The past tense of vanish off the face of the earth is vanished off the face of the earth.

The third-person singular simple present indicative form of vanish off the face of the earth is vanishes off the face of the earth.

The present participle of vanish off the face of the earth is vanishing off the face of the earth.

The past participle of vanish off the face of the earth is vanished off the face of the earth.