  We investigate experimentally the quenching of a liquid pancake, obtained
through the impact of a water drop on a cold solid substrate ($0$ to
$-60^\circ$C). We show that, below a certain substrate temperature, fractures
appear on the frozen pancake and the crack patterns change from a 2D
fragmentation regime to a hierarchical fracture regime as the thermal shock is
stronger. The different regimes are discussed and the transition temperatures
are estimated through classical fracture scaling arguments. Finally, a phase
diagram presents how these regimes can be controlled by the drop impact
parameters.
