Diatremes are carrot-shaped bodies forming the upper parts of very deep magmatic intrusions of kimberlite rock. These unusual, enigmatic and complex features are famous as the source of diamonds. Here we present a new model of kimberlite ascent and eruption, emphasizing the extremely unsteady nature of this process to resolve many of the seemingly contradictory characteristics of kimberlites and diatremes. Dyke initiation in a deep CO2-rich source region in the mantle leads to rapid propagation of the dyke tip, below which CO2 fluid collects, with a zone of magmatic foam beneath. When the tip breaks the surface of the ground, gas release causes a depressurization wave to travel into the magma. This wave implodes the dyke walls, fragments the magma, and creates a `ringing' fluidization wave. Together, these processes form the diatreme. Catastrophic magma chilling seals the dyke. No precursor to the eruption is felt at the surface and the processes are complete in about an hour.