The modern geologist with no knowledge of geochemistry will be severely limited. Indeed, geochemistry now pervades the discipline—providing the basis for measurement of geologic time, allowing critical insights into the Earth’s inaccessible interior, aiding in the exploration for economic resources, understanding how we are altering our environment, and unraveling the complex workings of geochemical systems on the Earth and its neighboring planets. Geochemical reasoning reveals both processes and pathways, as the book’s title implies.

Geochronology, including thermochronology, is an essential component of practically all modern Earth and planetary science and provides fundamental information for many other areas, including archeology, marine sciences, and ecology. Geochronology establishes the timing of critical events ranging from the age of the Earth to stratigraphic boundaries, and it provides unique constraints on the pace and dynamics of processes ranging from condensation of the solar nebula to planetary differentiation to surface exposure to biologic evolution. Given that Earth and planetary scientists commonly seek to understand relationships between events or phenomena for which physical evidence is incomplete or ambiguous, establishing temporal relationships through geochronology often provides a substantial basis for causality arguments.

Although the concept of geochronology has existed for millennia, and the particular name has been around since 1893, most scientists would probably agree that the modern practice or discipline is based on application of radioisotopic (or cosmogenic) systems in natural materials, which has existed for only a little more than a century (or less). Even into the 20th century, the geologic timescale floated freely in time. Geologists had established sequences of evolutionary and orogenic events in the rock record, but numerical estimates ranged widely, more so further back in geologic history. Without precise dates, only poorly constrained arguments could be made about the relative durations and the time separating major events in the geologic record. Likewise, prior to radioisotopic methods, the best available estimates for the age of the Earth (and solar system) disagreed by several orders of magnitude. The rather sudden recognition of nuclear structure and radioactive decay around the beginning of the 20th century, changed Earth and planetary science fundamentally. The very first radioisotopic dates measured increased the previously deduced minimum age of the Earth by about an order of magnitude, and subsequent work, less than 100 years ago, increased it by another factor of ten. <...>

Modern geodesy as discussed in this volume started with the development of distance measurement using propagating electromagnetic signals and the launch of Earth-orbiting satellites. With these developments, space-based geodesy allowed global  measurements of positions, changes in the rotation of the Earth, and the Earth’s gravity field. These three areas, positioning, Earth rotation, and gravity field, are considered the three pillars of geodesy. The accuracy of current measurement systems allows time variations to be observed in all three areas. Also, the complexity of problems is such that each of the pillars interacts with each other and with many other branches of Earth science. This interaction is most apparent in the role that water plays in modern geodetic measurements.

Бониниты во времени и пространстве: петрогенезис и геодинамические обстановки образования

Длиннопериодные изменения в соотношении процессов тектоно-плитного и мантийно-плюмового происхождения в докембрии

Раннепалеозойский базитовый магматизм на северо-востоке Сибирского кратона

Неотектоника Охотского моря

Строение и история абиссальных холмов северо-западной плиты Пацифики по данным непрерывного сейсмического профилирования и сейсмостратиграфии