yagog and magog are alive but invisible to us even with the tech that take pictures from up above will never be able to pick them up until Allah (god almighty)allows them to come out and you dont want to be alive at that time they are going to destroy and eat everything only Allah (god almighty) will know how to destroy them.
may Allah (god almighty) help those who happen to be at that time to see yagog and magog believe me you dont want to see them.
for more info go look at the quran and the saqyings of the prophet Muhammed (pbuh).