I agree with most reviews...even animalman's...gah!.

My take on him lifting the island was that after he recharged he picked up the island and a huge amount of earth (volcanic rock) underneath it, because by the time he got up to the atmosphere edge the falling rocks only then revealed the kryptonite and the island itself. So I'm assuming there were many iron and lead lined rocks that were somewhat protecting him to that point. after this he of course fell back to the Earth.