...And is this where we'll reshape the earth?;-) See topic #1 for details...

This would be the place, indeed. I think for the basic shape, we should retain the sphere (no matter how oblate) so we spin fast enough to keep us from flying off into space. Other than that...feel free to move about.

Unless, that is, you want to reshape the entire place, which would mean moving the discussion to Orogeny and Diastrophism down the list.

PLATE BOUNDARIES EARTHQUAKES (COMPARE TO MAP ABOVE)

Just too fantastic, Marcia! Love these maps

You have made my day with your comments. Thanks! It is difficult to be inspired to post goodies I find without any input from readers. I really appreciate it!

What I find fantastic about these maps is I personally know the people who created them - they work at the Hawaii Volcanoes Observatory overlooking the main Caldera of Kilauea Volcano. What a splendid place to work!

nice graphics!

Thanks!

Marcia, the tectonic plates map is just what I had asked you for, thank you!

It took me a while, but as soon as I saw it, I knew I had to post it for you!

big [] and :-)

*happy smile*

This map give some indication of the dynamics involved with crust subduction (as in Taiwan) where the Pacific Plate is being dragged under the Asian Plate: From http://wwwneic.cr.usgs.gov/neis/qed/19991020064658.HTML

On the above map, the yellow line is the plate boundary. each little colored circle represents an earthquake. The deepest ones are on the left and the shallowest ones are on the right. People living there must have rubber dishes and drinking vessels rather than china and glassware!

And if I were them, I'd live in tents!

If I were them...I'd live somewhere else!

Right! If possible...

I know "if wishes were horses, beggars would ride"...but, I wish I could see my graphics...*sigh*

The single best place on the Web for Plate Tectonics made easy to understand: http://earth.usc.edu/~stott/Catalina/platetectonics.html Here's how they think it happened: http://pubs.usgs.gov/publications/text/historical.html

The way it looks now

Great links! So it sounds like no one really knows what actually causes the plates to move? Does anyone know what causes "hot spots" like the one under Hawaii?

About the hot spot first...Nope! We are the only one still in evidence the way the earth is configured right now. There are all sorts of places which will tell you how it operates, but no one seems to know WHY it exists in the first place. There is a subtle current driven by convection and subduction which powers the plates around, but it is not that simple. Some are moving away from and toward others in patterns which do not reflect this simple dynamic. I shall keep up on the literature and let post it as soon as there is a better idea out there.

I like this map. What's a hotspot? Or should I say the hotspot, since you say there's only Hawaii.

Ah, The Hot Spot. Glad you asked. I wondered when this would come up, because there isn't a very good explanation of why we are here! http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonics.html Located in the middle of the Pacific Plate, the volcanoes of the Hawaiian Island chain are among the largest on Earth. The volcanoes stretch 2,500 kilometers across the north Pacific Ocean and become progressively older to the northwest. Formed initially above a relatively stationary "hot spot" in the Earth's interior, each volcano was rafted away from the hot spot as the Pacific Plate moves northwestward at about 9 centimeters per year. The island of Hawaii consists of the youngest volcanoes in the chain and is currently located over the hot spot. From: Tilling, Heliker, and Wright, 1987, Eruptions of Hawaiian Volcanoes: Past, Present, and Future: Department of the Interior/U.S.Geological Survey Publication I know these people and there are no better informed on the subject of Hawaiian volcanoes and the "hot spot" theories: The great majority of the world's earthquakes and active volcanoes occur near the boundaries of the Earth's shifting plates. Why then are the Hawaiian volcanoes located near the middle of the Pacific Plate, more than 2,000 miles from the nearest plate boundary? In 1963, J.Tuzo Wilson, a Canadian geophysicist, provided an ingenious explanation within the framework of plate tectonics by proposing the "Hot Spot" hypothesis. Wilson's hypothesis has come to be accepted widely, because it agrees well with much of the scientific data on the Pacific Ocean in general, and the Hawaiian Islands in particular. According to Wilson, the distinctive linear shape of the Hawaiian-Emperor Chain reflects the progressive movement of the Pacific Plate over a deep immobile hot spot. This hot spot partly melts the region just below the overriding Pacific Plate, producing small, isolated blobs of magma. Less dense than the surrounding solid rock, the magma rises buoyantly through structurally weak zones and ultimately erupts as lava onto the ocean floor to form volcanoes. Over a span of about 70 million years, the combined processes of magma formation, eruption, and continuous movement of the Pacific Plate over the stationary hot spot have left the trail of volcanoes across the ocean floor that we now call the Hawaiian-Emperor Chain. Scientists interpret the sharp bend in the chain, about 2,200 miles northwest of the Big Island, as indicating a change in the direction of plate motion that occurred about 43 million years ago, as suggested by the ages of the volcanoes bracketing the bend. Part of the Big Island, the southeasternmost and youngest island, presently overlies the hot spot and still taps the magma source to feed its two currently active volcanoes, Kilauea and Mauna Loa. The active submarine volcano, Loihi, off the Big Island's south coast, may mark the beginning of the zone of magma formation at the southeastern edge of the hot spot. The other Hawaiian islands have moved northwestward beyond the hot spot, were successively cut off from the sustaining magma source, and are no longer volcanically active. The progressive northwesterly drift of the islands from their point of origin over the hot spot is well shown by the ages of the principal lava flows on the various Hawaiian Islands from northwest (oldest) to southeast (youngest), given in millions of years: Kauai, 5.6 to 3.8; Oahu, 3.4 to 2.2; Molokai, 1.8 to 1.3; Maui, 1.3 to 0.8; and Hawaii, less than 0.7 and still growing. Even on the Big Island alone, the relative ages of its five volcanoes are compatible with the hot-spot theory. Kohala, at the northwestern corner of the island, is the oldest, having ceased eruptive activity about 60,000 years ago. The second oldest is Mauna Kea, which last erupted about 3,000 years ago; next is Hualalai, which has had only one historic eruption (1800-1801), and lastly, both Mauna Loa and Kilauea have been vigorously and repeatedly active in historic times. Beacuase it is growing on the southeastern flank of Mauna Loa, Kilauea is believed to be younger than its huge neighbor. The size of the Hawaiian hot spot is not know precisely, but it presumably is large enough to encompass the currently active volcanoes of Mauna Loa, Kilauea, Loihi, and, possibly, also Hualalai and Haleakala. Some scientists have estimated the Hawaiian hot spot to be about 200 miles across, with much narrower vertical passageways that feed magma to the individual volcanoes.

For a general discussion and great graphics concerning Hot Spots, please see http://pubs.usgs.gov/publications/text/hotspots.html The map below shows Hawaii is far from being the only hot spot on earth. Using the Hawaiian Islands as a model here is the dynamics of a hot spot:

I am still amazed that the eruption I saw in 1988 is still going on today, and actually started in 1983! Which brings me to another question. How are "episodes" of an eruption defined?

An epidsode of an eruption ends when magma ceases to feed the chambers and lava output stops. The oneset of another eruption is preceeded by harmonic tremors as seen in this map made just before the latest episode commenced.

Do you remember the campground whose bathrooms were locked when we were down at Waha'ula where the lava was flowing? Nothing is left of it. In fact, David asked me to hurry down and photograph it before it all disappeared, which I did with some remarkable results and near near-prostration. I photographed and watched as the lava crept over the existing structures, beach, trees, grassy area and into the sea. Incredible experience!

Are some of the older islands (extinct volcanoes) of the Hawaiian chain now submerged? Having eroded back into the Pacific?

Some are merely atolls - rings of coral (the original rim of the caldera uponm which many generations of coral have grown)with water inside (Lagoon) and outside. Midway Island is one such, as are several others to the west of the main inhabited islands. Kure is the last island in the group considered an island though the Hawaiian ridge continues northwest from Kure and heads toward Japan. Actually, there are extinct volcanoes on most islands which fit the definition: The volcano has eroded down past the level of the original magma chamber. Cheryl, did you note the graphics I managed to find in the last two days since I got my place on Spring's new hard drive working?!

Graphics have been duly noted. They look great.

I just found the greatest one of all but it is way too big (1,060 KB)to put here and it would slow down the loading significantly. But, go look at it. Very pretty globe, but they need to work on the rotation. http://www.muohio.edu/tectonics/ATglobe.GIF Thanks for looking at the graphics. I was being a bit snippy with an inside joke on my paleo lad assistant who insisted it was Laurelasia and not Laurasia. Oh well, guess you had to be there...! Check Geo2 where volcanoes are discussed first hand! I live on the world's most active one, actually!

(lab assistant...some day, Marcia...!)

Since I cannot put the one I love on Spring (and those of you looking into it, wait till it all loads before you make any judgments. It takes off wonderfully when fully loaded and is a really wonderful gif.)...I offer our globe as Pangaea

Warren's Theory regarding the Juan de Fuca Plate: I'm gonna make like Casey and make a prediction. If you want to know when the big California quake, and its dropping off into the Pacific, will occur, watch the Juan de Fuca plate around Seattle. This little remnant of an older plate is caught between the Pacific plate and the North American plate. When this little one subsides enough under the Pacific plate, I think the San Andreas will let go. My point was simply that with the NA plate pushing west and the Pacific plate pushing south/southeast, the little Juan de Fuca plate seems to be sitting in between these two giants, almost in a linchpin position. My thought is that the "Big One" in California might just come when the Juan de Fuca plate finally lets go and slips quickly under the Pacific plate, allowing the North American plate to move in quickly to fill the void. And we all know how nature abhors a void. The dynamics of his Theory:

Whew! Only took me three tries because I had renamed the file and not refreshed my ftp list...and tried to post a non-existant file...*sigh*

Interesting theory on the effect the subduction of the Juan de Fuca Plate will have on the San Andreas Fault. I am a bit familiar with one that suggests that California will breaking off from North America from roughly south to north. The evidence for this being the Gulf of California. The theory is that Baja California was once attached to the rest of Mexico, and that the Gulf of California is a rift splitting off a section of land, similar to the workings of the Great Rift in Africa.

Indeed, both rifts are zones of expansion. Subduction makes all the fun, though. The cascades are fed by the molten rock pushed into them as the JdF plate dives under the NA plate. I should repost the Volcanic Islands graphic again. In this case the area on that island is being subducted on the western side and expanded on the eastern side. Each little round colored dot represents an earthquake caused by the expansion and subduction going on there.

Sorry about that...try again (if I could telnet I could see what I did wrong)

When California does seperate from North America, the effect might be something like Vancouver Island.

Yes, could very well be! Have you ever checked the islands in the San Francisco Bay? Some, like Alcatraz Island, are rock of a very different sort from the rest of the terrain. It came from far away and down deep! I'd like to read about this stuff, not experience it, thanks. It's gonna be some temblor!

A rather pretty - though not all that informative - map of the World's Plates: See also http://www.spring.net/yapp-bin/restricted/read/geo/26.3 for the comparison of earthquake incidents and plate boundaries. It is not coincident.

You're absolutely right, it's much better to read about massive geophysical events. RE: The remark about earthquake incidents and plate boundaries, the worst earthquake(s) in US History occurred in near New Madrid, MO in 1812-1813. The bed of the Mississippi River was moved several miles in that area, and that part of the river ran backwards (a whirlpool?) for a few days. I think what that means is the flow was temporarily from south to north. Fortunately, that area was not heavily settled then. The point is Missouri is nowhere near a continental plate boundary.

Yup! Thanks for bringing that up in here. It was discussed off-topic in Geo somewhere with KarenR...probably Geo 7....

Nothing much is happening here in Plate Tectonics, on this board I mean not the Earth. As I type this North America, upon which I sit, is headed west, mostly. Marcia, on your intro to this board you note that as one ocean grows another gets smaller. So it is. The Atlantic which at one is believed to have looked something like the Dead Sea, is now a large expanse of open water. The Meditteranean Sea was once an ocean, now it's a land locked sea. Lastly, the great ancient world girdling ocean Panthalassa is now the Pacific and Indian Oceans. The Pacific is still formidable, being the largest physical feature on the Earth, covering about 1/3 of the surface.

Good points, Cheryl...and I seem to be sitting out here on a comparatively miniscule bit of rock which has poked itself above the surface of the world's greatest ocean (actually, they are all one continuous, are they not?!) The spreading of the mid-Atlantic ridge is expanding that ocean, and the subduction of the Pacific plate is making this vast body of water smaller little by little. Hawaii is being dragged inexorably northwestward over that hotspot. One day we will be a suburb of Tokyo, but it won't be there when we arrive...!

Marcia, great discussion. I like the hotspot theory. And the map on post #27 is another for my collection. If you ever need it ;-)

Thanks, Gi. The beautiful thing about the internet is just when it occurs to me that I need an illustration of whatever I am talking about, someone has just posted exactly what I needed.

OT: The "list of the most recent posts" is working again! I am so excited. Thank you, Master Programmer! :-)

*grin* The Magician has done masterful work this morning. We are all pretty again. I also like the lists of the recent posts though I got used to using my main hotlist.

Oh, I admit I use it to see who's online when I am =)

You do, as well?! *grin*

I sorry. I can't help myself. I have the urge to post a bad pun -- we love the Earth in spite of its faults. What would happen if the Earth's crust were of one solid piece; would volcanoes pop up all over the place?

Since we are cooling down slowly, we could not keep from buckling. Imagine a rigid balloon (yeah...right!) or a basketball, even. Now let the air out. It no longer remains a sphere unless there are uniform wrinkles to take up the slack. That is why there is a zone of melting and refilling for volcanoes. Below that it solidifies and above that it solidifies. Clever, this earth, no?! Love your pun...*appreciative groans*

crust dynamics is my favourite topic :-)) Lithospheric flexure anyone? *grin*

Hi Mike!! E Komo Mai...*grin* (Welcome in Hawaiian) Wow! Got a real fan of our plastic earth. Think of the problems we would have without flexure! Big time rending of the surface fabric...much better in little pieces and bit by bit than one gigantic stress buckling. Especially with the tides caused by the Sun and Moon not just on water, but also causing lithosphere bulging in their direction with great regularity. I am delighted out of all proportion to have you post here. Most honored, too. Thanks! Please return. And, if you find great plate graphics, please feel free to post them or let me know and I'll put them on my space at Spring and I'll post them (more permanent that way.) *Hugs*

Hi Marcia, Lithospheric flexure was my research title...lots of great pics and stuff like that. Also some fat math, just to make it look good :-) I'd read up on the hotspot theory before - smart guy that Wilson. You should look at the work of Tony Watts (Oxford University) http://www.earth.ox.ac.uk/~tony/watts/INDEX.HTM and there's also a more index-like page at http://www.earth.ox.ac.uk/~webmaint/Research/Tectonics.shtml Lots of Watts' pictures turned up in my dissertation :-)

Cool, Mike! Great Name for your researcg title! I had no idea of what course of study your University tour was pertaining. How fortuitous.(Happy me... jumping up and down gently because we have had earthquake swarms lately and I do not want to cause a really big one - all 116 pounds of me...) It is way beyond the realm of propriety to ask you to your research in little bits of wisdom from time to time, but I hope you might help someone who graduated from college just before they began teaching Plate Tectonics as a given rather than a theory...and to help keep me on the straight and narrow as to my statements. If I am wrong, correct me, please!!! Off to check your lovely links...sigh! And, he is good looking, too?! Wow!

Oh yes, about that fat math....that is why I am not a professional Geologist. My son can extrapolate and measure the volume of a magma chamber which is totally invisible. I have no idea how and my mind rebels at any attempt on my part to try to understand it. Bravo, Mike! You da Man!

I closed those teeny tags then scribbled them - better hit the softball field!

OK guys, go look at Mike's URLs and see some really great modelling concerning Lithospheric flexure. (Mike! Those guys are using your title!) Be happy it exists or Mauna Loa's weight would have punched through long ago!

Lithospheric flexure is actually a general term rather than something I can claim to have created :-) My research title of "Numerical Modelling of Lithospheric Flexure at Hawaii" was all mine though...doesn't quite roll of the tongue as well as the former, though *grin* LF is really fun...stick a big mountain on the planet to bend it and then work out how thick the crust is based on the bendiness :-))

Only you do not stick it, do you? You pull it, rather, I think ;-)

i think you push for mountains, actually...

I guess you're right :-)

i think you push for mountains, actually...

oops :-) re-posted

or, as with hawaii, you find a hot bit of the earth and run a plate across it, creating your very own chain of private islands

Mike...When were you in Hawaii? You DO know that I live in Hilo on the slopes of Mauna Loa with Kilauea perking just 30 miles away, did you not? Wow! I am fascinated to know more about your research. My son David is also a Geologist...! Auwe! I did not know... No wonder I put you on my babes list with those Blond Brits which run rampant through my family *grin* Please make yourself at home and feel free to correct my (probably) inumerable errors.

Wish William could join the conversation...

alas I've never made it to Hawaii...my work was purely theoretical. I did have a nice dream about flying over the chain once, though...almost as good as being there :-) I would post my diss. if I had a computer copy of it...unfortunately, Mr. Broken Hard Disk ate the only computerised copy...if I ever have the time/energy I'll put it all into the computer again. Several of the pictures I used you have above - cool! :-)

Pox on Broken Mr Hard Drive. Scan it in sometime when you have nothing more pracitcal to do - or better still, when it is published, may I have a reprint (or do they not do that anymore?! I've been to Britain from Hawaii 3 times. It is only s 20-hour flight over what looks exactly like the neatest 3-D topo globe ever. It is your turn to come over here to see how big Mauna Loa can grow before the thickness of the crust limits it - or does it? Or whatever...!

I don't think that the crust thickness can limit the size can it? Although I suppose the lithosphere underneath the main load can fracture...still I'm not sure this can cause a size limit. Maybe it can...I can't remember off the top of my head...

Since you can extrapolate how thick the crust must be to be able to withstand the pressure of mountains of known mass, is it possible to determine what would happen should the mountain mass become heavier than the flex and thickness of the crust can handle? Conversely, does the crust thicken beneath the mountain as it builds greater and greater mass? Has anyone studied this? Is there geological evidence of what happens when the mountain becomes too heavy for the crust and flex to handle? Just curious since I can see the top of Mauna Loa from my yard...!

Mike, here's one for you! ****************************** Postdoc Position in Leeds ****************************** From: Jurgen Neuberg THE UNIVERSITY OF LEEDS SCHOOL OF EARTH SCIENCES RESEARCH FELLOW IN GEOPHYSICS This NERC-funded postdoctoral position is available immediately for a fixed period of three years. Research is primarily in volcano seismology and will involve numerical simulations of seismic wavefields in magmatic environments. Work will be centered on the analysis of seismic as well as other datasets from Montserrat and the development of computercodes to simulate the time-dependence of magma properties in order to compare the resulting seismic signature with Montserrat data. Applicants should have a PhD and research experience in some of the relevant areas of volcanology and seismology, and scientific programming in a Unix environment. Salary will be on the scale for Research Staff Grade 1A, within the range 15,735-17570 according to qualifications and relevant experience. Informal enquiries may be made to Dr Jurgen Neuberg by email locko@earth.leeds.ac.uk or to Dr Brian Baptie bbap@mail.nmh.ac.uk; tel +44 113 2336769 (J. Neuberg, from May 15) Application forms and further particulars may be obtained from Mr Bob Moorcroft, School of Earth Sciences, The University of Leeds, Leeds LS2 9JT UK, tel +44 113 233 5254, fax +44 113 233 5259, e-mail: earrfm@earth.leeds.ac.uk. Closing date for applications 31 May 2000. The University of Leeds promotes an Equal Opportunities Policy. ------------------------------------------------------------------------ Dr Jurgen Neuberg School of Earth Scienecs The University of Leeds Leeds LS2 9JT, United Kingdom Tel: office +44 113 233 6769 home +44 113 293 9392 Fax: +44 113 233 5259 E-mail: locko@earth.leeds.ac.uk ------------------------------------------------------------------------

Just found you. I am new to Geology, having started a college course last September, being 40, have missed a lot of years. Live in England but have a special interest in Washington State having a friend in Seattle. Hawaii is also on the favorites list having covered its volcanic activity in class. Great site, fabulous maps and discussions. Ian

Welcome and Aloha! Your name is on my Yahoo IM list...we must have spoken before. I am available most days Hawaii (which means you are having breakfast as I am having dinner - we are 11 hours behind you!) I have a friend who teaches at Central Washington and has a PhD in Geology. More volcanic Hawaiian stuff on Geo topic 2. I live about 30 miles from the ongoing eruption.

Thanks for the kind comments about Geo. It will be my memorial or whatever. I live in here and finding interesting things for it is a true labor of love. It is nice to have a more mature man amongst us. Happy Me!

Continents in Collision: Pangea Ultima NASA Science News for October 06, 2000 Creeping more slowly than a human fingernail grows, Earth's massive continents are nonetheless on the move. Geologists say that in 250 million years the Atlantic Ocean could be just a distant memory while Earthlings will be able to walk from North America to Africa. FULL STORY at http://science.nasa.gov/headlines/y2000/ast06oct_1.htm?list89800

Ian, this map's for you: http://nmnhwww.si.edu/gvp/volcano/ WORLD VOLCANISM AND PLATE BOUNDARIES - ONE AND THE SAME