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The Gutenberg discontinuity occurs within Earth's interior at a depth of about 2,900 km (1,800 mi) below the surface, where there is an abrupt change in the seismic waves (generated by earthquakes or explosions) that travel through Earth. At this depth, primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves ...
The core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron–nickel outer core, at a depth of 2,891 km (1,796 mi) below Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the differences between the acoustic impedances of the solid mantle ...
This sharp decline is observed at the core-mantle boundary, also referred to as the D'' region or Gutenberg discontinuity. [12] Furthermore, the reduction in seismic velocity in the outer core suggests the presence of lighter elements like oxygen, silicon, sulfur, and hydrogen, which lower the density of the outer core. [38] [39] [40] [41]
core–mantle boundary. outer core–inner core boundary. Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon 's radius. [1][2] There are no samples of Earth's core accessible for direct ...
The Lehmann discontinuity is an abrupt increase of P -wave and S -wave velocities at the depth of 220 km (140 mi) in Earth's mantle, discovered by seismologist Inge Lehmann. [2][3][4] The thickness is 220 km [citation needed]. It appears beneath continents, but not usually beneath oceans, [5] and does not readily appear in globally averaged ...
t. e. A seismic shadow zone is an area of the Earth 's surface where seismographs cannot detect direct P waves and/or S waves from an earthquake. This is due to liquid layers or structures within the Earth's surface. The most recognized shadow zone is due to the core-mantle boundary where P waves are refracted and S waves are stopped at the ...
Inge Lehmann. Inge Lehmann ForMemRS (13 May 1888 – 21 February 1993) was a Danish seismologist and geophysicist who is known for her discovery in 1936 of the solid inner core that exists within the molten outer core of the Earth. The seismic discontinuity in the speed of seismic waves at depths between 190 and 250 km is named the Lehmann ...
The seismic velocities very near the surface (≲ 220±30 km) are markedly lower than at greater depths, demarking the LVZ. The low-velocity zone (LVZ) occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle. It is characterized by unusually low seismic shear wave velocity compared to the surrounding depth ...