  We argue that the North Polar Spur (NPS) and many less prominent structures
are formed by gaseous metal-rich plumes associated with star-forming regions
(SFRs). The SFRs located at the tangent to the 3-5 kpc rings might be
particularly relevant to NPS. A multi-temperature mixture of gaseous components
and cosmic rays rises above the Galactic disk under the action of their initial
momentum and buoyancy. Eventually, the plume velocity becomes equal to that of
the ambient gas, which rotates with different angular speed than the stars in
the disk. As a result, the plumes acquire characteristic bent shapes. An ad hoc
model of plumes' trajectories shows an interesting resemblance to the
morphology of structures seen in the radio continuum and X-rays.
