The electric Moho

摘要: Since Mohorovicic1 discovered a dramatic increase in compressional seismic velocity at depth of 54 km beneath the Kulpa Valley Croatia, ‘Moho’ has become arguably most important seismological horizon Earth owing to its role defining crust–mantle boundary. It is now known be ubiquitous feature Earth, being found both continents and oceans, commonly assumed separate lower-crustal mafic rocks from upper-mantle ultramafic rocks. Electromagnetic experiments conducted date, however, have failed detect corresponding change electrical conductivity base crust, although one might expected on basis laboratory measurements2. Here we report electromagnetic data Slave craton, northern Canada, which show step-change Moho depths. Such resolution possible because craton highly anomalous, exhibiting total crustal conductance less than 1 Siemens—more an order magnitude smaller other Archaean cratons. We also that uppermost continental mantle directly two orders more conducting studies olivine would suggest, inferring there must connected phase.