The fibration $\mathcal{F}_{t}$ has a multi-scale collapsing nature in the following sense: each fiber $\mathcal{F}_{t}^{-1}(v)$ with $v\in(-\frac{d_{1}}{d_{1}+d_{2}},\frac{d_{2}}{d_{1}+d_{2}})\subset\mathbb{I}$ has a further $S^{1}$-collapsing direction given by the fibration

$$S^{1}\to\mathcal{F}_{t}^{-1}(v)\xrightarrow{\pr_{v}}D$$

such that, as $t\to 0$, the collapsing rate of the $S^{1}$ fibers is of higher order than $\mathcal{F}_{t}^{-1}(v)$. This iterated collapsing in effect gives rise to various bubbles of different geometric natures. See Section 4.3 for detailed studies on the rescaled limit geometries.