Blue Hole (Red Sea)
The Blue Hole is a diving location on the southeast Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.
Blue Hills (Washington)
The Blue Hills are perched on the north edge of the Seattle uplift, an east-west trending syncline or arch between the Seattle Fault and Tacoma fault formed by north-south compression of the bedrock. (See Puget Sound faults#Geological setting.)
Sharp downwarping of these formations has created numerous faults, including the dip-slip (vertical movement) Gold Creek fault that separates the two mountains. Strands of the Seattle fault, which east of here trend nearly due west-east, appear to turn to the southwest in the vicinity of Green Mountain.