Mid-ocean ridges and spreading zones are home to hydrothermal vents. Hydrothermal vents in the ocean are analogous to geysers and hot springs on continents where groundwater percolates up to 2 km below the surface to areas that are very hot.
The resulting boiling water and steam rush to the surface. At hydrothermal vents, cool seawater percolates down in fissures and cracks created by the spreading seafloor. Throughout this process, minerals like copper, zinc, iron, and sulfur dissolve in the water. Although the water is very hot, it does not boil due to the high hydrostatic pressure. When the super heated water rises out through the vents because it is buoyant, it meets relatively cold and oxygen rich ocean water and many of the dissolved minerals precipitate out as particles.
If the majority of precipitates are sulfides and have a black color, the vents are known as black smokers due to their dark billowing appearance Fig. White smokers emit minerals with lighter hues Fig. In some cases these particles combine to form chimney structures around the vents Fig. In scientists discovered a field of chimneys in the Atlantic ocean basin that had reached 55 meters tall. Hydrothermal vents are found in spreading regions on the seafloor. One of the most surprising discoveries for scientists, who first looked at photographs of hydrothermal vents, was the highly productive benthic community surrounding them.
Many types of organisms have adapted to live in these extreme habitats. These include crabs, mollusks, and worms Fig. The base of the food web in these communities are microorganisms or microbes that use compounds, particularly hydrogen sulfide and methane, from the vents and convert them to useable energy and food.
In virtually every other ecosystem on Earth, the ultimate source of energy is the sun. Some vent tube worms have adapted so they are entirely dependent on symbiotic microbes that convert hydrogen sulfide and methane into food Fig.
The worm provides a suitable environment and steady supply of nutrients to the microorganisms and the microbes supply the worm with food. Scientists discovered the first hydrothermal vents in at the 2.
These vents were discovered when scientists observed unusual hotspots during a deep water survey. Subsequent dives using submersibles allowed scientists to view hydrothermal vents firsthand.
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Main menu About this Site Table of Contents. The Oceanic Crust and Seafloor. MS-ESS Construct a scientific explanation based on evidence for how the uneven distributions of Earth's mineral, energy, and groundwater resources are the result of past and current geoscience processes.
HS-ESS Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes. The content and activities in this topic will work towards building an understanding of the rock cycle and movement of crustal rocks on Earth.
Weird Science. Further Investigations. Activity: Crayon Rock Cycle. Today, tectonic activity is responsible for the formation and destruction of crustal materials. The transition zone between these two types of crust is sometimes called the Conrad discontinuity. Silicate s mostly compounds made of silicon and oxygen are the most abundant rocks and minerals in both oceanic and continental crust.
Oceanic crust , extending kilometers kilometers beneath the ocean floor, is mostly composed of different types of basalts. Basalts are a sima rocks. Oceanic crust is dense, almost 3 grams per cubic centimeter 1. Oceanic crust is constantly formed at mid-ocean ridge s, where tectonic plate s are tearing apart from each other.
The age and density of oceanic crust increases with distance from mid-ocean ridges. Just as oceanic crust is formed at mid-ocean ridges, it is destroyed in subduction zone s. Subduction is the important geologic process in which a tectonic plate made of dense lithospheric material melts or falls below a plate made of less-dense lithosphere at a convergent plate boundary.
At convergent plate boundaries between continental and oceanic lithosphere, the dense oceanic lithosphere including the crust always subducts beneath the continental.
In the northwestern United States, for example, the oceanic Juan de Fuca plate subducts beneath the continental North American plate. At convergent boundaries between two plates carrying oceanic lithosphere, the denser usually the larger and deeper ocean basin subducts. In the Japan Trench, the dense Pacific plate subducts beneath the less-dense Okhotsk plate. As the lithosphere subducts, it sinks into the mantle, becoming more plastic and ductile.
Largely due to subduction, oceanic crust is much, much younger than continental crust. The oldest existing oceanic crust is in the Ionian Sea, part of the eastern Mediterranean basin. The seafloor of the Ionian Sea is about million years old. The oldest parts of continental crust, on the other hand, are more than 4 billion years old.
Geologists collect samples of oceanic crust through drilling at the ocean floor, using submersible s, and studying ophiolites. Updates on outreach activities, information about how the geosciences interact with society, details of policy related meetings, consultation responses, and policy briefing notes. Geoscientist is the Fellowship magazine of the Geological Society: with news about science, people, the Society, features, reviews, opinion, letters and forthcoming events.
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The Geological Society of London is the UK's national society for geoscience, providing support to over 12, members in the UK and overseas. Founded in , we are the oldest geological society in the world. Q: I have been wondering a few of things over the last few days after being asked a question, and can't find an answer that I find satisfying. They are: If granite is an intrusive igneous rock, how is it that most of the continental crust is made up of it?
I mean, if it was intrusive, what did it all intrude into in the first place? Following on from that: When and how did the first continental crust form? If it was granite, then what did it intrude into in the first place? Did all the continental crust first form in one place as one land mass, and if so why?
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