From Beyond Space and Time 2 — H.G. Wells

Scientists, military, archeologists, hunters, and treasure explorers uncover a lost world of Jurassic dinosaurs, and what they think are unknown early or last dinosaur species, with other strange life forms, trapped in an immense crater, surrounded by immense cliffs, at the center of an uncharted Pacific island, and start to uncover a colossal fifteen-mile flying saucer buried beneath the island!A new military aerial detection system is being tested for the first time on a plane in the Pacific and an uncharted island appears and it detects something of unknown origins at the island just before the plane stops working and crashes.They discover a lost world of Jurassic monsters and what they start to believe are unknown early or last dinosaur species, with other strange life forms, believed to be mutants or early forms of dinosaurs, trapped in the immense crater, surrounded by immense cliffs, at the center of the island.After they leave the island, they soon return to the island with hunters and start capturing them, and they explore the cavity trying to determine what it is, and start to uncover the colossal fifteen-mile flying saucer buried under the ground, with the monstrous extraterrestrial entity inside, waiting to be revived, with powers capable of destroying the galaxy.