Jackpot Bay is a fjord on the Kenai Peninsula that extends west for 6.5 miles (10.5 km) from Dangerous Passage, about 43 miles (69 km) northeast of Seward and 34 miles (55 km) southeast of Whittier, Alaska. Fishermen used the name locally, and it was reported in 1897 by Lieutenant Commander Jefferson F. Moser of the U.S. Navy, who commanded the U.S. Fish Commission steamer Albatross and led fisheries surveys and investigations in western Prince William Sound from 1897 to 1901.
The alluvial fan at the base of the waterfall is an accumulation of sediment eroded from the steep, deglaciated slope above. Alluvial fans typically form where a confined feeder channel exits a mountain front or glacier margin; as the flow leaves the channel and spreads across the fan surface, its carrying power drops, causing suspended sediment to settle out. Fans range in area from less than 1 acre (0.4 ha) to thousands of square miles. In deglaciated fjords, post-glacial rebound gradually lifts these sediment deposits above sea level, letting terrestrial vegetation colonize the emerging fans. Prince William Sound’s fjords, flanked by steep slopes and supplied with sediment of highly variable grain size, are prone to submarine landslides and sediment flows.
On March 27, 1964, the magnitude 9.2 Great Alaska earthquake triggered localized tsunamis in several fjords, straits, and bays across Prince William Sound. In Dangerous Passage, a tsunami devastated the village of Old Chenega, killing 23 of its 75 residents, the highest proportional loss suffered by any community in the disaster. In 2014, the U.S. Geological Survey conducted a high-resolution bathymetric survey of the area and found widespread evidence of seafloor change from slope failure and landslide generation. The results indicate that a large, unstable accumulation of sediment on the fjord’s slope collapsed catastrophically during the earthquake, generating the tsunami that struck Chenega roughly four minutes later. Read more here and here. Explore more of Jackpot Bay and Dangerous Passage here: