In 1968, the research vessel Glomar Challenger ventured on a year-long scientific expedition, between South America and Africa and drilled core samples at specific locations assigned to it. When tested, these samples provided the conclusion that proved the seafloor spreading hypothesis to be true. The JOIDES Resolution is a deep-sea drilling ship of the 1990s. This ship is capable of carrying more than 9,000 m of drill pipe. It is also known for its precise positioning and deeper drilling than the Glomar Challenger.
According to the maps and diagrams on the website, where are the major concentrations of the world's earthquakes? Where do most of the earthquakes in Europe occur?
The most important concentration of earthquakes occurs in the region so called Ring of Fire, which encircles the rim of the Pacific Ocean. Approximately 80% of the world’s shallow-focus quakes, 90% of the intermediate-focus quakes, and nearly 100% of the deep-focus quakes occur in this realm. Another realm is the Mediterranean-Himalayan belt: a major concentration of earthquakes which runs through the Mediterranean Sea, crosses the Middle East and the Himalayas, and passes through the East Indies to meet the circum-Pacific belt north of Australia.
The boot-shaped Italian peninsula is one of the most earthquake-prone regions in Europe. Although most of the quakes tend to be low-level events, an occasional one with a magnitude of 6.0 or higher can cause extensive damage to traditional stone and block structures. The entire northern side of the Mediterranean Basin is earthquake prone.
What undersea hot springs were discovered in 1977? What is remarkable about these (and other) undersea hot springs?
In 1977, hot springs at a depth of 2.5 km, on the Galapagos Rift off the coast of Ecuador were discovered. The most remarkable feature of the hot springs is that the waters around these deep-ocean hot springs, which can be as hot as 380 °C, are home to a unique ecosystem like giant tube worms, huge clams, and mussels. Also the undersea hot springs are said to contain an abundance of dark-colored ore minerals (sulfides) of iron, copper, zinc, nickel, and other metals called "black smokers."
Briefly define the four types of plate boundaries and give an example of each.
The four types of plate boundaries are classified into:
Divergent boundaries, Convergent boundaries, Transform boundaries and Plate boundary zones.Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle. The best known of the divergent boundaries is the Mid-Atlantic Ridge. This submerged mountain range extends from the Arctic Ocean to beyond the southern tip of Africa.
Convergent boundaries are formed as a result of the crust getting destroyed as one plate dives under another. Convergence can occur between an oceanic and a largely continental plate like the subduction zone between the Nazca Plate and the South American Plate, or between two largely oceanic plates similar to the fast-moving Pacific Plate which converged against the slower moving Philippine Plate, or between two largely continental plates comparable to the collision between the Indian and Eurasian plates which pushed up the Himalayas and the Tibetan Plateau.
Transform boundary is the zone between two plates sliding horizontally past one another. Hence, the crust is neither produced nor destroyed. For example, the San Andreas Fault zone in California.
Plate boundary zones are broad belts in which boundaries are not well defined and the effects of plate interaction are unclear. One of these zones marks the Mediterranean-Alpine region between the Eurasian and African Plates, within which several smaller fragments of plates (microplates) have been recognized.
What is the Ring of Fire?
The Ring of Fire is a direct result of plate tectonics and the movement and collisions of lithospheric plates. A string of 452 volcanoes stretches from the southern tip of South America, up along the coast of North America, across the Bering Strait, down through Japan, and into New Zealand. The Andes in South America, the Cascade Range of North America, and the Southern Alps of New Zealand are all associated with the Ring of Fire. It is the most seismically and volcanically active zone in the world. About 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire. It is sometimes called the circum-Pacific belt or the circum-Pacific seismic belt.
What are hot spots? Where are some prominent hot spots?
Hot spots are volcanic regions fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. They may be unanimously hot, and provide a great deal of molten magma. The magma, which is lighter than the surrounding solid rock, then rises through the mantle and crust to erupt onto the seafloor, forming an active seamount. Over time, countless eruptions cause the seamount to grow until it finally emerges above sea level to form an island volcano.
Hawaii, Azores, Afar, Yellowstone, Galápagos, and Iceland are some of the prominent hot spots.
