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Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, shallow or deep-seated slope failures, mudflows, 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.
Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers wide and 3 to 4 km below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about 50,000 km (31,000 mi) of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of 10,920 m (35,830 ft) below sea level.
A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water.
A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or a rock layer moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Causes of slumping include earthquake shocks, thorough wetting, freezing and thawing, undercutting, and loading of a slope.
The 1929 Grand Banks earthquake occurred on November 18, 1929. The shock had a moment magnitude of 7.2 and a maximum Rossi–Forel intensity of VI and was centered in the Atlantic Ocean off the south coast of Newfoundland in the Laurentian Slope Seismic Zone.
A submarine canyon is a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km (3 mi), from canyon floor to canyon rim, as with the Great Bahama Canyon. Just as above-sea-level canyons serve as channels for the flow of water across land, submarine canyons serve as channels for the flow of turbidity currents across the seafloor. Turbidity currents are flows of dense, sediment laden waters that are supplied by rivers, or generated on the seabed by storms, submarine landslides, earthquakes, and other soil disturbances. Turbidity currents travel down slope at great speed, eroding the continental slope and finally depositing sediment onto the abyssal plain, where the particles settle out.
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.
A chevron is a wedge-shaped sediment deposit observed on coastlines and continental interiors around the world. The term chevron was originally used independently by Maxwell and Haynes and Hearty and others for large, V-shaped, sub-linear to parabolic landforms in southwestern Egypt and on islands in the eastern, windward Bahamas.
The 1998 Papua New Guinea earthquake occurred on July 17 with a moment magnitude of 7.0 and a maximum Mercalli intensity of VIII (Severe). The event occurred on a reverse fault near the north coast region of Papua New Guinea, 25 kilometers (16 mi) from the coast near Aitape, and caused a large undersea landslide which caused a tsunami that hit the coast, killing between at least 2,183 and 2,700 people and injuring thousands.
Tsunamis affecting the British Isles are extremely uncommon, and there have only been two confirmed cases in recorded history. Meteotsunamis are somewhat more common, especially on the southern coasts of England around the English and Bristol Channels.
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 1692 Jamaica earthquake struck Port Royal, Jamaica, on 7 June. A stopped pocket watch found in the harbor during a 1959 excavation indicated that it occurred around 11:43 AM local time.
Marsili is a large undersea volcano in the Tyrrhenian Sea, about 175 kilometers (109 mi) south of Naples. The seamount is about 3,000 m tall; its peak and crater are about 450 m below the sea surface. Though it has not erupted in recorded history, volcanologists believe that Marsili is a relatively fragile-walled structure, made of low-density and unstable rocks, fed by the underlying shallow magma chamber. Volcanologists with the Italian National Institute of Geophysics and Volcanology (INGV) announced on March 29, 2010, that Marsili could erupt at any time, and might experience a catastrophic collapse that would suddenly release vast amounts of magma in an undersea eruption and landslide that could trigger destructive tsunamis on the Italian coast and nearby Mediterranean coastlines.
The 1993 southwest-off Hokkaido earthquake or Okushiri earthquake occurred at 13:17:12 UTC on 12 July 1993 in the Sea of Japan near the island of Hokkaido. It had a magnitude of 7.7 on the moment magnitude scale and a maximum felt intensity of VIII (Severe) on the Mercalli intensity scale. It triggered a major tsunami that caused deaths on Hokkaidō and in southeastern Russia, with a total of 230 fatalities recorded. The island of Okushiri was hardest hit, with 165 casualties from the earthquake, the tsunami and a large landslide.
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.
The devastating eruption of Oshima–Ōshima began on the 18th of August, 1741 and ended on May 1 the next year. Eleven days into the eruption, the Kampo tsunami with estimated maximum heights of over 90 meters swept across neighboring islands in Japan and the Korean Peninsula.
The Kaikōura Canyon is a geologically active submarine canyon located southwest of the Kaikōura Peninsula off the northeastern coast of the South Island of New Zealand. It is 60 kilometres (37 mi) long, and is generally U-shaped. The canyon descends into deep water and merges into an ocean channel system that can be traced for hundreds of kilometres across the deep ocean floor. At the head of the Kaikōura Canyon, the depth of water is around 30 metres (98 ft), but it drops rapidly to 600 metres (2,000 ft) and continues down to around 2,000 metres (6,600 ft) deep where it meets the Hikurangi Channel. Sperm whales can be seen close to the coast south of Goose Bay, because the deep water of the Kaikōura Canyon is only one kilometre (0.62 mi) off the shoreline in this area.
The 1867 Keelung earthquake occurred off the northern coast of Taiwan on the morning of December 18 with a magnitude of 7.0. It produced strong shaking that seriously damaged the cities of Keelung and Taipei. A tsunami, thought to be the only confirmed destructive of its kind in Taiwan, drowned hundreds and had a run-up exceeding 15 m (49 ft). The total death toll was estimated to be 580 while more than 100 were injured. It was followed by aftershocks that were felt on average ten times a day.
A volcanic landslide or volcanogenic landslide is a type of mass wasting that takes place at volcanoes.
References
- 1 2 Allaby, M. (2004). A Chronology of Weather. Infobase Publishing.
- 1 2 3 4 Sahal, Alexandre; Lemahieu, Anne (2010). "The 1979 nice airport tsunami: mapping of the flood in Antibes". Natural Hazards. 56 (3): 833–840. doi:10.1007/s11069-010-9594-6. ISSN 0921-030X. S2CID 128751536.
- ↑ Lee, Homa J.; Locat, Jacques; Desgagns, Priscilla; Parsons, Jeffrey D.; McAdoo, Brian G.; Orange, Daniel L.; Puig, Pere; Wong, Florence L.; Dartnell, Peter; Boulanger, Eric (2007). "Submarine Mass Movements on Continental Margins". Continental Margin Sedimentation. Oxford, UK: Blackwell Publishing Ltd. pp. 213–274. doi:10.1002/9781444304398.ch5. ISBN 978-1-4443-0439-8.
- 1 2 3 Seed, H. B. (1988). The landslide at the Port of Nice on October 16, 1979. Earthquake Engineering Research Center, University of California.
- ↑ Nisbet, Euan G.; Piper, David J. W. (1998). "Giant submarine landslides". Nature. 392 (6674): 329–330. Bibcode:1998Natur.392..329N. doi: 10.1038/32765 . ISSN 0028-0836.
- ↑ Rana, S. V. S. (2007). Essentials of ecology and environmental science. PHI Learning Pvt. Ltd.
- ↑ Dudley, W. C., & Lee, M. (1998). Tsunami!. University of Hawaii Press.