True that this earth was destroyed once by water but it will not be destroyed again by fire. According to Abraham, when Sodom and Gomorrah had to be destroyed, the Lord sent a revelation to Abraham to inform about His will. If you read Genesis 18:22-32, Abraham tried to bargain the salvation of Sodom and Gomorrah by playing so to speak with a number of "If's" all the way down from 50 righteous ones and until 10. The Lord allowed the bargain with Abraham down to a Minyan of 10 righteous male adult Jews. That's the number when the Lord would not allow to go any lower. If there was a Minyan of 10 righteous in Sodom and Gomorrah, the Lord would not destroy those cities. That's whence the Minyan of 10 Jews was inspired to start from. (Gen. 18:32)