Structure of the Earth 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 the gravitational and magnetic fields of the Earth, and experiments
International Association for Engineering Geology and the Environment large projects and in the assessment and remediation of environmental issues, an update of the first statutes of the association was deemed necessary. The second statutes were approved by the general assembly in Kyoto (Japan) in 1992. A new definition of engineering geology was given, which reflected the experience collected during the previous 25 years and read as follows: "“Engineering geology is a science devoted to the investigation, study and solution of engineering and environmental problems which may arise as the result of the interaction between geology and the works and activities of man as well as to the prediction