Conrad discontinuity
Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Beyond NCERT
Meaning
The Conrad discontinuity is a boundary inside the continental crust. Above it is the lighter granitic upper crust (sial: rich in silica and aluminium). Below it is the denser basaltic lower crust (sima: rich in silica and magnesium). Seismic waves change speed when they cross it, which is how it is detected. Its depth varies, and it is not found everywhere.
Example
Victor Conrad, an Austrian scientist, picked out this boundary by studying earthquake waves recorded in the Eastern Alps of Austria.
Don't confuse with
- Mohorovicic discontinuity (Moho): this is the boundary between the crust and the mantle. The Conrad discontinuity lies inside the crust and is found only under continents.