题目内容

"Hydrothermal vent" is the term that scientists use to describe a crack in a planet's surface from which geothermally heated water emerges. Because these vents are common in places that are volcanically active, they are plentiful on Earth. While the most famous hydrothermal vent is probably the geyser at Yellowstone National Park in the United States, there are several different types of vents, existing both on land and underwater. Black Smokers, for instance, are a common type of submarine vent. The National Oceanic and Atmospheric Administration first discovered these in the vicinity of the Galapagos Islands in 1977. Underwater vents such as these form when water that has been heated by magma beneath the earth's crust exits through cracks in the ocean floor. Scientists are interested in these vents primarily for their ability to host biologically dense communities in areas that are otherwise hostile to life. Studies show that Chemosynthetic archaea, a life form similar to bacteria, allows these areas to support such diverse organisms as clams and shrimp. Black Smokers are also visually striking. Minerals in the water that emerge from the earth's crust crystallize around each vent to create their distinctive black chimney-like formations.

While on a vessel exploring the Atlantis Massif in the mid-Atlantic Ridge, scientists recently discovered a completely new kind of hydrothermal system, which they dubbed "Lost City." Here, a "forest" of white limestone pillars rises 180 feet above the sea floor. There are several important differences that distinguish the hydrothermal vents in Lost City from the more familiar Black Smokers. The heat and fluid flow at Lost City is driven by the intermingling of seawater and mantle rocks on the sea floor, rather than by hot magma. As these fluids mix with magnesium-rich sea water, they deposit calcium carbonate and magnesium hydroxide, thereby creating the stunning white structures of Lost City. The fluids here are also much cooler (less than 100 degrees Celsius) and are composed of substances and gases that are different from those of Black Smokers. For instance, the fluids here have high pH content and contain significant amounts of hydrogen and methane gas.

The discovery of Lost City is still a fairly recent one. and scientists currently have more questions than answers. However, they hope that the insights they gain from this study will provide information that will lead to a better understanding of some of the earliest hydrothermal systems on earth and the life they supported.