  We model the effects of repeated supernova explosions from starbursts in
dwarf galaxies on the interstellar medium of these galaxies, taking into
account the gravitational potential of their dominant dark matter haloes. We
explore supernova rates from one every 30,000 yr to one every 3 million yr,
equivalent to steady mechanical luminosities of L=0.1-10 x 10^38 ergs/s,
occurring in dwarf galaxies with gas masses M_g=10^6 - 10^9 solar masses. We
address in detail, both analytically and numerically, the following three
questions:
  1. When do the supernova ejecta blow out of the disk of the galaxy?
  2. When blowout occurs, what fraction of the interstellar gas is blown away,
escaping the potential of the galactic halo?
  3. What happens to the metals ejected from the massive stars of the
starburst? Are they retained or blown away?
  We give quantitative results for when blowout will or will not occur in
galaxies with 10^6 \leq M_g \leq 10^9 solar masses. Surprisingly, we find that
the mass ejection efficiency is very low for galaxies with mass M_g \geq 10^7
solar masses. Only galaxies with M_g \leq 10^6 solar masses have their
interstellar gas blown away, and then virtually independently of L. On the
other hand, metals from the supernova ejecta are accelerated to velocities
larger than the escape speed from the galaxy far more easily than the gas. We
find that for L_38=1, only about 30% of the metals are retained by a 10^9 solar
mass galaxy, and virtually none by smaller galaxies. We discuss the
implications of our results for the evolution, metallicity and observational
properties of dwarf galaxies.
