  We analyze the dynamics of M-theory on a manifold of G_2 holonomy that is
developing a conical singularity. The known cases involve a cone on CP^3, where
we argue that the dynamics involves restoration of a global symmetry,
SU(3)/U(1)^2, where we argue that there are phase transitions among three
possible branches corresponding to three classical spacetimes, and S^3 x S^3
and its quotients, where we recover and extend previous results about smooth
continuations between different spacetimes and relations to four-dimensional
gauge theory.
