What's the lowdown on the asthenospheric dome that can produce rift valleys?

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Offline whalejail

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Hello. I'm a geological novice trying to understand why different land formations occur. The second-to-last paragraph in the "Rift Valleys" section of the Brittanica article on rift valleys/tectonic basins reads:

Some rift valleys, such as the East African Rift Valley in Ethiopia and Kenya, have formed over large domes. Upwelling of hot material within the underlying asthenosphere not only pushes the overlying lithosphere up but heats it as well, causing it to expand. To some extent the upward bulging of the lithosphere causes it to stretch, and this stretching manifests itself as a rift valley. Rift valleys that have formed in this way are commonly associated with extensive volcanism.

I'm having trouble narrowing down what this phenomenon is (beyond an upwelling of hot material) so I can get more information about how or why this happens. Is it (forgive me if I throw these terms around wrongly) a diapir? Is it related to a mantle plume? Is it a phenomenon that lacks a name for itself, but can be understood by learning more about the general mechanics of the asthenosphere's interaction with the lithosphere? If so, does that area of inquiry have a specific name I can punch into Google and read about? Clearly, it's hot in the asthenosphere and that results in landforms changing, but I don't know how frequent these domes are, what size they tend to be, what heating mechanics cause them to form, etc.

I'd like to be able to understand this process more, and any links, leads or suggestions would be appreciated.
« Last Edit: 18/03/2016 13:57:24 by whalejail »


Offline evan_au

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I think it is fair to say that there are competing theories.
The asthenosphere has convection currents, which disturb the more solid rocks of the surface (lithosphere).

Detecting plumes of hot rock requires a high density of seismographs that can reconstruct the propagation velocity of earthquake waves in the mantle and asthenosphere. From this it may be possible to determine the temperature, density and velocity of the rock.

There may be pre-existing weaknesses in the lithosphere due to boundaries of older continental plates (cratons).

See: http://en.wikipedia.org/wiki/East_African_Rift#Competing_theories_on_geologic_evolution