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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."
If you head west from Silicon Valley, you'll cross the Santa Cruz Mountains. From these mountains, on a clear day you have a spectacular view all the way across Monterey Bay, to Monterey and beyond.
I mention this because this view of Monterey Bay allows one to easily put things in perspective on how small the habitable life zone on Earth is.
The Bay forms a half-circle, and it's about 30 miles from the Santa Cruz yacht harbor to the Monterey harbor. So you've got one big half-circle with a diameter of 30 miles.
The Earth's crust averages about 20 miles thick on the continents; to within a few miles in the oceans (similar to where this project is drilling, it appears).
So in otherwords, within one Montery-Bay diameter, you are looking at the limit of the Earth's crust; and there are no known life forms below this region (at least presently).
Now look upwards to the sky. 30 miles is about 160,000 feet. The stratosphere and below contain most of the breathable air on Earth (and actually most of it is contained far below this). The well known Ozone layer is at the top of the stratosphere.
The point is, within one Monterey-Bay distance up, you have the limit of the known Biosphere of Earth. Indeed, either one or two diameters is the beginning of Outer Space (depending upon who's definition you use).
And, within one Montery-Bay distance down, you have the limit of the Earth's solid rock. And these distances represent the limits of our Biosphere as we know it.
Consider that well the next time you see pollution going into the atmosphere.
The other reason why this distance is interesting is because you could once could hold the entire Earth's population within it. And perhaps you still can, if everyone squeezes into a 1 square foot area.
The area of Montery bay is 1/2*PI*r^2. With r=15 miles, that's 79,200 feet. So the total area is about 9,848,044,800 square feet.
If you assume 1 square foot per person, the current population can fit within there. Yes, perhaps that's a squeeze, but it does illustrate the point.
So, if you happen to go to Santa Cruz sometime, or some other place where you can see 30 miles away, keep these facts in mind, and it will help give you an idea of how limited our Biosphere is, and how many people are within it.
It is not unlimited, like many people tend to believe.
Yes, but we're dependent on the Morlocks for all of our technology.