Mt. Fuji, Japan's highest peak and an active volcano, serves multiple scientific roles: monitoring air pollution, hosting cosmic-ray and lightning observations, supporting high-altitude medicine and training, and providing a natural laboratory for studies in extreme and alpine environments. Its societal importance is equally urgent. Located near Tokyo and other populated regions, an eruption would cause social and economic impacts. Assessing hazards such as ash, lava flows, pyroclastic flows, volcanic gas, and lahars is vital for disaster preparedness, while monitoring data aid evacuation and infrastructure protection. Similar opportunities and challenges exist at other high-altitude mountains and active volcanoes worldwide. We therefore propose viewing them collectively as a virtual, distributed laboratory-a "collaboratory," in the sense of a center without walls where researchers collaborate and share resources and data regardless of geography. This session invites contributions on extreme and alpine environments and volcanic hazards, aiming to share insights and build an international collaboratory.

Mt. Fuji, Japan's highest peak and an active volcano, serves multiple scientific roles: monitoring air pollution, hosting cosmic-ray and lightning observations, supporting high-altitude medicine and training, and providing a natural laboratory for studies in extreme and alpine environments. Its societal importance is equally urgent. Located near Tokyo and other populated regions, an eruption would cause social and economic impacts. Assessing hazards such as ash, lava flows, pyroclastic flows, volcanic gas, and lahars is vital for disaster preparedness, while monitoring data aid evacuation and infrastructure protection. Similar opportunities and challenges exist at other high-altitude mountains and active volcanoes worldwide. We therefore propose viewing them collectively as a virtual, distributed laboratory-a "collaboratory," in the sense of a center without walls where researchers collaborate and share resources and data regardless of geography. This session invites contributions on extreme and alpine environments and volcanic hazards, aiming to share insights and build an international collaboratory.