Mammoth Springs Sentinels
Trees are a common casualty of the changing fortunes of Yellowstone's geothermal features. A particular area may lie dormant for decades, allowing plant life to flourish and trees to begin growing. Then, when that area begins to get active again, boiling mineralized water takes care of the trees in short order.
In this area near the higher elevations of Mammoth Hot Springs, several dead trees stand "watch" over the valley below. Ironically, the area has become mostly quiet again, and in time these trees may be replaced by live ones.