Earth

Andreas Fichtner explains progress and obstacles in seismic imaging of Earth at regional and global scales. He discusses the evidence supporting three-dimensional maps of mantle plumes, continental interiors, mid-ocean ridges and large low-shear-velocity structures, and how improved methods increase confidence in the images.

Stephen Porder explores how living organisms have transformed Earth through their use of hydrogen, oxygen, carbon, nitrogen and phosphorus. Drawing on his book Elemental, the conversation connects these biogeochemical changes across deep time with sustainability and choices that could reduce human environmental impacts.