biostudies-literatureUnknown16(1)Zhao HCausal connections among major Ordovician environmental and biological events (i.e., long-term climatic cooling, Hirnantian Glaciation, Great Ordovician Biodiversification Event, and Late Ordovician Mass Extinction) remain in debate, and the hypothesis of volcanism-driven long-term cooling is untested. Here, we present both newly generated and compiled literature data for global volcanic activity (Hg geochemistry), sea-surface temperatures (conodont oxygen isotopes), and chemical weathering intensity (conodont strontium isotopes). This dataset documents a ~25-Myr-long interval of climatic cooling (~470-445 Ma), commencing around the onset of the Middle Ordovician, intensifying during the Late Ordovician, and ultimately culminating in the Hirnantian Glaciation. Cooling was associated with lNature communications11475https://www.ebi.ac.uk/biostudies/studies/S-EPMC12749037biostudies-literatureVolcanism and basalt weathering drove Ordovician climatic cooling.PMC12749037Algeo TJLyu ZHao FZhang LWang XZhao HfalseVolcanism and basalt weathering drove Ordovician climatic cooling.Causal connections among major Ordovician environmental and biological events (i.e., long-term climatic cooling, Hirnantian Glaciation, Great Ordovician Biodiversification Event, and Late Ordovician Mass Extinction) remain in debate, and the hypothesis of volcanism-driven long-term cooling is untested. Here, we present both newly generated and compiled literature data for global volcanic activity (Hg geochemistry), sea-surface temperatures (conodont oxygen isotopes), and chemical weathering intensity (conodont strontium isotopes). This dataset documents a ~25-Myr-long interval of climatic cooling (~470-445 Ma), commencing around the onset of the Middle Ordovician, intensifying during the Late Ordovician, and ultimately culminating in the Hirnantian Glaciation. Cooling was associated with l2025-01-01T00:00:00Z2025 Dec2026-07-15T07:00:19.827Z2026-06-30T03:36:16.083ZS-EPMC127490374138741110.1038/s41467-025-66316-4