So that we could understand it?
If I understand it correctly, the crust is tens of miles thick. We have no technology that even comes close to being able to drill that far.
Well, how about just the first few layers just so that we can know about it better?
Using natural earthquakes and the use of seismic surveying are the 2 major ways of determining layers for the first ~ 5 km of crust.
Tho it doesnt specifically tell you what those layers are made of it does tell you about the thickness of each layer, depth below surface and velocity factor of each layer ( from which you can make educated guesses of the type of rock the different layers are)
When i was doing my BSc in geology at Uni, part of the course was learning to interpret seismic surveys
just a little correction... phinds commented on the crust being 10's of miles thick, whilst this is correct for the thickest parts of continental crust, it isnt for oceanic crust which avg's ~ 10km (6 miles) thick. Which is what you originally asked about.
Wikipedia came up with some interesting facts.
the greatest depth drilled so far is ~ 12,289m 12km .... 7.5 miles !! awesome
there appeares to be a number of drill sites around the world that have got between 5 and 12 km
That is somewhat misleading. I believe you are quoting the figures for a Qatar well that reached total depth in 2008. This is an extended reach well, so that the true vertical depth (TVD) is considerably less than the measured depth (MD) - the depth quoted. The horizontal portion of the well is around 10km, so TVD will be not much more than 1km.
The only slightly shorter (12,262 m MD) Kola well remains - to my knowledge - the deepest TVD achieved to date.
Thank you for that correction. I did not realize there was such a significant variation.
You could just walk around on Iceland, where the Mid-Atlantic rift is on the surface !!
Okay, sorry, that's a bit facetious, because you won't get the complex chemical changes due saline hydrothermal circulation etc etc....
IIRC, there's a drill-ship hoping to retrieve gabbro from ~2km depth off Costa Rica this Summer. Borek's post's search parameters have it in the top ten Google hits...
NO, I was quoting the Kola !! :) give or take a few metres, Not familiar with the Qatar one
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