11 Menachem Av 5775
Considering what the Hebrew prophets reveal to us about earth changes at the End of Days (see Tanakh on Earth Changes), I think one possible cause of the prophesied destruction of two-thirds of the world could be a cataclysmic pole shift which could cause crustal displacement and a reversal of the earth's rotation after a close encounter with Planet X aka Nibiru.
Many lands will sink beneath the oceans while new land will emerge from the sea - pure and clean. The safest place to be will be Jerusalem which, as the place from which the whole earth was formed, will remain stationery: (Zekhariah 14.10-11) "The whole earth shall be changed to be like a plain, ...but it [Jerusalem] will be elevated high and remain in its old place.... and there shall be no more destruction; but Jerusalem shall dwell in safety." The closer one is to Jerusalem, the less the devastating effects will be felt.
(First 50 mins covers the whole topic)
(One view of what could happen during an Earth encounter with Nibiru.)