Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed. Two plates sliding past each other forms a transform plate boundary. One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater.
Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Then, plant and animal remains mix with these eroded rocks to create fertile soil. Together, these systems shape every environment on Earth.
In tall mountain ranges of the lithosphere, the thinner air and precipitation combine to create a cool or even icy climate zone. Wind wears down rocks into sandy deserts. Healthy soil and rain make it easy for living things to grow in the forest. Plants and animals have adapted over time to fit these unique environments. An adaptation is passed from generation to generation.
The Earth is the only place in the known universe that supports life. Also called lithospheric plate.
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Weathering is the process of the weakening and breakdown of rocks, metals, and manmade objects. There are two main types of weathering: chemical and physical.
An example of chemical weathering is acid rain. Caused mostly by the burning of fossil fuels, acid rain is a form of precipitation with high levels of sulfuric acid, which can cause erosion in the materials in which it comes in contact. Plates move as rigid bodies, so it may seem surprising that the North American Plate can be moving at different rates in different places.
The explanation is that plates move in a rotational manner. The North American Plate, for example, rotates counter-clockwise; the Eurasian Plate rotates clockwise.
Boundaries between the plates are of three types: divergent i. The plates are made up of crust and the lithospheric part of the mantle Figure Plates are thought to move along the lithosphere-asthenosphere boundary, as the asthenosphere is the zone of partial melting. It is assumed that the relative lack of strength of the partial melting zone facilitates the sliding of the lithospheric plates.
At spreading centres, the lithospheric mantle may be very thin because the upward convective motion of hot mantle material generates temperatures that are too high for the existence of a significant thickness of rigid lithosphere Figure The fact that the plates include both crustal material and lithospheric mantle material makes it possible for a single plate to be made up of both oceanic and continental crust.
Similarly the South American Plate extends across the western part of the southern Atlantic Ocean, while the European and African plates each include part of the eastern Atlantic Ocean. The Pacific Plate is almost entirely oceanic, but it does include the part of California west of the San Andreas Fault. Divergent boundaries are spreading boundaries, where new oceanic crust is created from magma derived from partial melting of the mantle caused by decompression as hot mantle rock from depth is moved toward the surface Figure Most divergent boundaries are located at the oceanic ridges although some are on land , and the crustal material created at a spreading boundary is always oceanic in character; in other words, it is mafic igneous rock e.
Some of the processes taking place in this setting include:. Spreading is hypothesized to start within a continental area with up-warping or doming related to an underlying mantle plume or series of mantle plumes.
When a series of mantle plumes exists beneath a large continent, the resulting rifts may align and lead to the formation of a rift valley such as the present-day Great Rift Valley in eastern Africa. It is suggested that this type of valley eventually develops into a linear sea such as the present-day Red Sea , and finally into an ocean such as the Atlantic.
It is likely that as many as 20 mantle plumes, many of which still exist, were responsible for the initiation of the rifting of Pangea along what is now the mid-Atlantic ridge see Figure Convergent boundaries, where two plates are moving toward each other, are of three types, depending on the type of crust present on either side of the boundary — oceanic or continental.
The types are ocean-ocean, ocean-continent, and continent-continent. Read the latest volcano activity updates around the world. Notre nouveau livre. Volcano Discoveries "One of the most eye-catching guides to the world's volcanoes ever published.
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