  How does turbulence contribute to the formation and structure of the dense
interstellar medium (ISM)? Molecular clouds are dense, high-pressure objects.
It is usually argued that gravitational confinement causes the high pressures,
and that the clouds are (magneto)hydrostaticobjects supported by a balance
between magnetic and turbulent pressures and gravity. However, magnetic
pressures appear too weak, and MHD turbulent support not only requires driving,
but also results in continuing gravitational collapse, as has now been
demonstrated in simulations reaching 512^3 zones. Models of supernova-driven,
magnetized turbulence readily form transient, high-pressure, dense regions that
may form molecular clouds. They are contained not by self-gravity, but by
turbulent ram pressures from the larger flow. Apparent virialization may
actually be a geometrical effect. Turbulent clouds are unlikely to be in
hydrostatic equilibrium, instead either collapsing or expanding, although they
may appear well-fit by projected equilibrium Bonnor-Ebert spheres. Collapsing
clouds probably form stars efficiently, while expanding ones can still form
stars by turbulent compression, but rather inefficiently.
