Names for an Obstacle

This iceberg of granite
with its heft underground
lodges in my field and dooms
my way. It won’t budge for chains,
stone hammers or dynamite, so
I go around it with my plow and
no crops grow where it lies,
this glacial snag, dotted with
bird stains, circled by weeds,
seamed with scars, this exile
from time, ancient as grief,
a tusk thrust from the depths
of earth’s ocean.