New Defender's Study Bible Notes
7:11 seventeenth day. The exact date of the Flood’s onset must have been noted for some reason. The ark landed on the mountains of Ararat exactly 150 days or five months later (see Genesis 8:3,4). The implication is that the primeval year contained twelve months of thirty days each (see also Revelation 11:2, 3).
7:11 fountains of the great deep. The physical cause of the Flood is clearly identified as the eruption of the waters in the “great deep” and the opening of the floodgates of heaven. These are quite sufficient in themselves to cause and explain all the phenomena of the Flood. The antediluvian hydrologic cycle was apparently controlled by a system of subterranean pressurized reservoirs and conduits, but these fountains were all cleaved open in one day, releasing tremendous quantities of water and magma to the earth’s surface and dust and gas into the atmosphere. The resulting combination of atmospheric turbulence and dust nuclei of condensation was probably the immediate cause of the precipitation of the vapor canopy. The cataclysmic restoration of the primeval deep that resulted left the antediluvian world completely devastated and inundated.