The birth and evolution of Earth reference models

Earth reference models provide a systematic description of the spatial distribution of primary physical properties within the Earth’s interior, serving as the fundamental framework for revealing internal structures and understanding the planet’s composition and evolution. The evolutionary trajectory of Earth reference models is characterized by four key stages: (1) the discovery of major internal interfaces; (2) the proposal of preliminary structural frameworks; (3) the establishment of comprehensive one-dimensional (1D) reference models; and (4) the construction of three-dimensional (3D) models. This succession of models has profoundly advanced our understanding of deep Earth interior. By reviewing seminal papers on the inception and development of Earth reference models, this article revisits the exploratory journeys undertaken by both pioneering and contemporary scholars. It provides a systematic overview of the significance and historical background of model construction, the research strategies and methodologies employed during the development of representative models, exemplified by the preliminary reference Earth model (PREM), as well as their scientific innovations and impacts. Furthermore, the endeavors trace the evolution of Earth reference models from 1D radial profiles to 3D structural representations and offer perspectives on future research directions. By analyzing the strategies and methods adopted during these explorations, this work provides insights and inspiration for addressing complex scientific challenges in Earth sciences and other domains.