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1 Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore O CEAN VENT oceanic vent, hydrothermal vent For the complete encyclopedic entry with media resources, visit: An ocean vent sits over a deep fissure in the ocean floor. Ocean vents eject hot, often toxic, fluids and gases into the surrounding seawater. They often mark sites of tectonic activity, and create some of the most hostile habitats on Earth. Ocean vents are a type of hydrothermal vent. Other types of hydrothermal vents include hot springs, geysers, and fumaroles. As their name indicates, all hydrothermal vents are characterized by water (hydro-) and extremely high temperatures (thermal). Tectonic Activity Ocean vents are the product of tectonic activity beneath the ocean floor. Tectonic activity describes the way tectonic plates, giant slabs of Earth s lithosphere, interact with each other. Ocean vents are found in all ocean basins, although they are most abundant around the Pacific Ocean s Ring of Fire, which also includes active earthquake zones, volcanoes, and ocean trenches. Ocean vents are primarily found around mid-ocean ridges and volcanic arcs. At both mid-ocean ridges and back-arc basins, the molten magma of Earth's asthenosphere wells up close to the surface. Mid-ocean ridges form at divergent plate boundaries, where tectonic plates are 1 of 23

2 moving apart from each other. New oceanic crust is formed at mid-ocean ridges. The Mid-Atlantic Ridge, for instance, runs through the entire Atlantic Ocean, separating the North American and Eurasian plates in the north and the South American and African plates in the south. Ocean vents dot the entire underwater mountain range. Volcanic arcs form at convergent plate boundaries, where a dense tectonic plate is falling beneath a less-dense plate in a process called subduction. Oceanic crust is being destroyed in the subduction zones around volcanic arcs. Volcanic arcs may include volcanoes that rise above sea level, such as Japan s Ryuku Islands, while some volcanic arcs are seamounts, or underwater mountains. Ocean vents found around volcanic arcs are located on the overriding (lessdense) tectonic plate. This area is called a back-arc basin. Back-arc basins are formed as the ocean trench created by subduction migrates backward toward the subducting plate in a process called trench rollback. Trench rollback causes the overriding plate to be stretched thin, creating conditions that allow for the formation of ocean vents. Going with the Flow The process that creates ocean vents takes place in three zones: the recharge zone, the reaction zone, and the upflow zone. Recharge Zone Vent fluid in the recharge zone is formed by seawater seeping into cracks in the seafloor. As the seawater is warmed by its proximity to magma, it is stripped of its magnesium. At this point, seawater changes to an acidic vent fluid. As an acid, the vent fluid leeches more metals from surrounding rocks of the oceanic crust. 2 of 23

3 Reaction Zone The acidic vent fluid continues to heat up as it flows and seeps toward the vent s source of heat. The closer magma wells to the fluid, the warmer the fluid becomes and the quicker its chemical reaction time will be. Chemistry and vent outflow are also influenced by the vent fluid s residence time, or the time it spends in the region close to the heat source. Upflow Zone The vent fluid becomes more buoyant in the reaction zone and races back toward the surface. Incoming flows of vent fluid may also push the superheated fluid upward toward the seafloor. Vent fluid has the least amount of time in this upflow zone. The vent fluid s temperature drops slightly as it races away from the vent s heat source. Vent fluid can lose heat in three major ways. First, heat can dissipate into the surrounding rocks. Second, it can mix with cold seawater seeping in from above. Both of these methods involve a transfer of heat (from the vent fluid to either rocks or seawater). This process is called conductive cooling. The third way a vent fluid can lose heat is through decompression. Unlike the interaction of vent fluid with rocks or seawater, decompression does not involve a transfer of heat. The fluid cools through a loss of pressure. (Pressure is higher in the reaction zone, which lies deeper in the Earth.) This process is called adiabatic cooling. Ejection Sites Hydrothermal vents are where the hot, toxic vent fluids from the upflow zone are spewed from oceanic crust into the surrounding seawater. Hydrothermal vents are narrow and well-sealed, and vent fluids exit at high velocity. Upon contact with the cold, dense ocean, the vent fluid precipitates minerals 3 of 23

4 such as sulfates, sulfides, and quartz. These minerals often give ocean vents their characteristic color. Not all vent fluids are violently ejected into seawater from hydrothermal vents, however. Diffuse flows form in areas where vent fluids mix with cold seawater before exiting the seafloor. Diffuse flows usually cover a larger portion of a vent field than narrow hydrothermal vents. Vent fluids exiting through diffuse flows are usually cooler, less toxic (from mixing with seawater), and exit into the ocean more slowly over a larger area. Diffuse flows also lack the telltale smoke of gushing hydrothermal vents. Plumes As vent fluid is ejected into the ocean, it forms a hydrothermal plume. This plume is more buoyant than seawater, and continues to rise. As it rises and expands, the plume constantly mixes with seawater and its chemistry is diluted. Eventually, the plume reaches neutral buoyancy (the point where the pressure inside the plume equals the pressure of the surrounding seawater, and the plume no longer rises or sinks). At neutral buoyancy, the plume and its chemistry are entirely dispersed by ocean currents. Vent Chemistry The chemistry of ocean vents has an enormous impact on the chemistry of the ocean. At mid-ocean ridges, ocean vents help cool new oceanic crust. At volcanic arcs, they contribute to the geology of the seafloor and even underwater mountains. Temperatures at vent fields range from below 50 Celsius (122 Fahrenheit) to more than 400 Celsius (752 Fahrenheit). Some ocean vents are rich in oxygen and oxygen compounds (such as sulfates), while others are anoxic. Some are 4 of 23

5 highly acidic, with a ph as low as 2. Others have a ph as high as 8. The temperature and chemistry of vent fields varies across the ocean, and these factors are influenced by such features as the frequency of volcanic eruptions in the area, the presence and quantity of sediments, the permeability of the seafloor, the composition of rocks in the oceanic crust, the depth of the heat source, the residence time of vent fluids in the reaction zone, and the water-to-rock ratio at the reaction zone. Temperature Ocean vents help cool the Earth s interior. In fact, oceanographers and geologists estimate that ocean vents account for a whopping 10% of total heat loss from Earth s mantle and core. The temperature of vent fluid is always warmer than the surrounding seawater. Seawater at the deepest ocean vents is just above freezing at 2 Celsius (35 Fahrenheit). Energy from the Earth s superheated mantle and core can heat vent fluid to temperatures of more than to 400 Celsius (752 Fahrenheit). Around diffuse flows, the temperature of vent fluids is usually below 50 Celsius (122 Fahrenheit). The temperature of a vent fluid, and the temperature difference between the vent fluid and surrounding seawater, can determine the chemistry of a vent. For instance, most hydrothermal vents eject vent fluids that would boil at ambient temperatures at sea level. However, at great depths and great temperatures, phase separation (the separation of a liquid into two distinct liquids) prevents vent fluids from boiling. Instead, the chemical reaction between seawater and vent fluid forms a high-salinity brine. This chemical reaction is called brine condensation. Chemicals 5 of 23

6 The most characteristic feature of ocean vents is probably the dense particle plumes that inject chemicals into seawater. Vent fluids most often include sulfides and sulfates. Sulfides are negatively charged ions of the mineral sulfur, while sulfates are negatively charged ions of sulfur-oxygen molecules. Sulfides and sulfates exist in a dazzling array at ocean vents: calcium sulfate, strontium sulfate, zinc sulfide, iron sulfide, copper sulfide, iron sulfide, manganese sulfide. These compounds interact with other elements, including hydrogen, helium, potassium, gold, silver, and cadmium. Perhaps most crucially, vent fluids interact with sodium and chloride, forming salt. As ocean vents eject mineral-rich fluids into the ocean, many of these minerals precipitate, or solidify. Tall, thin vent chimneys are made of these precipitated minerals, including copper, iron, zinc, cadmium, silver, and even gold. As long as they continue to eject fluid, the chimneys continue to grow. Some chimneys can grow 30 centimeters (almost 12 inches) a day and reach 20 meters (65 feet) tall. Tall chimneys don t last long, though. The mineral structure is fragile. Powerful undersea currents and pressure often lead to their collapse. Types of Ocean Vents Ocean vents can be classified as black smokers, white smokers, or snowblowers. All these ocean vents form in the same way. Their differences are marked by color, temperature, and chemistry. Black smokers are the largest type of ocean vent, and eject the hottest fluids. Vent fluids spew out of tall chimneys at rates of up to 5 meters per second (16 feet per second). The smoke blown from black smokers is a dense cloud of particles, mostly metals such as iron and copper. The metals in the fluid mix with the oxygen in the seawater to form a black cloud. 6 of 23

7 White smokers generally develop over cooler vents. White smoker fluid is generally more acidic, and chimneys have much higher ratios of minerals such as zinc, cadmium, silver, and gold. Snowblower vents develop around low-temperature diffuse flows, often around lava from underwater volcanoes. Snowblowers earn their nickname by ejecting columns of white, fluffy particles. Unlike the particle plumes of black and white smokers, snowblower particles are not minerals. The ejecta from snowblower vents are made up of billions of tiny, organic microbes. The heat and minerals present in lava interact with seafloor communities of bacteria and archaea, producing flocculent microbial blooms. Ocean Vent Communities Many unique organisms are adapted to life in the harsh environment of an ocean vent. In fact, ocean vents set the current highest temperature possible for life to exist a fiery 121 Celsius (250 Fahrenheit), found on the Endeavor hydrothermal vents on the Juan de Fuca ridge off the coast of Vancouver, British Columbia, Canada. The producers in ocean vent food webs are extremophiles. Extremophiles thrive in chemically extreme conditions that usually discourage life on Earth. Most food webs on Earth, for instance, rely on the sun. Producers near Earth s sunlit surface (such as green plants and phytoplankton) use sunlight, water, and carbon dioxide to manufacture simple sugars and oxygen in a process called photosynthesis. Organisms near an ocean vent do not always have access to sunlight. These organisms depend on a process called chemosynthesis. In chemosynthesis, microbes convert vent fluids such as hydrogen sulfide into energy (simple sugars), water, and sulfur. Sulfur is naturally a yellow, and many bacterial mats 7 of 23

8 have a characteristic golden color as a result. These specialized microbes (mostly bacteria and archaea, single-celled organisms similar to bacteria) live everywhere in the vent community. They live on the vent floor. They live inside chimneys. They even live inside animals like tube worms and mussels. These microbes are the basis of food webs in the ocean vent ecosystem. Tube worms, mussels, and clams use the microbes to produce nutrients. Plankton and shrimp eat the microbes. In turn, predators like crabs, fish, jellies, and octopuses prey on these animals. The deep ocean is often so dark that many creatures do not have functioning eyes. Their bodies are often gelatinous and lightweight, to offset the crushing pressure of the deep. Ocean vents provide an oasis of biological activity on the ocean floor, which is often dominated by abyssal plains. For this reason, ocean vents have one of the highest rates of biomass of any habitat on Earth. Busy, clustered communities of organisms thrive around the vents, while hardy bacterial mats stretch out meters wider. Exploring Ocean Vents In 1977, oceanographers, led by National Geographic Explorer-in-Residence Robert Ballard, were exploring the Galápagos Rift along the mid-ocean ridge in the eastern Pacific. The scientists noticed a series of temperature spikes in their data. They wondered how deep-ocean temperatures could change so drastically over such a short distance from near-freezing to 400 C (750 F). Ballard and his crew quickly sent cameras to the seafloor to investigate the anomaly. What they discovered, of course, were ocean vents. Fascinated by these undersea features, oceanographers used a submersible to study the vents 8 of 23

9 themselves. They were even more fascinated to discover a diverse, thriving community of living organisms. Until this point, all life on Earth was considered to be dependent on sunlight. Today, oceanographers use an array of instruments to study ocean vents. Bathymetric maps of the seafloor and interactive maps of ocean currents help them identify hydrothermal plumes rising through the ocean. Plumes may be identified through their temperature, chemical structure, and even their color. One of the innovative ways to identify and study ocean vents is the tow-yo. A tow-yo is attached to a research vessel and a collection of sophisticated instruments (called a conductivity-temperature-depth package). The tow-yo raises and lowers the instruments just like a yo-yo within a few hundred meters of the water column. This allows oceanographers to determine the shape of the plume and help pinpoint the vent field from which it came. Once a vent field is located, oceanographers use both ROVs and manned vehicles to study ocean vents up-close and personal. In fact Alvin, the sub originally used by Ballard and his team in the 1970s, is still one of the most effective ways scientists investigate the geological, chemical, and biological characteristics of ocean vents. Most vents are far too deep under far too much pressure, with far too many toxic fluids penetrating the water to allow study by divers. These manned and unmanned vehicles collect samples of the seafloor itself, chimneys, bacteria, and even fish. Benefits of Ocean Vents Ocean vents are one of the primary determinants of ocean chemistry. (Other major contributors include runoff from rivers and atmospheric changes in the air.) 9 of 23

10 The ocean s salinity, for example, was not fully understood until ocean vents were discovered in the 1970s. Prior to the discovery, most oceanographers suspected the ocean was salty due to sediments deposited by rivers and streams. Today, we know the ocean is salty because ocean vents eject chemicals directly in the water column. While ocean vents help explain how chemicals such as salt are added to seawater, they can also help explain how chemicals are taken out. For decades, for example, oceanographers could not explain how the concentration of magnesium in the ocean remained constant. Magnesium was being added to seawater from terrestrial sources, but the chemistry of the ocean remained the same. The discovery of ocean vents solved the mystery: Volcanic rocks in the recharge and reaction zones extract magnesium from seawater. The water coming out of the vents has virtually no magnesium in it. While ocean vents contribute to the ocean s chemistry, their profound heat only slightly influences ocean temperatures. The reason is that while vent fluids are super-hot, they are super-cooled by the tons of cold water surrounding them. In fact, beyond a meter (3 feet) of a vent, the water is back to a near-freezing 1.7 Celsius (35 Fahrenheit). Industrial Applications The unusual properties of ocean vents may influence concepts developed by chemical and industrial engineers in a process called biomimicry. Biomimicry is the process of using the natural world as a guide to develop new technologies. Chemosynthetic bacteria, for instance, may influence the way pharmaceutical companies develop antibiotics and enzymes that combat diseases or injuries. Chemosynthetic bacteria, which convert toxic chemicals to harmless substances, may also provide resources to help clean up hazardous waste or toxic spills in the ocean. 10 of 23

11 Finally, biomimicry may guide engineers to develop ways for machinery to better withstand heat, toxicity, or intense pressure. Mining Ocean vents are surrounded by seafloor massive sulfide (SMS) deposits. SMS deposits are minerals that harden as vent fluid interacts with seawater. SMS deposits can be material left over from collapsed chimneys or even chimneys themselves. They contain metals such as copper, iron, zinc, lead, silver, and gold. These metals are valuable for human industry and can be sold for high prices. Mining companies have studied ways to extract SMS deposits from the deep ocean. Seafloor mining is a complicated and expensive procedure. The environmental impact is enormous. Microbes and animals are destroyed or displaced as the seafloor is disrupted. The waters surrounding Papua New Guinea in the South Pacific are rich in SMS deposits. The world s first major SMS mining operation is expected to begin extraction in this area by Vocabulary Term abundant adjectivein large amounts. abyssal plain extensive, featureless region of the deep ocean floor. acid chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have ph levels lower than 7. adapt verb to adjust to new surroundings or a new situation. 11 of 23

12 adiabatic having to do with a process or chemical reaction that adjective occurs without the gain or loss of heat. air layer of gases surrounding Earth. Alvin ambient anhydrite (1964-present) deep-sea research submersible owned by the U.S. Navy and operated by the Woods Hole Oceanographic Institution. adjectivehaving to do with the surrounding area or environment. (CaSO ) grey-white mineral found in sedimentary rocks. Also known as anhydrous calcium sulfate. anomaly unusual occurrence or abnormality. anoxic antibiotic archaea Term adjectiveno oxygen in the environment. plural substance that can stop or slow the growth of certain microbes, such as bacteria. Antibiotics do not stop viruses. (singular: archaeon) a group of tiny organisms often living in extreme environments, such as ocean vents and salt lakes. array large group. asthenosphere atmosphere back-arc basin bacteria plural layer in Earth's mantle between the lithosphere (above) and the upper mantle (below). layers of gases surrounding a planet or other celestial body. 4 depression on the ocean floor formed as an ocean trench created by subduction migrates backward toward the overriding plate. (singular: bacterium) single-celled organisms found in every ecosystem on Earth. 12 of 23

13 Term bacterial mat collection of microorganisms in which cells adhere to each other or to a surface. Also called a microbial mat, biofilm, or slime (although distinct from actual slime molds). bathymetric representation of spatial information displaying depth map underwater. biological adjectivehaving to do with the study of life and living organisms. biomass living organisms, and the energy contained within them. biomimicry process of using models, systems, and elements of nature as a guide for developing new technology. black smoker type of ocean vent that ejects black mineral fluid (not smoke) into the surrounding water. boil verb to change from a liquid to a gaseous state. brine water saturated with salt. Brine also refers to oceans and seas, and their water. brine chemical reaction between seawater and vent fluid condensation that forms a high-solidity brine. buoyant adjectivecapable of floating. characteristic physical, cultural, or psychological feature of an organism, place, or object. chemical process that involves a change in atoms, ions, or reaction molecules of the substances (reagents) involved. process by which some microbes turn carbon dioxide chemosynthesis and water into carbohydrates using energy obtained from inorganic chemical reactions. chimney tall structure composed of minerals ejected from vents along the ocean floor. cluster verb to gather together in small groups based on certain characteristics. 13 of 23

14 collapse verb to fall apart completely. complicate verb to make more complex, difficult, or detailed. concentration concept idea. conductive convergent plate boundary measure of the amount of a substance or grouping in a specific place. adjectiveable to transmit something, such as electricity or heat. area where two or more tectonic plates bump into each other. Also called a collision zone. convert verb to change or to be changed. convert verb to change or to be changed. core the extremely hot center of Earth, another planet, or a star. crew workers or employees on a boat or ship. crucial data dazzling adjectivevery important. plural decompression dense Term (singular: datum) information collected during a scientific study. adjectiveamazing or extremely impressive. gradual reduction in atmospheric pressure. having parts or molecules that are packed closely adjective together. destroy verb to ruin or make useless. determinant influencing agent or factor. determine verb to decide. diffuse flow an area of the sea floor that forms due to a lowtemperature, slow-moving ocean vent. dilute verb to weaken or reduce. discourage verb to disapprove or encourage someone not to do something. disperse verb to scatter or spread out widely. displace verb to remove or force to evacuate. 14 of 23

15 Term disrupt verb to interrupt. dissipate verb to scatter and disappear. area where two or more tectonic plates are moving divergent away from each other. Also called an extensional boundary boundary. diverse adjectivevaried or having many different types. dominate verb to overpower or control. drastic adjectivesevere or extreme. earthquake the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity. ecosystem community and interactions of living and nonliving things in an area. effective adjectiveuseful or able to perform a task. eject verb to get rid of or throw out. ejecta material ejected from a crater, usually by an erupting volcano or meteorite impact. engineer person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer). enormous adjectivevery large. environment conditions that surround and influence an organism or community. environmental incident or activity's total effect on the surrounding impact environment. enzyme proteins produced in living cells that act as catalysts to accelerate the vital processes of an organism. estimate verb to guess based on knowledge of the situation or object. expensive adjectivevery costly. 15 of 23

16 Term pre-eminent explorers and scientists collaborating with the National Geographic Society to make Explorer-in groundbreaking discoveries that generate critical Residence scientific information, conservation-related initiatives and compelling stories. extract verb to pull out. extremophile microbe that is adapted to survive in very harsh environments, such as freezing or boiling water. fascinate verb to cause an interest in. fissure narrow opening or crack. flocculent adjectivehaving fluffy, cloud-like, soft particles. fluid material that is able to flow and change shape. food web all related food chains in an ecosystem. Also called a food cycle. fragile delicate or easily broken. frequency rate of occurrence, or the number of things happening in a specific area over specific time period. fumarole vent from which steam is emitted. function verb to work or work correctly. gas state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion. gelatinous adjectiveresembling or behaving like a jelly, gel, or gelatin. geology study of the physical history of the Earth, its composition, its structure, and the processes that form and change it. geyser natural hot spring that sometimes erupts with water or steam. gush verb to flow suddenly and forcefully. 16 of 23

17 Term habitat environment where an organism lives throughout the year or for shorter periods of time. hardy adjectivestrong or able to withstand severe weather. hazardous manufacturing byproduct that is toxic or harmful to waste people and the environment. hostile adjectiveconfrontational or unfriendly. hot spring small flow of water flowing naturally from an underground water source heated by hot or molten rock. hydrothermal plume vent fluid ejected into the ocean. hydrothermal opening on the seafloor that emits hot, mineral-rich vent solutions. identify verb to recognize or establish the identity of something. impact meaning or effect. indicate verb to display or show. industry activity that produces goods and services. influence force that effects the actions, behavior, or policies of others. inject verb to force something (usually a liquid) into a cavity or tissue. innovate verb to invent or introduce something new. innovative adjectivenew, advanced, or original. instrument tool. investigate verb to study or examine in order to learn a series of facts. ion electrically charged atom or group of atoms, formed by the atom having gained or lost an electron. lava molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface. leech carnivorous or bloodsucking worm. 17 of 23

18 Term lithosphere outer, solid portion of the Earth. Also called the geosphere. machinery mechanical appliances or tools used in manufacturing. magma molten, or partially melted, rock beneath the Earth's surface. magnesium chemical element with the symbol Mg. manned adjectivecarrying one or more people. mantle middle layer of the Earth, made of mostly solid rock. metal category of elements that are usually solid and shiny at room temperature. microbe tiny organism, usually a bacterium. mid-ocean ridge underwater mountain range. migrate verb to move from one place or activity to another. mineral nutrient needed to help cells, organs, and tissues to function. mining process of extracting ore from the Earth. molecule smallest physical unit of a substance, consisting of two or more atoms linked together. molten adjectivesolid material turned to liquid by heat. neutral condition in which an object's density is equal to that of buoyancy the fluid in which it is emerged. substance an organism needs for energy, growth, and nutrient life. oasis area made fertile by a source of fresh water in an otherwise arid region. ocean basin depression in the Earth's surface located entirely beneath the ocean. ocean current continuous, predictable, directional movement of seawater. oceanic crust thin layer of the Earth that sits beneath ocean basins. 18 of 23

19 Term oceanographer person who studies the ocean. ocean trench a long, deep depression in the ocean floor. ocean vent underwater fissure from which geothermally heated fluid is ejected. ocean vent underwater fissure from which geothermally heated fluid is ejected. organic adjectivecomposed of living or once-living material. organism living or once-living thing. particle small piece of material. permeability measure of a substance's ability to have a another substance penetrate or diffuse it. ph measure of a substance's acid or basic composition. Distilled water is neutral, a 7 on the ph scale. Acids are below 7, and bases are above. pharmaceutical drug or having to do with drugs and medications. phase separation separation of a single solution into two distinct liquids. photosynthesis process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars. phytoplankton microscopic organism that lives in the ocean and can convert light energy to chemical energy through photosynthesis. precipitate verb to separate a solid from a solution. predator animal that hunts other animals for food. pressure force pressed on an object by another object or condition, such as gravity. prey verb to target, victimize, or devour. prior adjectivebefore or ahead of. producer organism on the food chain that can produce its own energy and nutrients. Also called an autotroph. 19 of 23

20 Term proximity nearness. quartz common type of mineral. ratio relationship between numbers or numerical values. Reaction Zone phase in the ocean vent process where the vent fluid is closest to its source of heat. Recharge Zone phase in the ocean vent process in which seawater seeps into fissures in the ocean floor. research vessel ship or boat equipped to carry out scientific experiments or collect data. residence time amount of time a water molecule spends in one place in the water cycle. Ring of Fire horseshoe-shaped string of volcanoes and earthquake sites around edges of the Pacific Ocean. river large stream of flowing fresh water. ROV remotely operated vehicle. runoff overflow of fluid from a farm or industrial factory. salinity saltiness. salt (sodium chloride, NaCl) crystalline mineral often used as a seasoning or preservative for food. seafloor minerals that form from underwater hydrothermal massive sulfide vents. (SMS) deposit base level for measuring elevations. Sea level is sea level determined by measurements taken over a 19-year cycle. seamount underwater mountain. sediment solid material transported and deposited by water, ice, and wind. seep verb to slowly flow through a border. 20 of 23

21 Term snowblower low-temperature ocean vent in which flocculent microbes are ejected. snowblower low-temperature ocean vent in which flocculent microbes are ejected. sophisticated adjectiveknowledgeable or complex. specialize verb to study, work, or take an interest in one area of a larger field of ideas. spew verb to eject or discharge violently. spike verb to increase quickly. subduction process of one tectonic plate melting, sliding, or falling beneath another. submersible small submarine used for research and exploration. sulfate sulfide (SO molecule ) negatively charged ion (salt) of a sulfur-oxygen (S ) negatively charged ion of sulfur, or a chemical compound containing such an ion. sulfur chemical element with the symbol S. suspect verb to assume or believe something. tectonic movement of tectonic plates resulting in geologic activity activity such as volcanic eruptions and earthquakes. massive slab of solid rock made up of Earth's tectonic plate lithosphere (crust and upper mantle). Also called lithospheric plate. temperature degree of hotness or coldness measured by a thermometer with a numerical scale. terrestrial adjectivehaving to do with the Earth or dry land. thrive verb to develop and be successful. 21 of 23

22 Term tow-yo machinery that tows a complex set of instruments (the Conductivity-Temperature-Depth package) behind a research vessel, constantly raising and lowering the CTD to allow oceanographers to determine the shape of a hydrothermal plume. toxic adjectivepoisonous. subduction process in which the leading edge of a trench rollback subducting plate is "rolled back" toward the subducting plate. Also called hinge migration, hinge retreat, or hinge rollback. unique adjectiveone of a kind. Upflow Zone phase in the ocean vent process in which super-heated vent fluid gushes upward toward the seafloor. valuable adjectiveworth a considerable amount of money or esteem. velocity measurement of the rate and direction of change in the position of an object. vent field collection of related hydrothermal vents. vent fluid chemicals ejected by hydrothermal vents. volcanic arc chain of volcanoes formed at a subduction zone. volcano an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions. water column area reaching from the sediment of a body of water to its surface. well up verb to swell or build up. white smoker type of ocean vent that ejects white mineral fluid into the surrounding water. Articles & Profiles Woods Hole Oceanographic Institution: Oceanus magazine How to Build a Black Smoker Chimney 22 of 23

23 National Geographic Magazine: Dawn in the Deep The Bizarre World of Hydrothermal Vents National Geographic News: Heat-Loving Microbes Offer Clues to Life's Origins Pacific Marine Environmental Laboratory: Vent Fluid Chemistry Images National Geographic Education: Marine Communities Instructional Content American Museum of Natural History: Deep Sea Vents NOAA: Ocean Explorer Education National Geographic Education: Hydrothermal Vent Chemistry and Life Interactives NOAA: Ocean Explorer Chemosynthetic Food Web American Museum of Natural History: How Deep is Deep? American Museum of Natural History: Find a Vent Video MBARI: YouTube Channel NOAA: Ocean Explorer YouTube Channel National Geographic Education: Deep Sea Hydrothermal Vents Websites Pacific Marine Environmental Laboratory: New Millennium Observatory (NeMO) National Geographic Society. All rights reserved. 23 of 23