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，将物质灰抛向空中力量减弱了，它轰倒下。

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

当它结束时，近 300 平方土地被摧毁，庞贝和赫库兰尼姆位于高达 65 英尺灰之下。