一堆雲

我對這幾句話大致的理解如下:
"最嚴重的一次是1992年當我是個15人座螺旋槳飛機機長時. 那是一趟25分鐘從Boston到Maine的飛行. 天氣炎熱的黃昏. 我看到了一堆塔狀的雲在NewEngland上方. 如同我看過最美麗的skyscape. 這些是因為不可見的火山噴發上升氣流所產生的"


"One of those severes took place in July 1992, when I was captain on a fifteen-passenger turboprop. It was, of all flights, a twenty-five-minute run from Boston to Portland, Maine. It had been a hot day, and by early evening, a forest of tightly packed cumulus towers stretched across eastern New England. The formations were short—about 8,000 feet at the tops, and deceptively pretty to look at. As the sun fell, it became one of the most picturesque skyscapes I’ve ever seen, with buildups in every direction forming a horizon-wide garden of pink coral columns. They were beautiful and, it turned out, quite violent—little volcanoes spewing out invisible updrafts. "


紅字是我一直沒辦法確定意思的地方
 of all flights:?

 It had been a hot day, and by early evening: 為什麼要用"had been"而不是用"was"?

 The formations were short—about 8,000 feet at the tops, and deceptively pretty to look at: 大致的理解是, "頂端大約都在8000尺,而且非常的吸引人" ,但前面的 "The formations were short"一直看不懂是什麼意思,硬翻就是"隊形是短的"....

 buildups in every direction forming a horizon-wide garden of pink coral columns: 這段先跳過去@@...

They were beautiful and, it turned out, quite violent—little volcanoes spewing out invisible updrafts:
感覺每個字都看得懂,但就不知道他怎麼組合的,看不出這句子的結構
They were beautiful: 那是漂亮的(指那堆雲)
 it turned out :險露出 
quite violent :很強,很嚴重
little volcanoes spewing out invisible updrafts :一座小火山噴發出不可見上升氣球.