The electrical arc erosion behavior extremely limits the lifespan of electromechanical switching devices. Observation of the gradual evolution of arc erosion is highly beneficial for to understand the arc ignition and the contact degradation. In this article, the erosion of contact materials is simulated and visualized in situ with the recorded 2-D microscopic images. A novel method for erosion area identification is proposed with the combination of difference image method and mathematical morphology operations. The variation in erosion area as a function of switching current cycles is demonstrated, and the center of erosion zone that migrates continuously during the endurance experiment is determined. Finally, not only three types of arc erosion regimes (centralized arc erosion, separated arc erosion, and commutated arc erosion) are revealed, but also the associated occurrence probabilities during 1000 cycles are provided.