The law of superposition states:
rock layers closest to the bottom are the newest
rock layers closest to the surface are the newest
rock layer vertical placement has no bearing on the layer's age

Some gamma ray bursts are hypothesized to come from mergers of neutron stars or black holes. if this hypothesis is correct, what else should we in principle be able to detect from such mergers? a. gravitiational waves b. x-ray bursts c. significant disruption of gas thousands of light-years away in the surrounding galaxy d. an "afterglow" of bright visible light, lasting for weeks