Beta

Slashdot: News for Nerds

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Hawaii's Oahu Used To Be a Bigger Island

timothy posted about 2 months ago | from the back-in-my-day-we-called-it-Oooooaaahhhuuu dept.

Earth 44

sciencehabit (1205606) writes "The two volcanoes long thought to have formed the Hawaiian island of Oahu had a head start: They grew on top of an older volcano that's now submerged northwest of the island and partially covered by it, new research suggests. Tests indicate that the long-lost peak—now dubbed Kaena volcano—grew from the sea floor and broke through the ocean's surface about 3.5 million years ago, eventually reaching a height of about 1000 meters above sea level before it began sinking back into the sea. At its largest, ancient Oahu would have measured about 1900 square kilometers (about 20% larger than modern-day Oahu) or larger. Over the course of its lifetime, Kaena volcano spilled between 20,000 and 27,000 cubic kilometers of molten rock, the researchers estimate. When Kaena volcano became largely extinct isn't clear."

cancel ×

44 comments

For the Americans (3, Funny)

Anonymous Coward | about 2 months ago | (#47083747)

27,000 cubic kilometers is 56608 gigabuttloads.

Re:For the Americans (2)

MightyMartian (840721) | about 2 months ago | (#47083917)

We prefer the teracrap measurement.

Re:For the Americans (-1)

K. S. Kyosuke (729550) | about 2 months ago | (#47083961)

In that case, those 56608 gigabuttloads translate to about 37.4 Obama speeches.

Re:For the Americans (-1)

Anonymous Coward | about 2 months ago | (#47084199)

In that case, those 56608 gigabuttloads translate to about 37.4 Obama speeches.

You missed the negative sign - that should be -37.4.

Those gigabuttloads actually exist. Not only that, if you like them you can actually keep them.

Re:For the Americans (0)

Anonymous Coward | about 2 months ago | (#47084499)

I wish Obama had kept his promise of sending all Republicans to Gitmo.

Re:For the Americans (1)

Anonymous Coward | about 2 months ago | (#47083963)

I prefer petacups, 114.1 petacups. I can 'feel' the size of a cup and I can count too 114 so it's easy to understand.

Re:For the Americans (1)

davester666 (731373) | about 2 months ago | (#47084003)

kim kardashian butt or brittney spears butt?

Re:For the Americans (1)

thunderclap (972782) | about 2 months ago | (#47086049)

kim kardashian butt or brittney spears butt?

Kim's is far bigger.

Re:For the Americans (3, Funny)

rubycodez (864176) | about 2 months ago | (#47084747)

how many Canadian Imperial Fuckloads is that?

even our hearts are smaller now (-1)

Anonymous Coward | about 2 months ago | (#47083767)

figuratively typing,, millions marching daily (way too many under live fire) (r)evolutionary connection world wide resistance to the never ending WMD on credit book of death & debt zionic corepirate nazi holycost with orchestrated violence including genocidal wmd on credit cabals http://www.youtube.com/results?search_query=wmd+weather no mom is an island but they are our spiritual centerpeace & direct connection with creation in it's most advanced form thus far

Heh (1)

Anonymous Coward | about 2 months ago | (#47083789)

The same thing happens to me every time I eat Chipotle.

"New" volcanos? (5, Interesting)

Immerman (2627577) | about 2 months ago | (#47083799)

So in exactly what sense are these "new" volcanoes not just new vents in the old volcano? Seems to me if they weren't using the old magma channels they wouldn't have opened near the top of an existing volcano - instead they would have opened someplace around the base (underwater) instead. Perhaps more to the point - in exactly what sense is an old volcano which is still spewing lava from it's slopes extinct?

As I understand it it's not exactly uncommon for a volcano to go dormant for a while and then sprout new calderas on it's slopes when it gets active again, particularly if a magma "cork" formed in the old caldera, or the old magma channels collapsed while it was dormant. Seems to me the actual summary should be something along the lines of "what was long thought to be two volcanoes forming Oahu has been discovered to actually be a pair of relatively recent new calderas on a single older, larger volcano."

Re:"New" volcanos? (0)

Anonymous Coward | about 2 months ago | (#47083833)

So in exactly what sense are these "new" volcanoes not just new vents in the old volcano? Seems to me if they weren't using the old magma channels they wouldn't have opened near the top of an existing volcano - instead they would have opened someplace around the base (underwater) instead. Perhaps more to the point - in exactly what sense is an old volcano which is still spewing lava from it's slopes extinct?

As I understand it it's not exactly uncommon for a volcano to go dormant for a while and then sprout new calderas on it's slopes when it gets active again, particularly if a magma "cork" formed in the old caldera, or the old magma channels collapsed while it was dormant. Seems to me the actual summary should be something along the lines of "what was long thought to be two volcanoes forming Oahu has been discovered to actually be a pair of relatively recent new calderas on a single older, larger volcano."

I'd think so, too. But at least it seems to be consistent to this non-volcanologist. Kilauea is considered to be a separate volcano from Mauna Loa also.

Re:"New" volcanos? (5, Informative)

riverat1 (1048260) | about 2 months ago | (#47084133)

In the case of the Hawaiian Islands they form a chain of islands over a hot spot in the Earth's mantle. You can trace the path of the sea floor over the hot spot by following it island arc. So the original volcano formed and as the position of the hot spot moved southeast the volcanoes that comprise the present day Oahu formed on its flanks. The same thing is presently happening on the Big Island, Hawaii where the current volcanic activity is mostly on the southeast at Kilauea and 22 miles out to sea at Loihi Seamount [wikipedia.org] while the northwest part of the island is eroding away.

So obviously the hot spot is forming new magma channels as the sea floor moves over it and whether any particular vent on the flanks of a volcano is a breakout from old channels or a new one is a moot point. Any specific channel won't last for long (in geological time) as the hot spot moves on.

Re: (1)

Anonymous Coward | about 2 months ago | (#47085553)

I believe the hotspot is stationary. The sea floor, the Pacific Plate, is moving in a north westerly direction over the Asthenosphere, which is why you have 5 volcanoes on the Big Island with it's most active, Kilauea, at it's Southern end. BTW, Mauna Loa is still an active volcano, and the very active Loihi seamount is around 3000 feet below the surface of the ocean, as the Big Island creeps Northwest. The area around the oldest volcano in the North of the Big Island, Kohala, is shearing off and slowly sinking back into the sea. I come from North Kohala. Scientists very recently discovered that Oahu was a much bigger island and that it's most westerly volcano, Kaena, had submerged back into the sea after 'briefly' rising from the sea floor.

It walked uphill to school both ways, too (-1)

Anonymous Coward | about 2 months ago | (#47083805)

Now get off of my lawn!

I'm confused (-1)

Anonymous Coward | about 2 months ago | (#47083829)

How do we blame global warming?

The headline made me lol (4, Interesting)

Anonymous Coward | about 2 months ago | (#47083847)

Of course it used to be larger. Hawaii is growing, all the rest of the islands are shrinking (because they are no longer growing).

I knew a marine geologist in Honolulu when I lived out there who was trying to predict the size of the tsunami that would result the next time a huge chunk of Oahu breaks off and falls into the sea. Apparently some pretty large chunks have fallen off in the past.

Re:The headline made me lol (4, Informative)

HiThere (15173) | about 2 months ago | (#47083909)

Bingo!

This is the correct answer. The Hawaian islands form over a "hot spot" under the sea floor that doesn't move with the plate. When the plate moves enough, a new volcanic vent appears. The entire chain of islands is the result of this process. Note that Hawaii, "The big island" is currently over the hot spot, and all the other islands are no longer active. The further away (in a line!) from the hot spot they are, they more they've eroded, so the smaller they are.

Re:The headline made me lol (0)

MildlyTangy (3408549) | about 2 months ago | (#47085413)

Bingo!

This is the correct answer. The Hawaian islands form over a "hot spot" under the sea floor that doesn't move with the plate. When the plate moves enough, a new volcanic vent appears. The entire chain of islands is the result of this process. Note that Hawaii, "The big island" is currently over the hot spot, and all the other islands are no longer active. The further away (in a line!) from the hot spot they are, they more they've eroded, so the smaller they are.

That looks suspiciously like compelling evidence for a >10000 year old earth.

Damn the devil is good! Hes obviously put alot of effort in to making the physical evidence as logical and consistent as possible.

Come to think of it, he would make a damn good engineer if he wasn't so evil. Its a real pity God lets this veritable mountain of evidence against a literal bible slide.

To be honest, He needs to lift His game a bit and put a stop to all this physical evidence thats fooling so so many intelligent humans...the plausible deniability argument is going to be pretty hard for Peter to refute at the Pearly Gates to be honest.

**Before the hate machine begins its inexorable slide over me, please note that this post is actually satire.

Re:The headline made me lol (1)

thunderclap (972782) | about 2 months ago | (#47086065)

Bingo!

This is the correct answer. The Hawaian islands form over a "hot spot" under the sea floor that doesn't move with the plate. When the plate moves enough, a new volcanic vent appears. The entire chain of islands is the result of this process. Note that Hawaii, "The big island" is currently over the hot spot, and all the other islands are no longer active. The further away (in a line!) from the hot spot they are, they more they've eroded, so the smaller they are.

That looks suspiciously like compelling evidence for a >10000 year old earth.

Damn the devil is good! Hes obviously put alot of effort in to making the physical evidence as logical and consistent as possible.

Come to think of it, he would make a damn good engineer if he wasn't so evil. Its a real pity God lets this veritable mountain of evidence against a literal bible slide.

To be honest, He needs to lift His game a bit and put a stop to all this physical evidence thats fooling so so many intelligent humans...the plausible deniability argument is going to be pretty hard for Peter to refute at the Pearly Gates to be honest.

**Before the hate machine begins its inexorable slide over me, please note that this post is actually satire.

Ok, I'll bite. according the Christian Bible, Yahweh is omnipotent. By definition ttp://www.merriam-webster.com/dictionary/omnipotent 'having complete or unlimited power' 'having virtually unlimited authority or influence' 'arrant: being notoriously without moderation' This is what amuses with people. Why can't an entity who has all power and authority create a universe with spoken word instanteously just like it is now and then make it look old? Why couldn't he screw with people and simply keep changing the science? This is the whole point. When you interject an all powerful deity into the mix the answer will always be 'I don't know.' Yes, it could be 10k yrs old and look billions simply because he could. So if you want to believe that great. If you want to believe science is right great. Fighting about it is ignorant.

Re:The headline made me lol (0)

Anonymous Coward | about 2 months ago | (#47085611)

Maui still has an active volcano (Haleakal) so it is also possibly growing

Re:The headline made me lol (1)

HiThere (15173) | about a month ago | (#47088553)

Is it related to the hotspot? My understanding was that Hawaii, itself, was in the process of moving off the hotspot.

I guess the only way to check would be with sonar based around seismograph signals, but there MIGHT be some other way. If it's not related to the hotspot, then I think Maui is probably eroding away, but there's still a chamber of magma underneath that hasn't yet emptied. If that's the answer, then the eruptions of the volcano would tend to result in a generalized lowering of the elevation of the rest of the island. (These processes take a few centuries, though. Canada is still lifting up from the removal of the weight of the glaciers after the last ice age.)

Re:The headline made me lol (3, Interesting)

ShanghaiBill (739463) | about 2 months ago | (#47083947)

Hawaii is growing, all the rest of the islands are shrinking.

Lo'ihi [wikipedia.org] is also growing. Although, technically, it isn't an island (yet).

Re:The headline made me lol (0)

Anonymous Coward | about a month ago | (#47087735)

There's a museum in Honolulu that put together a scale model of that catastrophic break-off you mention. You can hit a button & lamely simulate the resulting tsunamis, which were supposedly scifi dramatic -- hundreds of feet high across s the Western coasts of North & South America. If you live in HI, it's worth seeking out. If you can't get out there, picture the giant glacial calvings that have occurred over the last decade. Looks something like that, except rock, not ice. The remains still lay off the coast of O'ahu (btw, can't we at least try to correctly spell the name of the place we're talking about?) in deep water.

Re:The headline made me lol (1)

RockDoctor (15477) | about 2 months ago | (#47113511)

I don't know the count around the Hawaiian islands, but when I was on a volcanology holiday on Tenerife, Islas Canarias, a couple of years ago the count of "sector collapse" scars identified on the seabed around the islands was in the mid-20, and only likely to go up. That points to around one collapse every couple of hundred thousand years.

If I lived on a coastline exposed to that threat, I'd have included it in my considerations over where to move. As it was I just counted storms, global warming and the Storegga slides.

hurry quick! (-1)

Anonymous Coward | about 2 months ago | (#47083857)

Somebody blame it on climate change

Re:hurry quick! (-1)

Anonymous Coward | about 2 months ago | (#47085177)

No, but I will put the blame for your post on mental retardation.

Waterworld (1)

Myria (562655) | about 2 months ago | (#47084195)

I'll probably sound crazy for asking this, or get modded off-topic, but... My understanding is that the scenario in the movie Waterworld can't happen by melting the polar ice caps because there isn't enough water frozen in them to rise enough enough to cover the continents. Goodbye to Florida and similar areas, but most of the continents would remain. (And thanks to global warming, we'll likely see that scenario... >.<)

But it seems to me as though one way in which it could happen is if we greatly expanded our use of geothermal power, to the point that we exhausted the energy driving plate tectonics. (Hopefully most of the leftover heat would escape into space, or we'd really be screwed.) Then the continents would gradually erode until the solid surface of Earth was at an even level, at which point the existing ocean would completely cover Earth.

To use that much geothermal energy seems pretty ridiculous, though. Just some random Myria musings...

Re:Waterworld (1)

RubberDogBone (851604) | about 2 months ago | (#47084367)

We don't currently possess the technology to extract that much energy from tectonics. By the time we do have the ability, if we live that long, we should have easier ways to make energy.

So we should be OK. Well, not US. But 20 or 30 generations from now.

Nice handle btw.

Re:Waterworld (1)

dbIII (701233) | about a month ago | (#47086221)

It's very shallow two dimensional fiction at the level of which most childrens cartoons can't get away with without criticism. It only resonates with us because it we've got a "the flood was thiiis big (arms spread wide)" story from Sumeria in our culture because it was adopted to make a few points in the Bible. Think about it - does the Bible really suggest everyone is descended from Noah or just everyone considered important to the intended readers?

Re:Waterworld (0)

Anonymous Coward | about a month ago | (#47086437)

It was those nasty comets wot did it.

This is news? (3, Insightful)

Drathos (1092) | about 2 months ago | (#47084303)

My first reaction was "Um.. Duh?"

I learned this in middle school, I believe. The Hawaiian Islands are a chain that's formed by the movement of the Pacific Plate across a hot spot. As it passes over, a volcano builds up and builds up, eventually forming an island that keeps growing as long as the vent stays over the hot spot. Eventually, it will move on and start eroding, while another volcano starts up at the ocean floor. All of the Hawaiian Islands except for Hawai'i (The Big Island) are currently shrinking, while Hawai'i is still growing. If you look at charts of the Pacific Ocean's floor, you can see a long chain going all the way to the subduction zone at the Aleutian Trench.

Re:This is news? (0)

Anonymous Coward | about 2 months ago | (#47084517)

Yes, science should not make observations once a theory has been Um..Duh'd. The theory is so obvious and self-evident, any further testing is just a waste of time. We should have faith in our theories instead of wasting money to test them.

Yes it's news (2)

swillden (191260) | about 2 months ago | (#47084531)

The headline is not news. Everyone knows that the islands are all eroding away, except where new material is being added through volcanic action. But the story is about the ancient volcano that predated the volcano that we knew built the island. That's news, just poorly presented, in slashdot editorial tradition.

Bathymetric map of the Hawaiian Islands (4, Informative)

gkndivebum (664421) | about 2 months ago | (#47084443)

http://maps.ngdc.noaa.gov/view... [noaa.gov]

Zoom in on the Hawaiian archipelago; de-selecting multibeam bathymetry surveys and switching the base map to "Shaded Relief (GEBCO_08) will give
you a nice image of what the chain looks like under water. Kaena Pt is the westermost tip of the island of Oahu. Also note that Maui Nui was once a much
larger island, encompassing Maui, Molokai, Lanai and Kahoolawe. Loihi is visible to the the southeast of the island of Hawaii.

Re:Bathymetric map of the Hawaiian Islands (1)

gkndivebum (664421) | about 2 months ago | (#47094663)

Just found another very useful tool from UH SOEST:

http://oos.soest.hawaii.edu/pa... [hawaii.edu]

Stop plate tectonics! (0)

Anonymous Coward | about 2 months ago | (#47084755)

Global topology change.
The horrors!

Erosion: It Happens All The Time Been Know For 2K (0)

Anonymous Coward | about 2 months ago | (#47085359)

No news.

You can use even piss poor Google Maps to get a view of the islands and "Ha Ha" those northwest have smaller area, by eye, then those south.

An amazing fact !

This is why Geology and Geophysics are considered "Hard" science and 'Geography' and 'Climate "Science"' are considered pitiful !

Why ?

Geography and its 'Freddy Krueger' 'Climate "Science"' have no valid theories !

Can Geography or 'Climate "Science"' predict the mass of the Higgs Boson or the shape of the Arctic Ocean in 20 million years ?

Fucking NO !

Geography is a FAIL ! Kill Geography !

Climate "Science" is a FAIL ! Kill Climate "Science" !

Burn Bay Burn Disco Inferno !

Ha ha

Re:Erosion: It Happens All The Time Been Know For (0)

Anonymous Coward | about a month ago | (#47086469)

It's more scientific than denialism.

about time. (1)

AndyKron (937105) | about 2 months ago | (#47085603)

Glad someone finally figured that out, I was getting worried.

I'm fearful... (1)

Boawk (525582) | about 2 months ago | (#47085753)

...that one of the islands will tip over [snopes.com] .

In other news... (0)

Anonymous Coward | about a month ago | (#47087117)

...the earth has changed in the last several million years. Just thought you would like to know.

Huge Landslides! (2)

bbsalem (2784853) | about a month ago | (#47088957)

For years and years the bathametry off the islands was classified. The reason was that our submarines would hide in the oddly rugged land forms of the subsurface. The lay of the sea floor was declassified when it was felt that our enemies had already mapped it. When the data were made available they unleashed a bonanza of geologic investigation for it became clear that there was a very active process taking place. Much of the strange forms around the islands, all of them, are due to very large slumps, where entire sides of volcanos slumped beneath the ocean suddenly, in a day or less.

I remember being at Wyanii on the west, dry leeward, coast of Oahu and seeing hundreds of individual lava flows in the rugged mountain side. Later I learned that one of the huge blocks that subsided from the coast sat right off shore and realized that the landscape could have been created in an instant as the west edge of the pile slipped off into the deep sea to its west. The ocean off the Islands is more than 3,000 feet deep.

On the east coast of the Big Island is a very active volcano that has been putting out floods of low viscosity basalt to its east. There is also a huge gravity fault that has opened up a miles long rift that faces east. One of these days the whole cubic miles of rock could side off to the east into the abyss. I fear that the wave created will destroy everything on the east edge of the Pacific Basin. I have thought that one might look at places on the West Coast of the U.S. for evidence of the mega wave that could result, because it has happened before many times.

Check for New Comments
Slashdot Account

Need an Account?

Forgot your password?

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>
Create a Slashdot Account

Loading...