It is shown that the H I shells and supershells, recently reported by Heiles, are a natural byproduct of the interaction of the stellar winds and supernovae, originating from stars in typical OB associations, with the surrounding interstellar medium. The validity of this model is supported by its ability to reproduce observed characteristics of the shells such as the shell sizes and shapes as a function of their distances from the galactic center. This process may also be responsible for injecting synthesized elements into the galactic halo.
Bruhweiler, C., Gull, T.R., Kafatos, M., Sofia, S. (1980) Stellar Winds, Supernovae, and the Origin of the H I A supershells, Astrophysical Journal, 238: L27-L30. doi: 10.1086/183250