Time series analysis is used to investigate the temporal behavior of a variable x(t). Examples include investigations into long-term records of mountain uplift, sea level fluctuations, orbitally induced insolation variations (and their influence on glacial—interglacial cycles), millennium-scale variations in the atmosphere—ocean system, the effect of the El Niño—Southern Oscillation on tropical rainfall and sedimentation (Fig. 5.1), and tidal influences on noble gas emissions from boreholes. The temporal pattern of a sequence of events can be random, clustered, cyclic, or chaotic.