Official Luthiers Forum!

Colin (or anybody else who might know),
Most geological activity happens at the borders between plates. However, I've noticed that there seems to be something going on in the center of plates. For exampmle, Hawaii is in the middle of the Pacific plate and it quite active. The New Madrid fault in the center of the North American plate can generate magnatude 8 earth quakes.

Is this just a coincidence at these two places or is there some geological effect that occurs in the middle of plates.

Mike Mahar38531.5874305556

discuss plate tectonic thoery and how it works. Given that,
I would hypothesise that besides the edges of the plates moving either under ( forming trenches, equal to (forming mountains), or above each other (another trench situation), and these things normally causes the BIG things we hear about in the news, these larger plates themselves are made up of many hundreds to thousands of smaller plate pieces moving together as a while, or at times independantly depending on other acting forces. This would cause local geological activity in seperate regions, not requiring the large magnitude activities as the plate acts as a whole. There are many faults and fissures all along plates, not just at thier boundaries.

Anyone have more info? Or would like to correct mine?
Craig L.

_________________
www.handcraftinlay.com

Well!!! This will help my lutherie

Just Kidding

The Hawwiian Island chain seems to be te result of a 'hot spot': a local upwelling of magma that has remained in the same place as the plates have moved over it. The islands are all in a line, with the oldest at one end and the youngest, and most geologically active, at the other.

The New Madrid fault may be either a sutured and innactive ancient one, or a failed rift. I read something about it once, but that was a long time ago....

Rifts do open up in plates, splitting them in two. The 'Great Rift Valley' in East Africa is such a place. The continental plate becomes thicker as it ages, and provides more insullation. Eventually the heat from the core material beneath works its way up, and starts to melt the underside of the plate, which bulges upward as it gets thinner, until it fractures. Then it subsides, to form a valley, and maybe even an ocean, such as the Atlantic. At least, that's how I remember it.   

"Well!!! This will help my lutherie"


Hey Michael.. Don't you for a moment think this doesn't relate to inlay....
If all of the pieces don't fit together properly it will be a mess. Then if those pieces shift you have major problems.. especially after it's installed    
Add in some heat from underneath, and yes those pieces will shift!
Quick somebody tell Wegener!

C.Lavin

_________________
www.handcraftinlay.com

[QUOTE=clavin] "Well!!! This will help my lutherie"


Hey Michael.. Don't you for a moment think this doesn't relate to inlay....
If all of the pieces don't fit together properly it will be a mess. Then if those pieces shift you have major problems.. especially after it's installed    
Add in some heat from underneath, and yes those pieces will shift!
Quick somebody tell Wegener!

C.Lavin



[/QUOTE]

I am forever ruined by Al Carruth's Chaldni teachings...when I heard plate movement my mind made the leap to think that if we can just get a big enough size glitter and sprinkle it around the pacific rim or other plates that we could find out what frequency the plate is resonating at and could tune it...

Well Mike asked so I better answer although Alan's just about there with his answer.

The Earth's tectonic plates are all in motion at varying speeds and in different directions driven by convection currents in the mantle underlying them and by the gravitational pull of the plates at subduction zones.



Most volcanism and seismic activity takes place at the margins of these plates. However there are points dotted all over the earth where hot magma rises from deeper within the mantle (through processes that would take too long to explain) in the centre of plates, and as Alan correctly said, are called, not overly imaginatively, "Hot Spots". One such hot spot underlies the Hawaii. As the plate moves over the static hot spot one volcano, becomes extinct and a new one is formed.
   

The resulting chain of extinct and active volcanoes is useful in determining speed and direction of plate motion. and the Hawaiian chain shows that the pacific plate has changed direction.



As to the New Madrid fault system, this is the most active fault system East of the Rockies in continental USA, it is part of the Reelfoot Rift, a very early indication that this is a point where a new ocean rift may eventually form. Similar to the opening of the Red Sea or indeed closer to my own home the failed ocean that is now the North Sea. It may also be the point of an earlier continental suture, where old oceans closed, as these form natural weak points for reopening.

The continents that we see now are only transient in nature and have broken up and reformed in different configurations many, many times. USA is itself formed from at least a couple of dozen older micro-continents that have collided and stuck together, and will probably break up again in the future.

By the way Paul Austalia is due to impact SE Asia in about 60 Million years, and Mattia, Italy is due to be crushed out of existance and become the new "Himalayas" as Africa moves north. Sorry about that!

Colin

Colin S38532.2315625

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Thats so cool....
look out Iceland, looks like your splitting in two!

better visit there soon.

[QUOTE=Colin S]

By the way Paul Austalia is due to impact SE Asia in about 60 Million years, and Mattia, Italy is due to be crushed out of existance and become the new "Himalayas" as Africa moves north. Sorry about that!

[/QUOTE]

Good news! They get a lot more rainfall in SE Asia, so I guess this means that the end of the drought is in sight! Worst drought since records began, and only 60 million more years to go! Perhaps a little further off than we were hoping But we'll take it!

Thanks Colin, (and Al, et al) Sorry to go so Off topic but I've often wondered about this and since there was an expert handy I thought I'd ask.

Here in New Hampshire we are part of a land mass that was once connected to some place in Africa. Just across the river into Vermont, the rocks change from Granite to some other brown rock (Basalt?)