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As oceanic crust moves away from the shallow mid-ocean ridges, it cools and sinks as it becomes more dense. This increases the volume of the ocean basin and decreases the sea level.
Trenches are formed by subduction, a geophysical process in which two or more of Earth’s tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression.
The surface of the Earth is made of interlocking tectonic plates. The tectonic plates are always moving in relation to each other. When two plates pull away from each other, the seafloor spreads along the boundary of the two plates. At the same time, it contracts in another area.
Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth’s tectonic plates spread apart. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.
Why are there virtually no sediments at ocean ridges, even when they are close to land? A) The sediments get buried by volcanic rocks, so are not visible.
The material that erupts at spreading centers along the mid-ocean ridge is primarily basalt, the most common rock on Earth. Because this spreading occurs on a sphere, the rate separation along the mid-ocean ridge varies around the globe.
Fast-moving spreading ridges tend to be more gently sloped than slow-moving ridges. True Deep-sea trenches are found at convergent plate boundaries.
Confirmation of seafloor spreading was supported by the: parallel to and symmetric about ocean ridges. The seafloor magnetic pattern is be best described as: thermal contraction of hot lithosphere. Oceans become deeper moving away from ridges due to:
Differences in height between continental crust and oceanic crust are explained by: The asthenosphere is composed of outer mantle material. Which of the following statements is true of the asthenosphere?
Both convergent plate boundary & divergent plate boundary ancient precursor of the Pacific Ocean Panthalassa supercontinent 200 million years ago Pangea depression along ridge axis rift valley study of changes in the character of oceans due to geographic changes paleoceanography study of magnetism over geologic time paleomagnetism True