Seafloor system has been active for ages. (Long-Term Ocean Venting).Analyses of mineral deposits in and around a unique set of hydrothermal vents beneath the Atlantic Ocean Atlantic Ocean [Lat.,=of Atlas], second largest ocean (c.31,800,000 sq mi/82,362,000 sq km; c.36,000,000 sq mi/93,240,000 sq km with marginal seas). Physical Geography
Extent and Seas
suggest that the site's tallest towers of minerals have been growing for at least 30,000 years.
The vent system, dubbed the Lost City because its lofty chimneys of carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone and dolomite, composed of calcite (CaCO3) and the mineral dolomite (CaMg(CO3)2) respectively. can reach the height of an 18-story building, is situated on the side of an undersea mountain about 2,500 kilometers east of Bermuda and 15 km away from the Mid-Atlantic Ridge (SN: 7/14/01, p. 21). The mineral-rich fluids that spew from the ocean floor are warmed by heat-generating chemical reactions between ocean water and subsurface rocks rather than by volcanic activity, a characteristic that sets this vent site apart from all others yet discovered.
The Lost City's formations consist primarily of calcium carbonate calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. , says Gretchen L. Fruh-Green, a geochemist at the Swiss Federal Institute of Technology The Swiss Federal Institute of Technology may refer to one of two institutes of higher education in Switzerland:
The oldest chimney material analyzed by the scientists was deposited about 25,000 years ago, well before the peak of the last ice age. Carbonate deposits in cracks near the vents are about 32,000 years old. Although the team has dated only a few mineral samples, the Lost City vents appear to have been continually active for at least 30,000 years.
White, feathery feath·er·y
1. Covered with or consisting of feathers.
2. Resembling or suggestive of a feather, as in form or lightness.
feath formations that surround the active vents are much younger, deposited only in the past few decades, the researchers report in the July 25 Science.
The hydrothermal hydrothermal, hydrothermic
relating to the temperature effects of water, as in hot baths. activity at the site depends on contact of 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. with freshly exposed rock surfaces, says Fruh-Green. Although tectonic activity in the region probably opened the cracks that initiated the heat-generating chemistry beneath the Lost City, the cracking may persist today because those reactions cause the rocks to swell by up to 40 percent. Fruh-Green and her colleagues estimate there's enough virgin rock beneath the vent system to fuel suburban sprawl around the Lost City for hundreds of thousands of years to come.
These findings could be important for several reasons, says Susan E. Humphris of the Woods Hole (Mass.) Oceanographic Institution. Similar systems may be much more common than scientists have suspected because they've typically confined their search for hydrothermal activity to mid-ocean ridges and the boundaries of tectonic plates. Also, she notes, the analyses could illuminate the role of nonvolcanic hydrothermal systems in the ocean's geochemical cycles, many of which are poorly understood.
Perhaps most intriguing is that the Lost City vent system, which hosts a thriving microbial microbial
pertaining to or emanating from a microbe.
the breakdown of organic material, especially feedstuffs, by microbial organisms. ecosystem, may be the closest analog available to conditions early in Earth's history. Therefore, Humphris says, it's probably the best place to study how evolution first unfolded.