Structure of the Earth decay of radioactive elements, and freezing of the inner core. Structure of the Earth The internal structure of the Earth is layered in spherical shells: an outer silicate solid crust, a highly viscous asthenosphere and mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. Scientific understanding of the internal structure of the Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of
How the Snake Lost Its Legs many of the, "nuts and bolts of evolution, deeper than just natural selection," are on display in the book, revealing, "precisely what genetic/physiological mechanisms are being selected for." The molecular biologist Arnaud Martin observes that, "As children, we have all wondered about 'the How and the Why' of animal features, and if you are reading this it is in fact quite possible that a similar inquisitiveness still burns within you. The tone of "How the Snake Lost its Legs" finds its roots in the famous "Just So Stories" of Joseph Rudyard Kipling by tickling this curiosity with the formulaic "How