Icy Bay (

Tlingit The Tlingit or Lingít ( ) are Indigenous peoples of the Pacific Northwest Coast of North America. , they constitute two of the 231 federally recognized List of Alaska Native tribal entities, Tribes of Alaska. Most Tlingit are Alaska Natives; ...

: ''Lig̲aasi Áa'') is a body of water in the borough of Yakutat,

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

, formed in the last 100 years by the rapid retreat of the

Guyot In marine geology, a guyot (), also called a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than below the surface of the sea. The diameters of these flat summits can exceed . Guyots are most commonly fo ...

, Yahtse, and Tyndall

Glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

s. It is part of the Wrangell-Saint Elias Wilderness. At the beginning of the 20th century, the bay entrance was permanently blocked by a giant

tidewater glacier The tidewater glacier cycle is the typically centuries-long behavior of tidewater glaciers that consists of recurring periods of advance alternating with rapid retreat and punctuated by periods of stability. During portions of its cycle, a tidewat ...

face that calved

iceberg An iceberg is a piece of fresh water ice more than long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an i ...

s directly into the

Gulf of Alaska The Gulf of Alaska ( Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the ...

. A century-long

glacial retreat The retreat of glaciers since 1850 is a well-documented effect of climate change. The retreat of mountain glaciers provides evidence for the rise in global temperatures since the late 19th century. Examples include mountain glaciers in western ...

has opened a multi-armed

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a ''gulf'', ''sea'', ''sound'', or ''bight''. A ''cove'' is a small, ci ...

more than long. Icy Bay is a popular destination for

sea kayak A sea kayak or touring kayak is a kayak used for the sport of Watercraft paddling, paddling on open waters of lakes, bays, and oceans. Sea kayaks are seaworthy small boats with a covered deck and the ability to incorporate a spray deck. They t ...

ers, and is reachable by

bush plane A bush plane is a general aviation aircraft used to provide both scheduled and unscheduled passenger and flight services to remote, undeveloped areas, such as the Canadian north or bush, Alaskan tundra, the African bush, or savanna, Amazon rainf ...

from Yakutat,

2015 landslide and megatsunami

At 8:19 p.m.

Alaska Daylight Time The Alaska Time Zone observes standard time by subtracting nine hours from Coordinated Universal Time ( UTC−09:00). During daylight saving time its time offset is eight hours ( UTC−08:00). The clock time in this zone is based on mean sola ...

on October 17, 2015, the side of a mountain collapsed on the western end of the head of Taan Fiord, a finger of Icy Bay formed by the retreat of Tyndall Glacier. The resulting

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

generated a

megatsunami A megatsunami is an incredibly large wave created by a substantial and sudden displacement of material into a body of water. Megatsunamis have different features from ordinary tsunamis. Ordinary tsunamis are caused by underwater tectonic activi ...

in Taan Fjord. The area is uninhabited and no one was visiting it at the time, and the event went undetected for several hours until its signature was noted as a 4.9

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

event on

seismogram A seismogram is a graph output by a seismograph. It is a record of the ground motion at a measuring station as a function of time. Seismograms typically record motions in three cartesian axes (x, y, and z), with the z axis perpendicular to the ...

s at

Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...

New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...

. Scientists visited the

fjord In physical geography, a fjord (also spelled fiord in New Zealand English; ) is a long, narrow sea inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Antarctica, the Arctic, and surrounding landmasses of the n ...

in the spring and summer of 2016 to gather data on the event. Their studies revealed that the landslide consisted of about of rock with a volume of and lasted 60 to 100 seconds, reaching a maximum speed of . Some of the landslide came to rest on the foot of Tyndall Glacier, but about of rock with a volume of about entered the fjord, where it dislodged another of material from the bottom of the fjord. Some of the landslide's debris traversed the water at the head of the fjord and then climbed to reach a final resting place at an elevation of about on the opposite shore. Altogether, the landslide debris covered . The landslide generated a megatsunami with an initial height of about that struck the opposite shore of the fjord, with a run-up height (i.e., the maximum height on land the megatsunami reached as it ran up the shore) of . At a speed of up to , the megatsunami then continued down the entire length of the fjord – about – and into Icy Bay. In the uppermost of the fjord, run-up exceeded along the shore, and run-up heights in the upper part of the fjord otherwise varied between on the southeast shore and on the northwest side. In the middle part of the fjord, run-up heights varied greatly, dropping to as low as in some places but reaching in others. In the lower fjord, run-up heights on both sides were , increasing to at the entrance to the fjord. Along its path, the wave inundated an overall area of and left a trim line at its run-up height, stripping away all vegetation, including

alder Alders are trees of the genus ''Alnus'' in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species ex ...

forests, and leaving behind barren beaches that reached elevations of . The wave may have been about tall when it entered Icy Bay itself about 12 minutes after the landslide, and it inundated the bay's coastline with run-up levels of as much as in some places, although the run-up diminished to below the normal high-tide level in Icy Bay at distances greater than from the mouth of Taan Fiord. When it reached the nearest

tide gauge A tide gauge is a device for measuring the change in sea level relative to a vertical datum. It is also known as a mareograph, marigraph, and sea-level recorder. When applied to freshwater continental water body, water bodies, the instrument may ...

, located to the southeast of the landslide near Yakutat, Alaska, the wave had diminished to a height of . The Taan Fiord event bore a strong similarity to the July 1958 landslide and megatsunami in Alaska's

Lituya Bay Lituya Bay (; Tlingit language, Tlingit: ''Ltu.aa'',. Spelled L'tua in translation of Tebenkov's log. meaning 'lake within the point') is a fjord located on the coast of the south-east part of the U.S. state of Alaska. It is long and wide at ...

. The Taan Fiord landslide was the largest recorded in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

since the eruption of Mount St. Helens in May 1980, and the largest non-volcanic landslide in North America ever recorded. The megatsunami was the largest known marine tsunami worldwide since the Lituya Bay wave; although the Taan Fiord landslide was larger than the one at Lituya Bay, the Lituya Bay wave was larger than the one in Taan Fiord because the landslide in Taan Fiord did not fall from as great a height and landed in shallower water. The Taan Fiord wave also was the fourth-largest megatsunami of any type over the previous 100 years, with the fourth-highest run-up ever recorded anywhere in the world. Scientists assessed the landslide occurred because the retreat of Tyndall Glacier between 1961 and 1991 had left the mountainside unsupported by what had once been about of glacial ice. They also noted that heavy rains may have weakened the mountainside further, and that seismic waves from a 4.1-magnitude

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

centered about away arrived two minutes before the landside began and may also have contributed to the event.

References

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External links

Sea Kayaking in Icy BayIcy Bay Mega Tsunami (Alaska National Parks video) on YouTube
Fjords of Alaska Bodies of water of Yakutat City and Borough, Alaska Tourist attractions in Yakutat City and Borough, Alaska Megatsunamis