During the 1964 Alaska earthquake , areas around the head of Turnagain Arm near Girdwood and Portage dropped as much as by subsidence and subsequent tidal action . Both hamlets were destroyed . Girdwood was later relocated inland and Portage was abandoned . About of the Seward Highway sank below the high-water mark of Turnagain Arm ; the highway and its bridges were raised and rebuilt in 1964 – 66
1964 Alaska earthquake
1964 Alaska earthquake
Cook Inlet