1. The researchers discovered a new type of rock formation that is believed to be volcanogenic in origin.
研究人员发现了一种新型的岩石形成，据信是由火山活动引起的。
2. The volcanogenic gases emitted by the erupting volcano posed a threat to the nearby communities.
喷发的火山引发的火山气体对附近社区构成了威胁。