In 3rd Nephi chapter 9, Mormon has just written about the natural disasters at the death of Christ and is (as usual) eager to point out the fulfillment of prophecy.
14 And now, whoso readeth, let him understand; he that hath the scriptures, let him search them, and see and behold if all these deaths and destructions by fire, and by smoke, and by tempests, and by whirlwinds, and by the opening of the earth to receive them, and all these things are not unto the fulfilling of the prophecies of many of the holy prophets.
Which holy prophets? In verse 16, he says that
Zenos did testify of these things
When we compare with 1st Nephi 19:11-12, we realize that Zenos indeed did testify of these things and that Nephi even quoted it
11 For thus spake the prophet: The Lord God surely shall visit all the house of Israel at that day, some with his voice, because of their righteousness, unto their great joy and salvation, and others with the thunderings and the lightnings of his power, by tempest, by fire, and by smoke, and vapor of darkness, and by the opening of the earth, and by mountains which shall be carried up. 12 And all these things must surely come, saith the prophet Zenos
This is another example of internal consistency in the Book of Mormon. Some of it so subtle that you don't discover it until you read it for the 30th time.