On two types of supercontinental cyclicity

Analysis of tectonic events during the last 3 Ga of the Earth’s evolution, when 400 Ma global supercontinent cyclicities dominated, identified two types of supercontinental cycles. These types differ by the degree of breakup of a supercontinent that starts a cycle. Supercontinental cycles of the first type are characterized by a scattered and relatively even global distribution of the supercontinent split into numerous continents and oceans. Supercontinental cycles of the second type are characterized by uneven “incomplete” supercontinental breakups, which are localized alternately in either the Northern or the Southern Hemisphere, whereas a significant part remains after the breakup. These supercontinental cycle types followed each other composing pairs of megacycles that were 800 Ma long until ca. 700 Ma. Every megacycle consisted of two supercontinental cycles of different types; however, after the breakup of Rodinia, virtually only the second type of supercontinental cycle has been observed. The different degrees of the breakup of supercontinents, which are reflected in the two supercontinental-cycle types, may be caused by uneven heating of the mantle produced by supercontinents owing to the thermal blanket effect.