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We appreciate the comment by A.Y. Glikson on our paper ([Ivanov and Melosh, 2003a][1]). He raises, we believe, five major points, to which we reply below: 1. Glikson suggests that the eruption of the Deccan traps at the Cretaceous-Tertiary (K-T) boundary is a possible exception to the lack of

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.

The sequence of events subsequent to the impact of a large meteoroid in an ocean differs in several respects from an impact on land. Even if the meteoroid is large enough to produce a crater on the sea floor (that is, larger than a few km in diameter), the presence of water affects the character of the early-time events. The principal difference between land and oceanic impacts is the expansion of shock-vaporized water following an oceanic impact. A steam explosion follows the meteoroid's deposition of energy in the target. Shocked water expands from an initial pressure of 3 to 6 Mbar for 20-30 km/second impacts, ejecting water vapor and dust from the vaporized meteoroid several hundred km into the atmosphere. The violent vapor plume thus formed may explain how dust with a dominantly meteoritic composition can be dispersed to form a world-wide dust layer, as required by the Alvarez hypothesis.

The recent discovery of ALHA81005, a small meteorite that undoubtedly came from the moon, has raised questions about how an intact rock fragment could survive acceleration to planetary escape velocities. This acceleration could only have been produced by a large impact on the lunar surface. A small amount of material (0.005 to 0.02 projectile volume) may be ejected from an impact crater at speeds exceeding lunar escape velocity without suffering petrographically detectable shock damage. The ejected material is protected by stress-wave interference close to the free surface. The existence and size of this zone depend upon parameters such as the rise time of the stress pulse produced by an impact. The fragment size is a function of ejection velocity. The lunar meteorite was ejected during an impact event that produced a crater at least 3.6 km in diameter. Other meteorites may have originated in a similar way.