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All tectonic processes are driven by gravitational force when density differences are present. A good example of this would be the large-scale circulation of the Earth's mantle. Lateral density variations near the surface (such as the creation, cooling, and subduction of oceanic plates) also drive plate motion.
With crustal extension, a series of normal faults which occur in groups, form in close proximity and dipping in opposite directions. [4] As the crust extends it fractures in series of fault planes, some blocks sink down due to gravity, creating long linear valleys or basins also known as grabens, while the blocks remaining up or uplifted produce mountains or ranges, also known as horsts.
A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km (3 mi), from canyon floor to canyon rim, as with the Great Bahama Canyon. [1]
A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny . [ 1 ]
Both terrain higher than the measurement point and valleys lower than the measurement point reduce the measured value of gravity. This is taken into account by the terrain correction g T. The terrain correction is calculated from knowledge of the local topography and estimates of the density of the rock making up the high ground.
Understanding the principle of isostasy is a key element to understanding the interactions and feedbacks shared between erosion and tectonics. The principle of isostasy states that when free to move vertically, lithosphere floats at an appropriate level in the asthenosphere so that the pressure at a depth of compensation in the asthenosphere well below the base of the lithosphere is the same. [3]
Higher blocks are called horsts, and troughs are called grabens. A spreading apart of the surface causes tensional forces. A spreading apart of the surface causes tensional forces. When the tensional forces are strong enough to cause a plate to split apart, it does so such that a center block drops down relative to its flanking blocks.
This would subsequently produce continents composed of komatiite, an ultramafic rock rich in magnesium with a high melting point and low dynamic viscosity. [12] Another line of research follows up on this, proposing that differences in the densities of newly formed crystals caused separation of crustal rocks; upper crust largely composed of ...