Earth science events have spatial, temporal and spatio-temporal variabilities depending on the scale and the purpose of the assessments. Various earth sciences branches such as hydrogeology, engineering geology, petroleum geology, geophysics, and related topics have, in general, spatio-temporal variabilities that need for effective modeling techniques for proper estimation and planning the future events in each branch according to scientific principles. Determinism and especially uncertainty techniques are frequently used in the description and modeling these events conveniently through simple and rather complicated computer software. However, the basic principles in any software require simple and effective mathematical, probabilistic, statistical, stochastic and recently fuzzy methodologies or their combination for an objective solution of the problem based on field or laboratory data. This chapter provides comparetive and simple explanation of each one of these approaches.