The crust which is heavier is usually the one that moves underneath the lighter crust. Whenever this happens, one of the plates starts to move underneath the other one. This means they are characterized by two plates moving towards each other. For those that didn’t, convergent boundaries happen in places where two plates meet. You probably already guessed what type of movement occurs in these boundaries. The Horn of Africa is a famous example of a rift zone. The plates start pulling away from each other and lava is released to create a new crust. The thing that is common in rift zones is high volcanic activity. The area between the plates is known as the rift zone. This movement is the plates pulling away from each other. Divergent Boundariesĭivergent boundaries occur when a specific movement happens between the plates. These boundaries describe how the plates are moving, which is what we will be talking about in this article. There are 4 different types of tectonic plate boundaries. These plates move and interact with each other, and today we already know plenty about them. These studies describe the crust of our planet as being made up of different plates. This theory gave birth to modern studies of plate tectonics. At first the majority of scientists were highly critical of his work, and it was not until the 1960s that it was accepted as scientifically true. However, in 1915, Alfred Wegener presented the theory of continental drift. Understanding how the plates in our planet’s crust move, was something scientists struggled with for years. It is a dynamic structure and this can be best seen whenever an earthquake occurs. In the interior of plates, this condition is usually not given.The crust of our planet is constantly evolving and changing. Not only larger amounts of melt are needed to produce volcanoes on the surface, but also suitable passageways, in forms of cracks and fractures through the rigid crust must exist or be created by the pressure of larger amounts of magma. The normal amount of melt that may be present in the asthenosphere under a normal plate is obviously too small to produce volcanoes on the surface (otherwise there would be volcanoes all over) and is in equilibrium with its surroundings. Magma must rise to the surface to make a volcano The asthenosphere lies between about 100 km and 35 km depth and is composed of hot, weak material that may contain a few percent of partial melts or is near the point to produce melts. This constellation is only given in the uppermost layers of the mantle, beneath the lithosphere, in a zone called the asthenosphere (Greek: "asthenos" = weak). (Partial) melting of mantle rock is only possible if the temperature's tendency to melt rock exceeds the opposing effect of pressure. Within the hot mantle, however, there is a different problem to produce magmas: pressure. Pressure keeps (most of) the mantle solid by magma with much higher temperatures intruding from underneath, small amounts of crust can be melted as well. The solid crust would generally be too cold to produce melts. Most magmas (molten rock) originate directly from the mantle. But it is the theory of Plate Tectonics to allow explaining the deeper relationship between the two phenomena and explaining both of them in a single unifying theory. Volcanism at divergent and convergent plate margins (USGS)A connection between earthquakes and volcanic activity has probably been suspected since the earliest history of mankind. The most famous example is the San Andreas Fault in California, where the Pacific and the North-American plates move along each other. Strong earthquakes can occur along these faults. Transform boundaries occur where two lithospheric plates slide past each other along transform faults. Earthquakes trace path of downward-moving plate as it descends into asthenosphere. Western South America) where the dense oceanic lithosphere sinks beneath the less dense continental plates. Subduction zones include the boundaries of the Pacific plate (e.g. If the process of rifting on a continent continues long enough, it can break up the continent and form a new oceanic basin separating the parts.Ĭonvergent boundaries occur where two plates slide towards each other to form either a subduction zone (if one plate, normally an oceanic plate moves underneath the other) or a continental collision. Divergent boundaries on continents are more rare, but also exist. Examples are the Mid-Atlantic Ridge and East Pacific Rise. This happens at the mid-ocean ridges, where seafloor spreading and volcanic activity continuously add new oceanic crust to the oceanic plates on both sides. Types of plate boundariesThere are 3 types of plate boundaries, depending on how the plates move relative to each other:ĭivergent boundaries occur where two plates move apart from each other.
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