Throughout Earth history, extensive, sub-aerial, basaltic lava flows associated with continental rifting and hot spots have been contemporaneous with major global warming—the more extensive the flows, the longer the period of eruption, and the greater the warming of air and oceans. Around 251 Ma, basalts covered an area in Siberia of 5 million km2 probably within 670,000 years, causing equatorial oceans to become highly acidic with temperatures >40°C. Approximately 96% of all marine species and 70% of all terrestrial vertebrate species went extinct in an environmental crisis mapped globally as the end of the Paleozoic. The Deccan basalts covered an area of 0.5 million km2 around 66 Ma causing warming and extinctions that formed the end of the Mesozoic. Around 56 Ma, rifting of Norway from Greenland extruded as much basalt as 3000 km3 per km of rift per million years, forming the Paleocene Eocene Thermal Maximum. Hundreds of smaller basalt eruptions punctuate the geologic time scale ending geologic eras, periods, epochs, and even ages. In historic time, the Great Þjórsá Lava, covering 970 km2 of Iceland, led to major warming around 8600 BP. The King’s Bowl and Wapi lava fields covered 700 km2 of the Snake River Plain in southern Idaho around 2250 BP during the Roman Warm Period. The basaltic volcano Eldgjá covered 800 km2 of Iceland around 939 AD, associated with the Medieval Warm Period. The much smaller volcano Bárðarbunga erupted 85 km2 of basalt in 6 months starting in 2014, the largest basalt flow since 1783, contemporaneous with sudden warming in the northern hemisphere of 0.47oC from 2014 to 2016. The rate of flood-basalt areal coverage was 0.5 km2 per day. The Kona eruption has been extruding basalts covering 0.6 to 0.4 km2 per day from May 3 through July 27. If this eruption continues for 6 months, it could affect climate as much as Bárðarbunga. Warming appears caused by ozone depletion, allowing more UV-B than usual to reach Earth. UV-B radiation is hot enough to burn skin and is 48 times hotter than infrared radiation absorbed strongly by CO2. Basaltic eruptions emit especially high volumes of chlorine and bromine, which are observed to cause ozone depletion. The exact chemical path is not yet well understood. Heat waves during the summer of 2018 are associated with a “sharply kinked” jet stream often thought caused by ozone depletion.