Despite alarms raised that adolescents' social media use can aggravate the harmful impact of residential risks (e.g. local violence) to their mental health, the mechanisms are poorly understood. To better understand potential mechanisms, we interviewed Latino adolescents living in a hypersegregated U.S. city, for whom social media may aggravate existing inequalities in residential risks to their mental health. Through an abductive analysis, we identified two processes suggesting how social media can amplify the deleterious impact of residential risks to their mental health. We refer to the first as additive, whereby social media heightens awareness of residential risks. The second is extension, whereby social media lengthens one's risk awareness, speeds up potential for risk awareness and multiplies who may become aware. We found evidence suggestive of parallel processes yielding diminution, whereby social media can minimise the deleterious effects of residential risks via adding and extending exposure to mental health resources, like collective efficacy. Further, the potential for extension (to both risks and resources) appears limited because social media practices (e.g. reposting, seeking viral attention) can foster indifference. Findings suggest the need to consider how adolescents activate resources via social media to avoid overstating its negative impact on mental health.