Mount Adams was last active about 1,000 years ago and has created few eruptions during the past several thousand years, resulting in several major lava flows, the most notable being the A. G. Aiken Lava Bed, the Muddy Fork Lava Flows, and the Takh Takh Lava Flow. One of the most recent flows issued from South Butte created the long by wide A.G. Aiken Lava Bed. Thermal anomalies (hot spots) and gas emissions (including hydrogen sulfide) have occurred especially on the summit plateau since the Great Slide of 1921.