  Barry Arm | |
| Location | Prince William Sound, Alaska, United States |
|---|---|
| Type | Landslide |
The Barry Arm landslide is an ongoing landslide in the Barry Arm fjord, northeast of Whittier, Alaska. The landslide is currently sliding into the waters of the fjord. Recently discovered in 2020, scientists fear that the slope may trigger a large tsunami when it falls into the fjord. [1]
The Barry Arm landslide measures about 650,000,000 cu yd (500,000,000 m3). It existed as far back as in the 1920s based on photographic evidence. From May 2010 to September 2013, during the retreat of Barry Glacier, the landslide moved at 85 ± 9 ft (25.9 ± 2.7 m) per year. The rate decreased to 4.25 ± 2.3 ft (1.30 ± 0.70 m) per year in March 2017 when the recession stopped. [2]
Satellite data and imagery indicate the large part of the landslide directly above the fjord waters began sliding on August 23, 2022. The slide is currently moving at a rate of 1.6–2.7 in (41–69 mm) each day. However, the volume of the landslide remains undetermined because the depth is uncertain. Similar movement were recorded since 2008 and 2020. However, the recent movement is at least twice as fast and occurring over a greater area. [2] The landslide consists of four parts (north to south: Tail, Core, Prow, Kite). In September 2022, movement was detected in large parts of "Core" and "Prow" as well as the entire "Kite" section. [3]
The persistent movement of the landslide at a constant or increased rate would raise the likelihood for failure. In a worst-case scenario, rapid ground failure could result in a deadly tsunami in large water bodies including Harriman Fiord, Barry Arm, College Fiord, Port Wells, Cochrane Bay, Blackstone Bay, and Passage Canal. A tsunami measuring 30 ft (9.1 m) may strike the town of Whittier, 30 mi (48 km) southwest of the landslide. Scientists said that the tsunami could be fatal to people in the vicinity of the landslide. [2]
According to an interdisciplinary team of researchers in 2020, if the landslide were to fail all at once, a peak run-up of 300 m (980 ft) would occur. Meanwhile run-ups of 30 m (98 ft) would be widely observed around the immediate area. The tsunami would propagate at 24–40 m (79–131 ft) per second across the Prince William Sound, posing a threat to small kayaks and large cruise vessels. Turbidity currents may be triggered by the landslide or tsunami, potentially damaging two submarine cables in the sound. Remaining oil in sediments from the Exxon Valdez oil spill could be remobilized and impact the natural environment. A 10 m (33 ft) tsunami would strike Whittier within 20 minutes of the landslide occurring. The predicted tsunami heights are similar to that of the tsunami from the 1964 Alaska earthquake when it struck the city. [4]
The following year, a report by the U.S. Geological Survey reassessed the tsunami threat posed by the landslide and said that the tsunami 500 m (1,600 ft) offshore Whittier may be slightly over 2 ft (0.61 m) in a worst-case scenario. In this separate scenario, the tsunami would exceed 200 m (660 ft) in the northern part of the fjord. In the southern fjord and at Harriman Fjord, the tsunami waves could be more than 5 m (16 ft). The simulation used data from bathymetric maps by the National Oceanic and Atmospheric Administration and lidar imaging from the Alaska Division of Geological and Geophysical Surveys. [5] The U.S. Geological Survey said that the tsunami hazard is not as severe as initially thought but still pose a threat to coastal settlements. [6]
A tsunami is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions above or below water all have the potential to generate a tsunami. Unlike normal ocean waves, which are generated by wind, or tides, which are in turn generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water from a large event.
Landslides, also known as landslips, 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 occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides.
Prince William Sound is a sound off the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez, at the southern terminus of the Trans-Alaska Pipeline System. Other settlements on the sound, which contains numerous small islands, include Cordova and Whittier plus the Alaska native villages of Chenega and Tatitlek.
A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water.
The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5:36 PM AKST on Good Friday, March 27, 1964. Across south-central Alaska, ground fissures, collapsing structures, and tsunamis resulting from the earthquake caused about 131 deaths.
The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26, 1700, with an estimated moment magnitude of 8.7–9.2. The megathrust earthquake involved the Juan de Fuca Plate from mid-Vancouver Island, south along the Pacific Northwest coast as far as northern California. The plate slipped an average of 20 meters (66 ft) along a fault rupture about 1,000 kilometers long.
The 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1, 1946. The shock measured 8.6, Mt 9.3 or 7.4. It had a maximum Mercalli intensity of VI (Strong). It resulted in 165–173 casualties and over US $26 million in damage. The seafloor along the fault was elevated, triggering a Pacific-wide tsunami with multiple destructive waves at heights ranging from 45–138 ft (14–42 m). The tsunami obliterated the Scotch Cap Lighthouse on Unimak Island, Alaska among others, and killed all five lighthouse keepers. Despite the destruction to the Aleutian Island Unimak, the tsunami had almost an imperceptible effect on the Alaskan mainland.
The Hilina Slump, on the south flank of the Kīlauea Volcano on the southeast coast of the Big Island of Hawaiʻi, is the most notable of several landslides that ring each of the Hawaiian Islands. These landslides are the means by which material deposited at a volcano's vents are transferred downward and seaward, eventually spilling onto the seabed to broaden the island.
The 1957 Andreanof Islands earthquake occurred at 04:22 local time on March 9 with a moment magnitude estimated at 8.6 and a maximum Modified Mercalli intensity of VIII (Severe). It occurred south of the Andreanof Islands group, which is part of the Aleutian Islands arc. The event occurred along the Aleutian Trench, the convergent plate boundary that separates the Pacific Plate and the North American plates near Alaska. A basin-wide tsunami followed, with effects felt in Alaska and Hawaii, and strong waves recorded across the Pacific rim. Total losses were around $5 million.
Icy Bay is a body of water in the borough of Yakutat, Alaska, formed in the last 100 years by the rapid retreat of the Guyot, Yahtse, and Tyndall Glaciers. It is part of the Wrangell-Saint Elias Wilderness.
Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress exceeds the resisting stress of the seafloor slope material, causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings, including planes as low as 1°, and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology.
The 1958 Lituya Bay earthquake occurred on July 9, 1958 at 22:15:58 PST with a moment magnitude of 7.8 to 8.3 and a maximum Mercalli intensity of XI (Extreme). The strike-slip earthquake took place on the Fairweather Fault and triggered a rockslide of 30 million cubic meters and about 90 million tons into the narrow inlet of Lituya Bay, Alaska. The impact was heard 80 kilometers (50 mi) away, and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 524 meters at the entrance of Gilbert Inlet. This is the largest and most significant megatsunami in modern times; it forced a re-evaluation of large-wave events and the recognition of impact events, rockfalls, and landslides as causes of very large waves.
The 1992 Cape Mendocino earthquakes occurred along the Lost Coast of Northern California on April 25 and 26. The three largest events were the M7.2 thrust mainshock that struck near the unincorporated community of Petrolia midday on April 25 and two primary strike-slip aftershocks measuring 6.5 and 6.6 that followed early the next morning. The sequence encompassed both interplate and intraplate activity that was associated with the Mendocino Triple Junction, a complex system of three major faults that converge near Cape Mendocino. The total number of aftershocks that followed the events exceeded 2,000.
A tsunami is a series of water waves caused by the displacement of a large volume within a body of water, often caused by earthquakes, or similar events. This may occur in lakes as well as oceans, presenting threats to both fishermen and shoreside inhabitants. Because they are generated by a near field source region, tsunamis generated in lakes and reservoirs result in a decreased amount of warning time.
The island of La Palma in the Canary Islands is at risk of undergoing a large landslide, which could cause a tsunami in the Atlantic Ocean. Volcanic islands and volcanoes on land frequently undergo large landslides/collapses, which have been documented in Hawaii for example. A recent example is Anak Krakatau, which collapsed to cause the 2018 Sunda Strait tsunami.
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
The 1979 Saint Elias earthquake occurred near noon local time on 28 February. It measured Mw 7.4–7.6. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. The epicenter lies near the Alaskan border between the United States and Canada.
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