And the spot where the gravity readings are especially high ... this is right in the middle of a 500-kilometer wide circular ridge, what could be part of an old impact crater. And if there was an asteriod impact there in Wilkes Land, the next question is: did it happen 250 million years ago? Because that would put it when in geologic history?

我查了一下，这是“托福听力题”，这段文字估计是根据音频整理的。里面确实存在一些错误：

And the spot where the gravity readings are especially high ... （这里是省略号，说明前文没有结束）this is right in the middle of a 500-kilometer wide, circular ridge, what （莫名其妙：what引导疑问句却没有问号；引导名词性从句却不知作何种成分）could be part of an old impact crater.

And if there was an asteroid impact there in Wilkes Land, the next question is: did it happen 250 million years ago? Because that would put it when in geologic history?（状语从句不能单独成句；此外，问号不知缘何而来？）

建议：既然有这些错误，而且找不到原听力材料，就不必纠结此问题了。