  A large filament composed principally of two sections erupted sequentially in
the southern hemisphere on January 26 2016. The central, thick part of the
northern section was first lifted up and lead to the eruption of the full
filament. This event was observed in H-alpha with GONG and CLIMSO, and in
ultraviolet (UV) with the AIA/SDO imager. The aim of the paper is to relate the
photospheric motions below the filament and its environment to the eruption of
the filament. An analysis of the photospheric motions using SDO/HMI continuum
images with the coherent structure tracking (CST) algorithm developed to track
granules, as well as large-scale photospheric flows, has been performed. The
supergranule pattern is clearly visible outside the filament channel but
difficult to detect inside because the modulus of the vector velocity is
reduced in the filament channel, mainly in the magnetized areas. The horizontal
photospheric flows are strong on the west side of the filament channel and
oriented towards the filament. The ends of the filament sections are found in
areas of concentration of corks. Whirled flows are found locally around the
feet. The strong horizontal flows with an opposite direction to the
differential rotation create strong shear and convergence along the magnetic
polarity inversion line (PIL) in the filament channel. The filament has been
destabilized by the converging flows, which initiate an ascent of the middle
section of the filament until the filament reaches the critical height of the
torus instability inducing, consequently, the eruption. The "n" decay index
indicated an altitude of 60 Mm for the critical height. It is conjectured that
the convergence along the PIL is due to the large-scale size cells of
convection that transport the magnetic field to their borders.
