Long-term interactions between increasing and decreasing secular trends in Earth evolution have produced a geologic record of steady-state equilibrium that is punctuated by nonrecurring events and variations in Earth's endogenic heat loss decipherable as ∼0.5-b.y. cycles in orogeny, rift magmatism, and platform sedimentation. A detailed record for the past 0.6 b.y. has permitted construction and testing of a heat-driven model of plate-tectonic episodicity that reproduces major tectonic, biogeochemical, and isotopic trends for the Phanerozoic. Application to the Proterozoic record reveals clues on the relationship of tectonic processes to the life-mediated history of Earth's atmosphere, hydrosphere, and crust.