Gutenberg discontinuity
Also called: Core-mantle boundary · Topic: Interior of the Earth: Earthquakes, Volcanoes and the Layered Earth · NCERT: Class 11, Ch 3 "Interior of the Earth"
Meaning
The Gutenberg discontinuity is the boundary between the mantle and the outer core, about 2,900 km deep. Beno Gutenberg identified it in 1913. Below it, the outer core is liquid. So S-waves stop here, because they can pass only through solids. P-waves slow down and bend sharply as they enter the core. This bending creates the P-wave shadow zone between 105° and 145° from the epicentre.
Example
After the Bhuj earthquake in Gujarat (2001), seismographs more than 105° away recorded no S-waves. The waves had been stopped at the Gutenberg discontinuity.
Don't confuse with
- Lehmann discontinuity: the boundary between the liquid outer core and the solid inner core, about 5,150 km deep, found by Inge Lehmann in 1936.
- Mohorovicic discontinuity (Moho): the boundary between the crust and the mantle, found in 1909, only 5-70 km deep.