What is a convection current?
There is debate as to whether the rest of the mantle, especially the lower mantle, has the same bulk composition . The mantle composition has changed throughout Earth history due to the extraction of oceanic and continental crust.
The geothermal gradient of the mantle increases rapidly in the thermal boundary layers at the top and bottom of the mantle, and increases gradually through the interior of the mantle. The pressure in the mantle increases from a few kbar at the Moho to kbar GPa at the core-mantle boundary .
Mantle convection This figure is a snapshot of one time-step in a model of mantle convection. Colors closer to red are hot areas and colors closer to blue are cold areas. In this figure, heat received at the core—mantle boundary results in thermal expansion of the material at Convection current hypothesis bottom of the model, reducing its density and causing it to send plumes of hot material upwards.
Likewise, cooling of material at the surface results in its sinking. Because of the temperature difference between the Earth's surface and outer core and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle.
Downward motion of material occurs at convergent plate boundaries called subduction zones. Locations on the surface that lie over plumes are predicted to have high elevation because of the buoyancy of the hotter, less-dense plume beneath and to exhibit hot spot volcanism.
The volcanism often attributed to deep mantle plumes is alternatively explained by passive extension of the crust, permitting magma to leak to the surface the "Plate" hypothesis.
Plate motion should not be confused with continental drift which applies purely to the movement of the crustal components of the continents. The movements of the lithosphere and the underlying mantle are coupled since descending lithosphere is an essential component of convection in the mantle.
The observed continental drift is a complicated relationship between the forces causing oceanic lithosphere to sink and the movements within Earth's mantle. Although there is a tendency to larger viscosity at greater depth, this relation is far from linear and shows layers with dramatically decreased viscosity, in particular in the upper mantle and at the boundary with the core.
The mantle is considered to be viscous and incapable of brittle faulting. A number of mechanisms have been proposed to explain this phenomenon, including dehydration, thermal runaway, and phase change. Thus, the upper mantle can only flow very slowly.
However, when large forces are applied to the uppermost mantle it can become weaker, and this effect is thought to be important in allowing the formation of tectonic plate boundaries. Exploration Exploration of the mantle is generally conducted at the seabed rather than on land because of the relative thinness of the oceanic crust as compared to the significantly thicker continental crust.
The first attempt at mantle exploration, known as Project Moholewas abandoned in after repeated failures and cost over-runs. On 5 Marcha team of scientists on board the RRS James Cook embarked on a voyage to an area of the Atlantic seafloor where the mantle lies exposed without any crust covering, midway between the Cape Verde Islands and the Caribbean Sea.'Convection' as we know, is a process of heat-transfer which particularly takes place in fluids and liquids.
According to this hypothesis, it is believed that the mantle (intervening layer between the crust and core) is made up of molten silicates and therefore in this medium heat is transmitted by convectional process.
A response to Don Scott's "The Electric Sun" webpage, this webpage of mine is as yet incomplete, and therefore a "work in progress".It is not my intention, at least for now, to address the issues raised, and alleged to be in favor of the electric-sun hypothesis.
The Thermal Convection Current hypothesis dates back to Hopkins () and Fisher (), but credit goes to Arthur Holmes for presenting more elaborately the same as a force for mountain building, continental drift, volcanism and formation of ocean trenches etc.
Sep 02, · Heat Convection in Liquids ( ratings) Convection currents form, which are streams of gas or liquid powered by convection. Some of this movement is caused by differences in density.
You might remember that density how much matter there is in a given amount of space.
In this convection current experiment for kids, /5(). Abiogenesis, or informally the origin of life, is the natural process by which life arises from non-living matter, such as simple organic compounds.
The transition from non-living to living entities was not a single event, but a gradual process of increasing complexity that involved molecular self-replication, self-assembly, autocatalysis and cell membranes.
Convection currents can be found in the boiling of liquid, the heat of a campfire, the weather, and even the magma in the earth.
Quick Notes Convection currents are formed by the difference in.