From Halopedia, the Halo wiki
Ridge spent his childhood on Mars,[note 1] and was friends with Cadmon and Thomas Lasky. Sometime around 2525-2526, he served with Cadmon on Arcadia. When his unit came upon a jungle river, Ridge warned the others not to drink the water because it was polluted; Cadmon ignored his friend's advice and contracted diarrhea, earning him the nickname "Volcano".
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