Hole Drilled to Bottom of Earth's Crust

AtariAmarok writes "A new article is up on LiveScience about a hole drilled into the Earth's crust to explore the layers of our planet's substrate. The hole gets closer to the mantle than any other efforts that have gone before. The hole might reach the "Moho" (division between Earth's brittle outer crust and the hotter, softer mantle) within a few years." From the article: "The depth of the Moho varies. This latest effort, which drilled 4,644 feet (1,416 meters) below the ocean seafloor, appears to have been 1,000 feet off to the side of where it needed to be to pierce the Moho, according to one reading of seismic data used to map the crust's varying thickness."

Comments

The More Interesting Story

[Steven Edwards]

Is the link at the bottom which talks about the idea of using a nuke to drop a probe to the earths core.

Re:is it wise?

[perspicaciously]

The pressure inside the balloon is much greater than the pressure outside the balloon

The pressure outside the balloon is the same as the pressure inside the balloon. The reason balloons expand when you fill them with air is so that they equalize the pressures. Since the balloon is made of an elastic material without a rigid structure, maintaining equal pressures on either side of the membrane is the configuration that requires the least energy. As the balloon becomes really inflated, the latex can't stretch easily, and it does compress the air inside--but not much, just 5 or 6 mm of mercury.

when you prick it, the pressure equalizes, causing the balloon to pop

The "pop" isn't really related to the pressure equalizing. The latex is under high hoop and axial stress, and when it gets pricked, the hole that forms breaks lines of stress and the latex gets pulled away from the hole. This tears the latex, very rapidly--considerably faster than the speed of sound. The ends of the latex are under so much stress that they contract as fast as the tears occur, and create a small shockwave/sonic boom. When put scotch tape on the balloon where you prick it (before pricking it, of course), the strain around the hole isn't enough to start the tears, since that also requires tearing the scotch tape (or tearing away from it).

However, you're very right that we can't compare this to the earth, because the crust of the earth certainly isn't under high uniform elastic tension attempting to maintain internal and external pressures.

Doubtful...

[Pyrosophy]

Unless you live in Chile or Argentina. Check out the antipodes map to see where you'd end up.

Sounds from Hell

[Alien54]

This reminds me of the urban legend that makes the rounds about scientists drilling into the earth being startled by the sounds of hell emerging from the pipe. Complete with escaping bat or demon emerging from the pipe.

Click here for info on how this story really came about.

Someone finally did the leg work to track the story down. On the other hand, I would like to find the source of the Audio Clip.

Re:Would it work?

[Kymermosst]

IANQAG (I am not quite a geologist), but I am just finishing up my minor in Geology, and considering it as a second major.

Unlikely. The Mohorovicic (Moho) discontinuity can be described in a few different ways - either where seismic veolocities have a marked discontinuity, or where a noticable chemical/mineralogical change occurs (can't remember what it is, I'm a geophysicist, not a geologist).

Seismic discontinuity.

Anyway, regarding the grandparent... in theory, the only thing keeping the mantle from melting is pressure (phase diagrams are easy to find). When you drill down, if you don't maintain pressure in the well, (again, in theory) you might be able to relieve the pressure on mantle rock and cause it to melt. Of course, you'd need a really big hole for the resulting magma to come up before it plugs itself like a puncture wound.

Making an artificial volcano is a highly unlikely thing to accomplish, either on accident or on purpose.

I've read one theory about the yellowstone hotspot that is related to this. David Alt and Donald Hyndman believe (found in _Roadside Geology of Idaho_) that a meteorite struck the pacific northwest and the impact crater relieved pressure on the mantle, allowing the magma to well up. This, of course, relieved pressure below and caused further upwelling. Each eruption of what is now the Yellowstone hot spot keeps the cycle going, they claim.

I don't think it's a very probable explanation, and it doesn't seem to be easily verifiable or falsifiable, since the original evidence would have been destroyed by the volcanic eruptions.