  We investigate the kinematic-chemical distribution of Red Giant Branch (RGB)
stars from the LAMOST survey crossed matched with Gaia DR2 proper motions, and
present time tagging for the well-known ridge structures (diagonal
distributions for $V_R$ in the $R$, $V_\phi$ plane) in the range of
Galactocentric distance $R$ = 8 to 15 kpc. We detect six ridge structures,
including five ridges apparent in the radial velocity distribution and three
ridges apparent in the vertical velocity, the sensitive time of which to the
perturbations are from young population (0$-$3 Gyr) to old population (9$-$14
Gyr). Based on an analysis of the evolution of angular momentum distribution,
we find that four ridges are relatively stationary, while another is evolving
with time, which is confirmed by the difference analysis at different
populations and supporting that there might be two kinds of dynamical origins.
Furthermore, ridge features are also vividly present in the chemical properties
([Fe/H], [$\alpha$/Fe]). The comparison between the north and south hemispheres
of the Galaxy does show some differences and the ridge features are
asymmetrical. Moreover, we find that diagonal ridge structures may affect the
shape of the rotation curve, which is manifested as fluctuations and
undulations on top of a smooth profile. Finally we speculate that the bar
dynamics should be not enough to explain all ridge properties including the
break feature in the $V_Z$-$L_Z$ plane.
