Many papers on meteorite impact suggest that large impacts can induce volcanic eruptions through decompression melting of the underlying rocks. We perform numerical simulations of the impact of an asteroid with a diameter of 20 km striking at 15 km·s−1 into a target with a near-surface temperature gradient of 13 K·km−1 (“cold” case) or 30 K·km−1 (“hot” case). The impact creates a 250–300-km-diameter crater with ∼10,000 km3 of impact melt. However, the crater collapses almost flat, and the pressure field returns almost to the initial lithostat. Even an impact this large cannot raise mantle material above the peridotite solidus by decompression. Statistical considerations also suggest that impacts cannot be the common initiator of large igneous provinces any time in post–heavy bombardment Earth history.