Plate tectonics introduction
Plate TECTONICS
About 2,000 large earthquakes occur every year. The tectonic theory says that the world's tectonic plates are not fixed forever, but constantly changing and in motion. Tectonic forces originate from the mantle of the earth, the hot, thick liquid upon which the earth's crust sits. There are three essential layers of the earth: the core, the mantle, and the crust. Tectonic activity is centralized in the upper 700km of the planet, the uppermost mantle and the crust. The Lithosphere (top 100km) includes the outer mantle and the crust. Below this is the Athenosphere, a hot and squishy part of the earth which the crust and outer mantle "float" on. The Athenosphere is important to plate tectonics because it is what the tectonic plates sit on in order to move around. On average, tectonic plates move at about the same speed at which fingernails grow. There are three kinds of plage boundaries: convergent, divergent, and transform. In divergent boundaries, two plates are being pulled away from each other, and in between them, new mantle flows up and hardens, making new crust. These are mostly located along the ocean floors. Magma that flows up hardens into basalt, making it the material of the Oceanic Crust. At convergent boundaries, two plates are being pushed into each other, colliding. As this happens, one plate folds underneath the other, which melts back into the earth's mantle. This often forms deep sea trenches. As this happens, the top plate releases magma, which hardens and forms granite, the structure of the continents. At transform boundaries, two plates are sliding or grinding next to each other in the opposite direction. These are special because earthquakes are very frequent in these areas.
Lithosphere and athenosphere
The Lithosphere is the uppermost 100km of the earth, and the Athenosphere is the upper 700km.
Convergent boundaries
These boundaries rip away from each other, and can create large rifts or canyons.
Divergent boundaries
These boundaries push against each other, which forces one layer under the other, causing it to melt. As this layer melts, part of it flows back up to the surface, creating the new material for the top layer.
transform boundaries
These boundaries slide against each other, often creating much seismic activity, or earthquakes.
Mid ocean ridges
introduction to mid-ocean ridges
NOAA is the National Oceanographic and Atmospheric Administration, a leader in exploring geological and biological mysteries of the deep sea. The mid-ocean ridge system is a long expanse of plate boundaries, wrapping around the whole world underwater, about 65,000km long. Here, new ocean crust is created, as magma rises up and solidifies. The kind of plate boundary that forms a mid-ocean ridge is a divergent plate boundary (two plates that pull apart). A ridge is where the plate boundary actually meets, and in that place it rises as the magma is being forced up, creating large mountain ranges. New basaltic magma from the athenosphere rises up to create the new oceanic crust. As the new lava emerges, the outermost part of it almost instantly solidifies, while the inside is still liquid, and keeps moving. This creates a "pillow basalt" in which there is a very thin layer of liquidy magma that coats the ridge. At the Juan de Fuca ridge, new crust is being continually made, pushing apart the plates, and enlarging the ocean sea floor slowly but surely. The rate at which spreading takes place dictates the surrounding landscape of the ridge. Quick rates lead to smoother surfaces, while slower rates create jagged mountains and valleys. Water in these areas can reach temperatures of up to 400 degrees Celsius. These ridges have many cracks, which sea water flows into. As the sea water sinks into the cracks, it meets the magma, and superheats, dissolving minerals, and is jetted up to the surface violently, creating thermal vents. This hot water is very important to an ecosystem which survives off of it, as the minerals support it's life cycle and food chain. Chemeosynthesis in the process in which organisms convert minerals into energy. It is different from photosynthesis because photosynthesis uses light energy, whereas chemeosynthesis uses minerals instead, because there is no light at the bottom of the ocean.
pillow basalts
Pillow basalts are where the magma meets the surface. The outer shell hardens, while the inside is still liquid, and it continues to spread.
thermal vents
Thermal vents form when cracks in ridges form. The water seeps into the cracks, becomes superheated from contact with the magma, dissolves minerals, and is violently shot up back to the surface. The minerals then support a chemosynthetic ecosystem that turns the minerals into energy.
hydrothermal vents
"black smokers"
Black Smokers are hydrothermal vents that range from 350 degrees centigrade to 400 degrees centigrade. At this temperature, the water is hot enough to dissolve metals into the stream of hot water, which gives the water from these vents their black color.
water boiling points
As you travel down into the ocean, the boiling point is not the same as it is at the surface. Why? Pressure. At the surface, the pressure is equal to one atmosphere. Down at 2,500 meters, there are 250 atmospheres of pressure on the water, raising the boiling point of the water. (For every 10 meters, the pressure increases by one atmosphere).
vent chemistry
As the hydrothermal vents throw hot water into the ocean, it also changes the ocean's chemistry. As the water gets superheated, it dissolves minerals and metals into the solution, releasing them up into the ocean, which changes it's chemistry entirely.
vents around the world
Hydrothermal vents only occur in places of volcanic activity, where the magma is close enough to the surface to heat the water. They are mostly located along faults and deep sea trenches, however a few are on land, such as in Yellowstone National Park in the US.
animals around hydrothermal vents
Many organisms live around hydrothermal vents. Hydrothermal vents are practically their own ecosystem, with many well-adapted life forms living there. Pictured to the left are tube worms, worms that live in shells made of chitin that use bacteria living inside of them to survive through a symbiotic relationship, where the bacteria turn the minerals into sugars which the worms eat. Other organisms include shrimp, mussels, clams, octopi, deep sea fish, and crabs. Octopi and Zoarcad fish are on the top of the food chain in the vent ecosystem.
chemosynthesis
In chemosynthesis, organisms use minerals in the water to survive. They use the minerals and turn them into energy through chemical reactions, as opposed to plants, which through photosynthesis, use light to make sugars to survive.
vent hot topics: vent names
As new features and landmarks are discovered in the scientific community, the lead discoverer usually gets the privilege of naming it, such as Mount Rushmore. Same goes for hydrothermal vents found in the ocean. However, not all names given are entirely scientific, in fact, few are. The names of countries, cities, states, rivers and mountains, are usually named after people or words of native languages. Although, some go a bit farther than others. Some interesting names given to hydrothermal vents -that are officially recognized in the marine scientific community- include Godzilla, Mothra, Hulk, Boomer, Mammoth, Cathedral, Organ Pipe, Sasquatch, Tweety, Scooby, Road Runner and, yes, Homer Simpson.