Marvel Two-in-One (1974 1st Series) #16

"Into the Savage Land!" Guest-starring Ka-Zar. Fantastic Four cameo. To prevent a natural catastrophe from destroying life on Earth as we know it, Mr. Fantastic has sent Ben Grimm to Antarctica, and more specific the Savage Land, to investigate. But when Thing and his pal Ka-Zar, the Lord of the Hidden Jungle, discover the cause of these eruptions they find the catastrophe may not be as natural as they at first thought