Day 14: The fire that fuels life
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July 12, 2011; 16:00 PDT
July 12, 2011; 23:00 UTC
47 45.677100 N
127 45.682920 W
Yesterday night, Jason was used to collect with push cores. These are just plastic tubes around a foot long and four inches across, the kind that you can buy at any hardware store. The tubes are pushed into the mud on the ocean floor, and when withdrawn they contain a plug of sediment with its original layering and chemistry preserved: a core. Holes have been driven into the push core and then covered with duct tape, so that when the cores are returned to us we can remove the tape and stick probes through the pinholes to get at the thick, sandy mud inside. We can also push the mud out the top with a plunger and chop off slices as it comes out. This is called extruding, and its used to take samples from different depths of the first foot of the ocean floor. The first foot happens to be an important one. We’ll probably start doing all this tonight, after Jason returns, as its still at the bottom, filling bags with water. At present, Jason has been on the bottom for about 20 hours, which is the primary advantage the ROV has over deep-sea vehicles like Alvin.
This seems like a good moment to offer a bit more back story on what kind of world we’re exploring. If you stand on a beach, you’re standing at sea level. The average ocean depth is 4,000 m below you, or 4 km. To put that in perspective, a 5k run is 3.1 miles, so the average depth is 4/5ths of a charity race. The bottom of the ocean isn’t a solid, flat, slab like the bottom of a swimming pool, though. Its a bit more like the ground on land. On land, we drill ground wells to provide water in rural areas. These are just pipes that tap into aquifers. Aquifers contain water in the cracks and nooks within the rock, and even if these are small spaces, its enough to provide water to entire communities, so long as it isn’t drained faster than it refills. Getting back to the ocean, you may have seen pictures of hydrothermal vents, tall spires spewing thousands of gallons of water clouded with black, charred dust. The question is, where is all that water coming from? The answer is, “somewhere else”.
Hydrothermal vents were only discovered in the last thirty years. It was only a few decades earlier that geologists began to widely accept that new crust emerges at seams along the seafloor. Its unfortunate that both of these discoveries are rather abstract, as they are evidence of the beautiful fire and might of the Earth below us. Admittedly, I myself didn’t understand the appeal of geology for quite some time. Like a piece of music, however, it is something banal until you comprehend the scale and power of it. These two regions — vents and spreading centers — are windows into the Earth. Most of the rock we encounter is sedimentary. Its old and battered, weathered by millions of years. The rock that forms the crust is the product of real magma, the blood of the Earth. The crust at geological hotspots is even younger. Its fresh from the interior. Its primal.
This is by no means mere poetry. You see, the deep rock of the Earth has a trait that can be hard to understand. In scientific terms, its more chemically reduced than the surface. How this came to be lies at the center of the great, 4 billion year epic that is the story of the Earth, from formation until now, but what it means is that the rocks contain energy within their molecules. Its a common misconception that the life around hydrothermal vents feeds off of the heat. The heat is important, but it is the energy in the very makeup of the rocks on which the life there relies. I don’t mean to inspire fables about mythical energies in the Earth and rocks, though I confess that such fables might be the only means of doing these stories justice, outside of a lot of very exhaustive study.
This energy is rather weak, really. Its not something that could power your car (though its no coincidence that coal and oil, which can, are found deep underground). There is, however, a lot of it. Like all energy, it is change, or at least the desire to change. These rocks are the positive terminal of a battery, and the negative terminal is the minerals dissolved in seawater. Remarkably, of all the metaphors I’ve employed, this is the truest. In fact, its really not so much a metaphor as a literal truth. Don’t worry though, its not important whether that makes sense.
The overall point is that 2% of the ocean is flowing though invisible rivers deep underground beneath the ocean, where perhaps more than 10% of the life on Earth (by weight) grows. We don’t really know. If we knew more, it would inform our understanding of surface climate, the beginnings of life, and the possibilities of life outside our planet. Unfortunately, its behind a brick wall a mile thick, turned on its side and underneath another 3 miles of salty water. Thats pretty far away. Lucky for us, we’ve got some VERY long drills bits.
