  We examine an external trigger mechanism that gives rise to the intense soft
gamma-ray repeater (SGR) giant flares. Out of the three giant flares, two
showcased the existence of a precursor, which we show to have had initiated the
main flare. We develop a reconnection model based on the hypothesis that
shearing motion of the footpoints causes the materialization of a Sweet-Parker
current layer in the magnetosphere. The thinning of this macroscopic layer due
to the development of an embedded super-hot turbulent current layer switches on
the impulsive Hall reconnection, which powers the giant flare. We show that the
thinning time is on the order of the pre-flare quiescent time.
