  We consider a forming galaxy undergoing multitudinous supernova (SN)
explosions, as a possible model of \lya blobs (LABs). For this purpose, an
ultra--high resolution hydrodynamic simulation is performed using $1024^3$ grid
points, where SN remnants are resolved with sufficient accuracy. It is found
that multiple SN explosions produce kpc--size expanding hot bubbles, which
drive cool, dense shells by strong shock. The colliding high--density cooling
shells radiate intensive \lya emission, resulting in a high \lya luminosity of
$\sim10^{43}$ erg s$^{-1}$, comparable to the observed level in LABs. Also,
recently discovered bubbly features in some LABs are quite similar to the
structure predicted in the present simulation. Furthermore, the result
demonstrates that LABs are representative of evolving primordial galaxies; they
could hold direct information on the early chemical enrichment of galaxies,
contrary to present--day galaxies which have undergone intense recycling of
interstellar matter, thus erasing most of the early chemical history. It turns
out that the metal mixing proceeds in a very inhomogeneous fashion, so that
there appears a large spread of metallicity, that is,$[{\rm Fe/H}] \approx 0
{\rm ~to} -5$ or $[{\rm O/H}] \approx 1 {\rm ~to} -4$. Hence, the early
galactic chemical evolution may have proceeded in a different manner from that
hitherto considered in one--zone models.
