The subaerial expression of the Mid-Atlantic Ridge on Iceland comprise
s two overlapping spreading axes, referred to as the West Volcanic Zon
e (WVZ) and the East Volcanic Zone (EVZ), respectively. The way the sp
reading rate is distributed on both volcanic zones has an important im
pact on the stress pattern in the overlap area. Our field data from th
e area trace the evolution of the stress direction as recorded by slip
motion on fault planes. We found four different strike-slip stress ph
ases. An early N-S compression phase (A) preceded a NE-SW compression
phase (B). This phase was followed by a SE-NW compression phase (C). H
owever, we cannot date an E-W compression, phase (D), relative to the
other phases. Numerical modeling based on the assumption that the WVZ
has been permanently active during the last 3 Myr and that the EVZ is
propagating southward confirms that stress directions have rotated clo
ckwise by more than 140 degrees. These results fit perfectly with our
field analysis, and we propose that phase A corresponds to initial EVZ
ridge-tip propagation, phase B to emplacement of the EVZ southern tip
near Torfajokull, and phase C to an extreme southern location near th
e Surtsey Islands of the EVZ southern tip. Phase D could correspond to
an intermediate stage between phases B and C. We suggest that this se
quence of tectonics, recorded in a regional overlapping ridge-tip sett
ing, is directly analogous to smaller-scale and more common phenomena
at second-order ridge discontinuities throughout the global mid-ocean
ridge system.