Deep biosphere: a hidden, watery world exists beneath the oceans' floors.Beyond the limits of most of the latest ocean observatories lies yet another frontier: a watery realm below the seafloor. Earlier this year, researchers made the first expedition to study life in this deep biosphere biosphere, irregularly shaped envelope of the earth's air, water, and land encompassing the heights and depths at which living things exist. The biosphere is a closed and self-regulating system (see ecology), sustained by grand-scale cycles of energy and of . They found microbes in cores drilled 420 meters into the seafloor off Peru at depths between 150 and 5,300 meters. These microbes might represent as much as two-thirds of Earth's entire bacterial biomass. Scientists propose that similar life might exist below oceans on other planets and some moons.
Before discovering life in the deep biosphere, marine geologists knew from seismic and drilling observations that the seafloor is porous and filled with seawater seawater
Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. . Geologists also knew that this buried seawater, or subseafloor groundwater, moves heat from beneath the seafloor to the oceans. They wanted to learn how fast this groundwater moves, so they installed meter-wide observatories on top of boreholes drilled into the subseafloor. The boreholes are about 25 centimeters in diameter and 100 to 1,000 m deep. Sensors dangling into the holes continuously record the groundwater pressure and temperature.
The observatories are called circulation obviation ob·vi·ate
tr.v. ob·vi·at·ed, ob·vi·at·ing, ob·vi·ates
To anticipate and dispose of effectively; render unnecessary. See Synonyms at prevent. retrofit kits, or CORKs. Soon after their 1991 debut, the observatories revealed that cooling seawater can move quickly through several kilometers of subseafloor. The scientists reached this conclusion when they measured similar temperatures in rock formations that they had expected to hold different amounts of heat.
"Fluids are whistling around clown in this subseafloor ocean," says Earl E. Davis, a geophysicist at the Geological Survey The term geological survey can be used to describe both the conduct of a survey for geological purposes and an institution holding geological information.
A geological survey of Canada in Sidney, British Columbia Sidney is a town located at the northern end of the Saanich Peninsula, on Vancouver Island in the Canadian province of British Columbia. It has a population of approximately 11,300. .
Researchers were surprised to find that their instruments also recorded far more subtle and transient events, such as the tides above them. "Those [events] actually propagate into the subseafloor, and we can watch those," says Davis. As sea levels or even atmospheric pressures rise and fall, the subseafloor changes shape, he says.
Scientists are also using CORKs to watch what happens to the subseafloor during earthquakes and movements of tectonic plates This is a list of tectonic plates on Earth. Tectonic plates are pieces of the Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (60 miles) thick and consist of two principal types of material: oceanic crust (also called in the seafloor. Because this environment is completely saturated with water, CORK measurements are free from water table fluctuations and precipitation effects that distort borehole bore·hole
A hole that is drilled into the earth, as in exploratory well drilling or in building construction. measurements on land.
"We're able to look at some of the processes--like earthquake rupture processes or strain buildup before, during, and immediately after an earthquake--that can't be [observed] otherwise," explains Davis. He and his colleagues reported these findings in the October 2001 Journal of Geophysical Research Journal of Geophysical Research is a publication of the American Geophysical Union. JGR was formerly titled Terrestrial Magnetism from its founding by the AGU's president Louis A. .
Last month, the ship JOIDES Resolution installed two more CORKS in a seismically active area off Costa Rica--bringing the worldwide total to 19. According to Keir Becker, a geophysicist at the University of Miami This article is about the university in Coral Gables, Florida. For the university in Oxford, Ohio, see Miami University.
The University of Miami (also known as Miami of Florida, UM, or just The U , scientists aboard the ship also retrieved data from the deepest borehole ever instrumented. The hole penetrates 2,111 m into the seafloor beneath 3,500 m of ocean.--C.M.