2.5 Mile Deep Hole Drilled Into San Andreas Fault

iandoh writes "Cool research: Geologists at Stanford University and the US Geological Survey have drilled a 2.5 mile deep borehole into the San Andreas fault. They've extracted over one ton of rock from 2 miles down, and they'll be installing sensors down the length of the borehole."

Comments

Re:Only 2.5 miles?

[Harmonious Botch]

A quick google revealed the following:

The deepest oil well penetrates a mere six miles (ten kilometers) into the crust (the center of the Earth is about 4,000 miles [6,000 kilometers] deeper). Russian scientists dug the deepest hole on the planet in Siberia, but bottomed out at about 7.5 miles (12 kilometers) below the surface. The Mohole project, a 1950s-era U.S. plan, called for drilling a hole 25 miles (40 kilometers) down to the Mohorovicic discontinuity, the boundary between the hard rocks of the crust and the gooey mantle. Sadly, the only discontinuity Mohole ever encountered involved government funding.
It gets harder and harder to drill deep into the Earth because rocks get softer and softer. Brittle at the surface, rocks become plastic at depth, and the pressure caused by the weight of the overlaying crust--about 52,800 pounds per square inch (3,700 kilograms per square centimeter) at a depth of ten miles (16 kilometers), says drilling consultant William Maurer--collapses deep wells, making further drilling impossible.