Interpreting Earth history. A manual in historical geology / Интерпретация Земной истории. Руководство по исторической геологии

The discovery of “deep time” is one of geology’s greatest contributions to human understanding. The conceptual foundations laid by eighteenth- and nineteenth-century geologists working in relatively small geographic areas paved the way for development of the modern high-resolution geological timescale (figure 1.1), which spans 4.6 billion years of Earth history and applies to geological features anywhere on Earth. The succession of eons, eras, and periods was constructed during the early part of the nineteenth century using the principles of relative dating that are the focus of this exercise. The absolute timescale (numerical scale) was added after the discovery of radioactivity and the development of techniques that were able to reliably measure small amounts of radiogenic isotopes in geological materials. The numerical scale, the subject ofexercise 2, was developed during the latter half of the twentieth century <...>