In this paper a new type of crisis in random maps is studied. The trigger of this new crisis is the tunnel effect induced by a backward tangent bifurcation. This is different from the formerly reported crises caused by the collision of the chaotic attractor with an unstable orbit. The reasons why the characteristic time of this new crisis is super long are given. Another case of crisis triggered by the random collision of the attractor with the system's trapping region boundary can also be found in this model. The two cases of crisis can transform into each other by continuously varying the control parameter.