Archean tectonics

Tectonic processes on Earth during the Archean eon (4.0-2.5 billion years ago), when a hotter mantle may have driven different plate behavior.

Vertical tectonics: Deformation driven by crustal thickening, sagduction and delamination rather than lateral plate motion. The leading alternative to horizontal plates for explaining Archean deformation.
Hadean Earth: The interval before 4.0 billion years ago, from accretion to the first surviving rocks. The conditions inherited at the start of the Archean come from this earlier state.
Pilbara Craton: Archean craton in Western Australia preserving 3.5-billion-year-old dome-and-keel structures. A flagship terrane argued as evidence for vertical tectonics without plates.
Mantle viscosity: Archean mantle flowed more readily because higher temperature lowered its viscosity. Lower viscosity governs whether slabs can survive subduction or delaminate instead.
Great Oxidation Event: Rise of atmospheric oxygen around 2.4 billion years ago. Archean tectonic recycling and volcanism set trace gas conditions preceding oxygenation.
Dome-and-keel structures: granite-greenstone patterns where granitic domes alternate with synclinal greenstone keels. The characteristic Archean structure cited as evidence for vertical, not plate, deformation.
Protocrust: Earth's earliest solid crust, likely basaltic, mafic, and largely destroyed or reworked. Archean tectonics acted on and recycled this primitive crust.
Kaapvaal Craton: Southern African craton preserving 3.6-2.6-billion-year-old greenstone belts and granites. Its Barberton belt records early tectonic and hydrothermal activity in detail.
Slab pull: The force from a dense descending plate that largely drives modern plate motion. Hotter, weaker Archean slabs may have bent and broken rather than pulled plates.
Origin of life: Emergence of living systems, likely before 3.5 billion years ago. Hydrothermal settings supplied by Archean tectonics are leading candidates for life's cradle.

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