在亚利桑那州中北部的弗拉格斯塔夫附近是日落火山口火山国家纪念碑，它保留了旧金山火山场中最年轻，最不受侵蚀的600个锥体的锥形锥体，提醒着科罗拉多高原最近的火山喷发。 景观中的数百个火山特征是由公元1085年左右发生的一系列火山爆发造成的，并且由居住在这里的美洲原住民部落见证。 公园的大部分表面都被熔岩流或深火山灰沉积物覆盖，被松树和白杨树的小岛屿，沙漠灌木和其他公园恢复生机的证据所破坏。 诸如Penstemon clutei（Sunset Crater penstemon）和Phacelia serrata（锯phacelia）等植物是仅在旧金山火山场内的煤渣沉积物中发现的短寿命野花。 这些为在干旱环境中查看和研究喷发动态，变化和恢复提供了独特的机会。
英国杜伦大学地质Assignment代写：火山灰沉积
Near the Flagstaff in north-central Arizona is the Sunset Crater Volcano National Monument, which retains the youngest, most eroded 600 cone conical cones in the San Francisco volcanic field, reminding the Colorado Plateau The most recent volcanic eruption. Hundreds of volcanic features in the landscape were caused by a series of volcanic eruptions that occurred around 1085 AD and were witnessed by Native American tribes living here. Most of the park’s surface is covered by lava flows or deep volcanic ash deposits, and is destroyed by evidence of small islands of pine and poplar trees, desert shrubs and other parks. Plants such as Penstemon clutei (Sunset Crater penstemon) and Phacelia serrata (saw phacelia) are short-lived wildflowers found only in cinder deposits in the San Francisco volcanic field. These provide unique opportunities to view and study eruption dynamics, changes and recovery in arid environments.