Geologists plan journey to Earth's mantle for 2020
By Duncan Geere, 28 March 11.
Previous attempts to reach the area below the Earth's crust have failed, but that hasn't deterred a team of geologists and oceanographers from planning to have another go in 2020.
The first attempt took place in Spring 1961, and was known as Project Mohole, because the team behind it were trying to drill a hole through the Mohorovičić discontinuity -- the zone between the crust and the mantle. However, after drilling a hole just 180m deep, the project was abandoned due to cost overruns.
Since then, we've repeatedly probed the seabed (where the crust is thinnest) with drills, making it down to 1,416m below the surface in 2005 and 2,100m at the Integrated Ocean Drilling Program's Hole 504B. As the crust is 6-7km thick on average, this represents scant progress.
However, a report in the journal Nature proposes another go, using the Japanese drilling ship Chikyu, which can carry 10km of pipes (however was recently damaged by the Japanese tsunami). Damon Teagle is a co-author of that paper and told BBC News: "This would be a very significant engineering undertaking. We're talking 6km of ocean crust and we'd want to get some distance into the mantle -- maybe 500m. So that's a very deep hole; and it would be in water that is perhaps 3-4km deep as well. Also, we would encounter temperatures around 250-300 degrees at least. It would be hot and demanding."
The technology to get that far down, and the funding necessary to acquire it, isn't expected to arrive until at least 2018, hence the delay in the start of the project. That hasn't stopped the team behind the project scouting out possible locations -- narrowing the choice down to three locations in the Pacific.
The eventual goal is to recover materials from inside the mantle, to try and learn more about the Earth's internal composition. The mantle is thought to primarily be composed of peridotites -- olivine and pyroxene. While samples of these materials have been recovered from volcanoes, they tend to be altered by their journey to the surface. Acquiring unaltered, pristine samples would tell us a lot about convection below the crust, giving us insights into seismology.
"We want, for the first time ever, to sample these kinds of rocks in situ, to test the different models that we have to explain the behaviour of this crust," said Teagle.
Previous attempts to reach the area below the Earth's crust have failed, but that hasn't deterred a team of geologists and oceanographers from planning to have another go in 2020.
Source article @ Wired
Previous attempts to reach the area below the Earth's crust have failed, but that hasn't deterred a team of geologists and oceanographers from planning to have another go in 2020.
The first attempt took place in Spring 1961, and was known as Project Mohole, because the team behind it were trying to drill a hole through the Mohorovičić discontinuity -- the zone between the crust and the mantle. However, after drilling a hole just 180m deep, the project was abandoned due to cost overruns.
Since then, we've repeatedly probed the seabed (where the crust is thinnest) with drills, making it down to 1,416m below the surface in 2005 and 2,100m at the Integrated Ocean Drilling Program's Hole 504B. As the crust is 6-7km thick on average, this represents scant progress.
However, a report in the journal Nature proposes another go, using the Japanese drilling ship Chikyu, which can carry 10km of pipes (however was recently damaged by the Japanese tsunami). Damon Teagle is a co-author of that paper and told BBC News: "This would be a very significant engineering undertaking. We're talking 6km of ocean crust and we'd want to get some distance into the mantle -- maybe 500m. So that's a very deep hole; and it would be in water that is perhaps 3-4km deep as well. Also, we would encounter temperatures around 250-300 degrees at least. It would be hot and demanding."
The technology to get that far down, and the funding necessary to acquire it, isn't expected to arrive until at least 2018, hence the delay in the start of the project. That hasn't stopped the team behind the project scouting out possible locations -- narrowing the choice down to three locations in the Pacific.
The eventual goal is to recover materials from inside the mantle, to try and learn more about the Earth's internal composition. The mantle is thought to primarily be composed of peridotites -- olivine and pyroxene. While samples of these materials have been recovered from volcanoes, they tend to be altered by their journey to the surface. Acquiring unaltered, pristine samples would tell us a lot about convection below the crust, giving us insights into seismology.
"We want, for the first time ever, to sample these kinds of rocks in situ, to test the different models that we have to explain the behaviour of this crust," said Teagle.
Previous attempts to reach the area below the Earth's crust have failed, but that hasn't deterred a team of geologists and oceanographers from planning to have another go in 2020.
Source article @ Wired