Predator's Gold (Mortal Engines #2) | Philip Reeve

The Jenny was drifting across the shoulder of a big volcano. Beyond it there were no more mountains, just an endless blue-white plain stretching to the horizon. They were at the mercy of the wind, and it was carrying them helplessly into the Ice Wastes. Tom and Hester, now in possession of the airship Jenny Haniver, find themselves being pursued by League forces. Scrambling to escape, they head north and land on the city of Anchorage. But the savage Huntsmen of Arkangel are closing in, and the young margravine must make a last desperate bid for survival.