1.At this point, the force throwing the volcanic material, or tephra, into the air diminishes, and it comes crashing down.

在这一点上，将火山物质或火山灰抛向空量减弱了，轰倒下。机翻

2.When it was over, almost 300 square kilometers were decimated, and Pompeii and Herculaneum lay under up to 65 feet of tephra.

当时，近 300 平方公里土地被摧毁，庞贝和赫库兰尼姆位于高达 65 英尺火山灰之下。机翻