Nuclear reactions are going on continuously in all matter in the universe. In fact, it would be difficult to find a site which is devoid of nuclear reactions. The rates of reactions are, however, often very low so that their studies require very sensitive techniques for the measurement of the included nuclear isotopic changes. Recent advances in the field of accelerator mass spectrometry have now made it possible to sensitively measure several isotopic ratios for long lived radionuclides, e.g. 10Be/9Be, 36Cl/Cl and 26Al/Al, 14C/C, at ratios of ≥ 10-15-10-14. This accomplishment has now made it possible to measure a suite of radionuclides produced by cosmic rays and radiogenic energetic particles in a variety of materials. Cosmogenic and nucleogenic 3He has been studied recently in several terrestrial solids as a result of recent advances in mass spectrometry and selective 3He extraction methods. As a consequence of these developments, it is now possible to study the evolutionary history of a host of surficial materials, and the rates of diverse geophysical/geochemical processes. In the paper, these developments are briefly reviewed, and the new nuclear methods for the study of soil erosion and formation rates are discussed.