minerals, resources would exist on such an island... Is that, could the island be self-sustaining to a population (early 1800 tech level) of about, oh, 5,000 to 8,000?

Easter Island is 64 square miles, and supported a population of about 10,000. Remember, also, that Easter Island had absolutely pathetic levels of agricultural development and no ability to use deep-sea fish after the islanders wiped out all the trees. An island of 5,000 people is no problem for this, assuming that they still have trees and such. Depending on how close to the equator the thing is, it could also have native or feral animals that would be sufficient for limited hunting, and fish farming and agriculture can be very developed on larger islands like this one, and agriculture can be very developed on islands in general.

I've been reading up on several Pacific islands, such as Easter, where the advancement of population was so fast that it stripped an island bare.

That was true of Easter Island, but in general islands with large wilderness areas were able to resist people. It looks like parts of your island would be inhospitable (largely because prevailing ocean currents would cut the rocks on at least one side of the island and make it difficult to form harbors or fish from), so that shouldn't be nearly as much of an issue where you are. The difficulty on Easter Island was largely a product of the homogenous geographical area--the entire island was basically all forested when humans arrived, with only a few rocky outcroppings that housed seabirds and such. Of the 9 criteria that Jared Diamond suggests hastens the demise of forests on Pacific Islands, Easter Island had eight.

[Broomstick]

Ok, sounds good. The 'Island' in the middle, if it's just solidified lava, given enough years ((say about 10,000 which is when it last erupted)) would there be enough topsoil for moss and trees and such to grow on it?

Could be.

A lot depends on the type of lava flows you'd get from it. Get a book on the Hawaiian islands and read up on them. Their soils range from rich, fertile stuff to lava fields that are unbroken, impenetrable rock

I wanted to have various hot water springs coming up in the middle and around the inner cauldron heated by the magma well underneath.

Possible, but it would mean the island is still volcanically active. You'd probably also have some sort of occassional lava flow, outgassings, and the like.

The problem is that volcanos can change only so much - one prone to explosive outbursts is most likely to continue with such eruptions. It's not going to suddenly become a nice, tame caldera like the one on the big island of Hawaii where the lava flows to the sea without explosive pyrotechnics.

Also, and this is the main thing I’m wondering about when im looking to what types of rocks, minerals, resources would exist on such an island... Is that, could the island be self-sustaining to a population (early 1800 tech level) of about, oh, 5,000 to 8,000?

Rocks: volcanic, of course, basalts and various metamorhpic rocks, some of them quite hard. Others, like pumice, much less dense. Obsidian/volcanic glass, which can be quite useful and valuable.

If the island has been stable long enough you could have extensive coral reefs, which are full of calcium carbonate.

I don't think you're going to find deposits of iron ore, or copper, silver, gold... not in anything greater than trace quantities. Your islanders could trade for metal, though.

Might have quite a bit of sulfur lying about, depending on the composition of the magma that created the island.

Other resources... if you want to have people, you'll need a reliable source of fresh water. You'll need edible plants. You need some source of protein for people - fish will do fine, but also seabirds. Your island is a little small to support livestock. Shells from shellfish can be very useful tools, and also provide things such as pearls, mother of pearl, abalone shell, and other materials that are ornamental as well as useful

Jared Diamond's latest book, Collapse, discusses not only Easter Island and others where a civilization fell or entirely disappeared, it also covers islands that have sustained their populations in a stable manner for hundreds of years.

All of the long-term successful societies practiced population control of one form or another.

And that brings up the point that the culture of a small island is as important as the resources available on it. Unchecked population growth and/or greed can destroy an island society just as quickly as any other disaster.

[Crossroads Inc.]

Hey, thanks to all the great feed back so far!

The island, climate wise, is about upper northwest, if I had to give a comparison, I'd say similar weather to off the cost Oregon. So the upper mountain would be heavily wooded with thick forests.

I wanted to have various hot water springs coming up in the middle and around the inner cauldron heated by the magma well underneath.

That would actually be kinda surprising unless the island was still volcanically active.

Well, It's a shame I can't have it both ways. Would like geothermal activity and hotsprings... but for safety of Island, not have it active. Maybe I can just make it "Very Dormant"

That was true of Easter Island, but in general islands with large wilderness areas were able to resist people. It looks like parts of your island would be inhospitable (largely because prevailing ocean currents would cut the rocks on at least one side of the island and make it difficult to form harbors or fish from)

I thought about this, and ((if I'm correct)) the bay I added in the northern section should provide a protected harbor for fishing and boats or making boats ((since this is also where I planed on having one of the two main villages.))

, so that shouldn't be nearly as much of an issue where you are. The difficulty on Easter Island was largely a product of the homogenous geographical area--the entire island was basically all forested when humans arrived, with only a few rocky outcroppings that housed seabirds and such. Of the 9 criteria that Jared Diamond suggests hastens the demise of forests on Pacific Islands, Easter Island had eight.

It was reading Jared Diamonds book, mainly in research for my stories that led me to question the islands feasibility in the first place. So far things look good. [/quote] Thank you muchly! Glad to see how much feed back.

The problem is that volcanos can change only so much - one prone to explosive outbursts is most likely to continue with such eruptions. It's not going to suddenly become a nice, tame caldera like the one on the big island of Hawaii where the lava flows to the sea without explosive pyrotechnics.

Yea, Ossus mentioned the same thing. Either I'll have to make this dead, and loose hot springs, or have occasional outbursts... Will have to work on this more.

If the island has been stable long enough you could have extensive coral reefs, which are full of calcium carbonate.

I don't think you're going to find deposits of iron ore, or copper, silver, gold... not in anything greater than trace quantities. Your islanders could trade for metal, though.

Might have quite a bit of sulfur lying about, depending on the composition of the magma that created the island.

Well, given the colder climate I don't think Coral reefs would develop as they need warm waters (I think). Not many metals IS going to be a problem, I had hoped the ancient volcanism would stir up some useable resources and metals, but if not that could be a BIG problem as the islanders can't exactly trade easily...

Other resources... if you want to have people, you'll need a reliable source of fresh water. You'll need edible plants. You need some source of protein for people - fish will do fine, but also seabirds. Your island is a little small to support livestock. Shells from shellfish can be very useful tools, and also provide things such as pearls, mother of pearl, abalone shell, and other materials that are ornamental as well as useful

The waters around the island are quite shallow, and there would be more then enough rainstorms that there would be plenty of fresh water rivers coming down from rainfall. Also theres large tidal areas, all the land that’s 'brown' in that over head shot is stuff thats under water at High tide.

[Instant Sunrise]

Maybe you could stick a rift valley in the middle of it where new seafloor is being created. A'la Iceland.

[CaptainChewbacca]

If you've got a crater that big, it might be a caldera, in which case it would be on a "hot spot" and have plenty of geothermal springs and activity ALA yellowstone. The lagoon in the middle would be very rich in animal life.

Wizard Island, in Crater Lake Oregon, is not a new volcanic vent, but is in fact debris left over from a massive eruption followed by several smaller ones. It has since been quiet.

I imagine the geology of such an island is composed of vertical sheet dikes of non-porus lava interbedded with very porus ash material. There won't be much in the way of mineral resources on the island unless you get lucky and there's a hydrothermal copper vein running through one of the interbeds. There will be MANY hot springs on that island, and you can decide where they are depending on the migration of the island over the hot-spot. There would be alot of obsidian, but if its a cool climate the trees will likely be sequoia, as they have a shallow-root system that other evergreens do not.

The central island can definitely have vegetation, both moss and trees. I believe a caldera can solve alot of your problems.

[tharkûn]

If you are really worried about a lack of metal you might stretch things by including a meteorite like the Cape York Meteorite which supplied the Inuit with several tons worth of iron and nickel. The odds that a small volcanic island would also be the resting place of a massive, high metal content meteorite are low, but within the the realm of possibility.

[CaptainChewbacca]

If you are really worried about a lack of metal you might stretch things by including a meteorite like the Cape York Meteorite which supplied the Inuit with several tons worth of iron and nickel. The odds that a small volcanic island would also be the resting place of a massive, high metal content meteorite are low, but within the the realm of possibility.

Actually, another good source of metals could be in iron-rich pillow-basalt deposits on the northern shore. Ophiolites can often have metal veins in them, though the iron isn't very good-quality.

[Master of Ossus]

If you are really worried about a lack of metal you might stretch things by including a meteorite like the Cape York Meteorite which supplied the Inuit with several tons worth of iron and nickel. The odds that a small volcanic island would also be the resting place of a massive, high metal content meteorite are low, but within the the realm of possibility.

The Egyptians also used meteorites as a source of iron, but on a vegetated island finding these things is going to be frickin' difficult. It was easier in the snow and the desert sands, where they stick out pretty badly.

[Instant Sunrise]

What kind of minerals come out of oceanic ridges?

Because placing a hot-spot under a spreading oceanic ridge could solve your problems. a smaller, younger, Iceland in a different spot, basically.

[tharkûn]

The Egyptians also used meteorites as a source of iron, but on a vegetated island finding these things is going to be frickin' difficult. It was easier in the snow and the desert sands, where they stick out pretty badly.

Not for a truly large impact that hasn't seen geologic scale weathering. Find the impact crator, proceed to center, dig. I'm not talking about finding a bunch of small meteorites pelted down helter skelter, but one massive one in its impact crator. Once somebody finds it, for whatever reason, they will be able to keep coming back to it.

[Elheru Aran]

Why come back? Enough men and enough rope... do it Egyptian style, baby...

[Crossroads Inc.]

You know, I've been wondering if the massive 'Crater' that I had explained as a Volcanic eruption, perhaps could have been made by a Meteorite... But going from what I'm now hearing, I will be able to give the island more resources then it originally seemed.

All in all this will be interesting given the concept behind my back and the nature of things... See, this island, about 8,000 years ago, is swallowed up in the worst pan-dimensional rip in the Fabric of the cosmos. The island, along with several thousand kilometres of rock, magma, and seawater, ended up in a pocket dimension. This PD was in the middle of a nexus of other Rifts and portholes that made it a 'crossroads' of portholes that linked to planets all over the galaxy. Slowly, different alien races and peoples came there and where forced to build a civilization.

This was become no one ever came willingly, Ships 'lost' at sea would appear there, as would early airplanes, vehicles... All manors of things carrying people that where swallowed up by a rough Rip in space-time.

The story itself follows a group of humans on a Yacht who find themselves at the island after a storm in the Bermuda triangle...

Nifty backdrop for a story, no?

[CaptainChewbacca]

Well, if it was in a "pocket dimenstion" the interior of the island could be perforated with tiny pockets of matter from other times, places, and dimensions. How's a "plasma" mine grab ya?

[Broomstick]

This was become no one ever came willingly, Ships 'lost' at sea would appear there, as would early airplanes, vehicles... All manors of things carrying people that where swallowed up by a rough Rip in space-time.

That could give you some very interesting sources of materials/items that wouldn't be naturally found on an island.... and their limited supply could lead to some interesting conflicts.

The story itself follows a group of humans on a Yacht who find themselves at the island after a storm in the Bermuda triangle...

Nifty backdrop for a story, no?

Sorty of like Gilligan's Island with bug-eyed monsters?

[Crossroads Inc.]

Well, if it was in a "pocket dimenstion" the interior of the island could be perforated with tiny pockets of matter from other times, places, and dimensions. How's a "plasma" mine grab ya?

Wouldn't that hurt a lot? In seriousness though... The portals that attach to the island only appear over water or in the air. So anything comming through would only be from something along those lines ((hence the reason I wanted to know what the island would have, otherwise I could have 'cheated' and given it any resources I wanted.))

This was become no one ever came willingly, Ships 'lost' at sea would appear there, as would early airplanes, vehicles... All manors of things carrying people that where swallowed up by a rough Rip in space-time.

That could give you some very interesting sources of materials/items that wouldn't be naturally found on an island.... and their limited supply could lead to some interesting conflicts.

Hmmm, you havn't been looking at my rough drafts have you

[drachefly]

If they're in a PD, where's their sun? Why do they have gravity, if the rest of the Earth isn't there? Or does it swap around between planets, a la the castle in Krull, but more so and unintentionally?

On the other hand, PD-ness really handles the meteorite issue nicely.

[Crossroads Inc.]

If they're in a PD, where's their sun? Why do they have gravity, if the rest of the Earth isn't there? Or does it swap around between planets, a la the castle in Krull, but more so and unintentionally?

On the other hand, PD-ness really handles the meteorite issue nicely.

Um, yes, well.
<_<
>_>

Look, im trying to keep everything ELSE as realistic as possible, don't bother me with the facts

[Broomstick]

Sometimes, it's best not to explain too much. After all, the islanders themselves would have only limited resources to find out about their pocket world, correct?

Maybe they don't have a sun.... just some sort of misty sky that gets light and dark in a day cycle. Or maybe, if they do the planet-swapping thing, sometimes they have different suns (which might be interesting from a history/recordkeeping viewpoint..."In the time we had two suns..." or "When the sun was red instead of yellow....")

Ever play Myst? Interesting treatment of "pocket universes" there, some of them quite strange.