At subduction zones, the oceanic plate is pushed down, or subducted, below the continental lithosphere. When the boundary is between an oceanic plate and a continental plate, it is also referred to as a destructive plate boundary. A convergent, or destructive, boundary showing subduction of an oceanic plate under a continental plate. This type of boundary is called a convergent boundary and is dominated by reverse faulting, although other types of faulting may be observed. Plates can move towards each other at a boundary. Divergent boundaries are associated with volcanic activity and the earthquakes in these zones tend to be frequent and small.Ĭontinental collisions result in the creation of mountains and fold belts as the rocks are forced upwards. Examples include the East African rift and mid-ocean ridges where two ocean plates are moving apart, such as the regions near the Azores and Iceland. Earthquakes occur along the fractures that appear as the plates move apart. Hot magma rises from the mantle at mid-ocean ridges, pushing the plates apart. You can see normal faulting at the surface where the Mid-Atlantic Ridge crosses Iceland. The Mid-Atlantic Ridge is a good example of a constructive plate boundary. This type of boundary is dominated by normal faulting, although other types of faulting may be observed.Ī divergent, or constructive, plate boundary, where new material is produced at the surface. It is also referred to as a constructive plate boundary, as new material is being produced at the boundary surface. This type of boundary is called a divergent boundary. However, ridge push is also presented in recent research to be a force that drives the movement of plates. Research has shown that the major driving force for most plate movement is slab pull, because the plates with more of their edges being subducted are the faster-moving ones. slab pull: older, colder plates sink at subduction zones because, as they cool, they become more dense than the underlying mantle and the cooler, sinking plate pulls the rest of the warmer plate along behind it.ridge push (buoyant upwelling mantle at mid-ocean ridges): newly formed plates at oceanic ridges are warm, so they have a higher elevation at the oceanic ridge than the colder, more dense plate material further away gravity causes the higher plate at the ridge to push away the lithosphere that lies further from the ridge.mantle convection currents: warm mantle currents drive and carry plates of lithosphere along a like a conveyor belt.Three of the forces that have been proposed as the main drivers of tectonic plate movement are: There are a number of competing theories that attempt to explain what drives the movement of tectonic plates. The asthenosphere behaves like a fluid over very long time scales. What drives the movement of tectonic plates?īelow the tectonic plates lies the Earth’s asthenosphere. Observations show that most earthquakes are associated with tectonic plate boundaries and the theory of plate tectonics can be used to provide a simplified explanation of the global distribution of earthquakes, while some of the characteristics of earthquakes can be explained by using a simple elastic rebound theory. Tectonic plates move very slowly relative to each other, typically a few centimetres per year, but this still causes a huge amount of deformation at the plate boundaries, which in turn results in earthquakes. These slabs form the lithosphere, which is comprised of the crust (continental and oceanic) and the upper part of the mantle. The Earth’s outermost layer is fragmented into about 15 major slabs called tectonic plates. We also know that the outer part of the core is liquid, because S-waves do not pass through it. The core is composed of iron and we know that it exists because it refracts seismic waves creating a ‘shadow zone’ at distances between 103º and 143º. What are we doing about climate change?Īt a depth of about 2900 km is the boundary between the mantle and the Earth’s core.Understanding carbon capture and storage.What causes the Earth’s climate to change?.NGR hydrocarbons (well samples) database.Palaeontology and biostratigraphy collections.Donations and loans of materials collections.Engineering and Geotechnical Capability.Integrated resource management in Eastern Africa.Rock Volume Characterisation Laboratory Cluster.Fluid and Rock Processes Laboratory Cluster.Equality, diversity and inclusion at BGS.Environmental policy and sustainability strategy.
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