Tyndall Glacier flows generally south-southwest for 13 miles (21 km) to the head of Taan Fjord in Icy Bay, about 160 miles (258 km) east-southeast of Cordova and 68 miles (110 km) northwest of Yakutat, Alaska. The glacier starts at an elevation of about 10,000 feet (3,050 m) in the Saint Elias Mountains near the Canadian border, between Mount Huxley to the west and Mount Saint Elias to the east. Members of the New York Times Expedition named this tidewater glacier in 1886 for John Tyndall, a physicist and mountaineer who advanced understanding of the semi-fluid flow of glaciers. Taan Fjord lies in Wrangell-Saint Elias National Park and Preserve and extends about nine miles (15 km) from the eastern shore of Icy Bay. The fjord has been exposed over the past 50 years by Tyndall Glacier’s retreat and takes its name from the Tlingit word for “sea lion”. The bedrock surrounding Taan Fjord represents the Yakutat Terrane, one of seven terranes that formed near the equatorial Pacific Ocean and sequentially rafted northward on oceanic plates before accreting to North America. The Yakutat Terrane was the last to arrive, about 26 million years ago, and is still actively accreting to the continent. It consists of sedimentary rocks that accumulated as continental shelf deposits during the Eocene to Pleistocene epochs (roughly the last 50 million years), plus some oceanic volcanic rocks. The Chugach-Saint Elias Fault System and the Fairweather Fault separate it from the older terranes to the north.

Alaska currently has 50 glaciers that terminate in the ocean at either a grounded terminus or a floating ice tongue. These tidewater glaciers exhibit a repeating cycle: they advance slowly over centuries until thinning near the terminus triggers a rapid retreat that completes within decades, then stabilize only when retreating into shallow water. Climate changes can trigger the retreat phase, but once initiated, the glacier’s behavior is only weakly influenced by climate. Eight glaciers exist in Icy Bay; presently only five reach tidewater. These glaciers historically shared a common terminus extending into the Gulf of Alaska until the early 1900s. Since then the terminus has retreated and separated into smaller individual glaciers now up to 25 miles (40 km) from the gulf. Taan Fjord, one of Icy Bay’s four arms, was created when Tyndall Glacier separated from the glacier system after 1960. This glacier’s retreat occurred in three stages: the terminus retreated about 3.7 miles (6 km) between 1960 and 1969, then 1.2 miles (2 km) from 1969 to 1983, followed by another six miles (10 km) of retreat before stabilizing by 1996. The glacier’s rapid retreat destabilized the steep bedrock slopes of surrounding mountains, causing massive landslides.

Between 1983 and 1996 a large landslide occurred along the fjord wall near Tyndall Glacier’s toe. This landslide consisted of a slump that did not run far into Taan Fjord. On October 17th 2015, after heavy rains, a seismic event occurred at about 9:18pm local time: some 200 million metric tons of rock fell over 60 seconds from an escarpment on the north side of the Daisy Glacier valley. The force of this falling material remobilized the older slump debris, creating a high-speed landslide that entered Taan Fjord at Tyndall Glacier’s toe. The event generated a local mega-tsunami that sheared trees at an elevation of 500 feet (152 m) on a peninsula within the fjord. The wave was large enough to register at the nearest tidal gauge 96 miles (155 km) away. In 2016 another massive landslide occurred in Glacier Bay National Park. Such events happen perhaps three to five times a year around the world; south-east Alaska is the global hotspot. Read more here and here. Explore more of the Tyndall Glacier and Taan Fjord here: