You've probably seen or heard of natural hot springs on land, like Old Faithful at Yellowstone National Park. Similar phenomena occur under the oceans within midocean ridge volcanoes and are called deep-sea hydrothermal (hot water) vents. They are known as black smokers, like the ones seen above. These black smokers are chimneylike structures made up of sulfur-bearing minerals or sulfides that come from beneath Earth's crust. They form when hot (roughly 350íC), mineral-rich water flows out onto the ocean floor through the volcanic lava on a mid-ocean ridge volcano.
Sulfide minerals grow or crystallize from the hot water directly onto the volcanic rocks at the place where the hot, mineral-rich water flows from the ground. This crystallization forms a hollow, chimneylike sulfide structure through which the hot water continues to flow. As the hot, mineral-rich water rushes out of this chimney and mixes with the cold ocean bottom water, it precipitates a variety of minerals as tiny particles that make the the vent water appear black in color. This is why these sulfide chimney structures are called black smokers.
Black smokers tend to occur on sulfide mounds (large piles of sulfide minerals built up over time) in vent fields that are typically tens of meters across. The areas of these fields range from pool table size (4 square meters) to tennis court size (770 square meters). Vent fields with towering sulfide chimneys on the Juan de Fuca Ridge (the destination of this expedition) have been compared to Bryce Canyon National Park in Utah. Other vents have been given names based on their appearance, such as Anemone Heaven, Garden of Eden, Snake Pit, Whelks Club, and Beehives.
Deep-sea hydrothermal vents occur along the midocean ridges. Several different vents have been discovered since the first site was found in 1977 near the Galapagos Islands by earth scientists in the small research submersible ALVIN. One reason that relatively few sites have been observed is that scientists have explored only a small portion of the 50,000 kilometers of midocean ridges. So it is likely that as scientists explore more of the midocean ridges they will discover more deep-sea hydrothermal vent sites. In fact, scientists also have found that not every ridge has a deep-sea hydrothermal vent site. Scientists don't know exactly why some ridges have deep-sea hydrothermal vents and others don't. Two areas of active research are exploration of ocean basins and investigation of the processes that cause deep-sea hydrothermal vents. This expedition will make observations and collect samples that scientists will use to learn more about the processes at deep sea hydrothermal vent sites.
Large amounts of heat and chemical mass are transferred from deep within Earth to Earth's surface through deep-sea hydrothermal vents. The chemistry of ocean water is controlled in part by this process. Thus, understanding how deep-sea hydrothermal vents work is critical to understanding the dynamic nature of our planet.
Deep-sea hydrothermal vents support extraordinary ecosystems deep beneath the surface of the oceans. These ecosystems are the only communities on Earth whose immediate energy source is not sunlight. Life on Earth, and even possibly on other planets, may have formed in environments similar to these.
The life-forms that support the food chain at deep-sea hydrothermal vents also participate in the formation of the minerals that make up the sulfide chimney structures. Understanding this biochemical mineral formation process will help us to understand ore (minerals of economic interest) formation processes in general.