They have made the cave shudder again, all night, a fast heartbeat pounding up through my flank, boom and boom and boom, faster than any beat I know. My beats are the freeze and the thaw, the slow crack that opens a hairline over ten thousand summers. Theirs is quicker. Theirs will be over before the moss on my north side has finished drinking one rain.
Inside the hollow the soft quick creatures gather in the dark and warm each other by moving. Hundreds of them, packed close, giving off heat the way a sunlit slope gives off heat, all pointed one direction, all trembling in the same rhythm, as though a single tremor ran through the whole herd at once.
I have felt herds before. Mammoths passed over me once, a thick warm weight, and then a colder weight, and then nothing for a very long time. These are lighter and they last less.
They do this until the sky pales, then they scatter and are gone, blinking, slow now, the heat draining out of them into the morning cold. The hollow sits empty. I understand emptiness. I was here before the hollow was dug and I will be here after it fills back in.
I do not know what they were fleeing or what they were reaching, only that the flee and the reach were the same and lasted a night. Tonight another herd will come and shudder in the same dark for the same little while. Something soft is always arriving to be warm and always leaving before it is warm enough. It is a pleasant enough disturbance.
I will have forgotten it long before the next glacier.