  Continuous observations were performed of a quiescent prominence with the
Solar Optical Telescope (SOT) on board the /emph{Hinode} satellite on 2006
December 23--24. A peculiar slowly-rising column of $/sim10^{4}$ K plasma
develops from the lower atmosphere during the observations. The apparent ascent
speed of the column is 2 km s$^{-1}$, while the fine structures of the column
exhibit much faster motion of up to 20 km s$^{-1}$. The column eventually
becomes a faint low-lying prominence. Associated with the appearance of the
column, an overlying coronal cavity seen in the X-ray and EUV moves upward at
$/sim$5 km s$^{-1}$. We discuss the relationship between these episodes, and
suggest that they are due to the emergence of a helical flux rope that
undergoes reconnection with lower coronal fields, possibly carrying material
into the coronal cavity. Under the assumption of the emerging flux scenario,
the lower velocity of 2 km s$^{-1}$ and the higher one of 20 km s$^{-1}$ in the
column are attributed to the rising motion of the emerging flux and to the
outflow driven by magnetic reconnection between the emerging flux and the
pre-existing coronal field, respectively. The present paper gives a coherent
explanation of the enigmatic phenomenon of the rising column with the emergence
of the helical rope, and its effect on the corona. We discuss the implications
that the emergence of such a helical rope has on the dynamo process in the
convection zone.
