By Sid Perkins
Analyses of seismic waves that travel deep within Earth may resolve a decades-old debate about the thickness of the planet’s continents.
Some studies have suggested that the major landmasses in Earth’s rigid outer shell–including the planet’s crust and the upper layers of its mantle–are between 200 and 250 kilometers thick. To arrive at those estimates, researchers considered phenomena such as heat flow from within the planet.
Other investigations, particularly analyses of seismic waves traveling through and just under those landmasses, have indicated that the continents may be up to 400 km thick.