Internal Suction that draws in from without. Internal Pressure that pushes out from within. External Suction that draws out from within. External Pressure that pushes in from without. Internal Suction draws substances of greater density toward and into a formation.
Internal pressure expands and gives shape and strength to the formation.
External Suction draws out gases from the formation. External Pressure pushes onto the formation and keeps it from bursting. To balance a formation, internal Suction must equalize external Suction, and internal Pressure must equalize external Pressure. In a growing formation internal Suction and Pressure are greater than external Suction and Pressure. In a formation in a state of decline, internal Suction and Pressure are lesser than external Suction and Pressure.