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93-588: Establishing an absolute chronology has proved difficult, since different methodologies provide different results. For instance, while carbon dating places the eruption of Thera around 1600 BC, synchronism with Egyptian records would place it roughly a century later. The standard relative chronology divides Minoan history into three eras: Early Minoan (EM) , Middle Minoan (MM) and Late Minoan (LM) . These eras are divided into sub-eras using Roman numerals (e.g. EM I, EM II, EM III) and sub-sub-eras using capital letters (e.g. LM IIIA, LMIIIB, LM IIIC). This system

186-430: A wave shoaling process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. On April 1, 1946, the 8.6 M w   Aleutian Islands earthquake occurred with a maximum Mercalli intensity of VI ( Strong ). It generated a tsunami which inundated Hilo on the island of Hawaii with a 14-metre high (46 ft) surge. Between 165 and 173 were killed. The area where

279-427: A few minutes at a time. The Tauredunum event was a large tsunami on Lake Geneva in 563 CE, caused by sedimentary deposits destabilised by a landslide. In the 1950s, it was discovered that tsunamis larger than had previously been believed possible can be caused by giant submarine landslides . These large volumes of rapidly displaced water transfer energy at a faster rate than the water can absorb. Their existence

372-404: A few thousand years, or even many thousands. Currently, the maximum for fully anchored chronologies is a little over 11,000 years from present. Amino acid dating is a dating technique used to estimate the age of a specimen in paleobiology , archaeology , forensic science , taphonomy , sedimentary geology and other fields. This technique relates changes in amino acid molecules to

465-656: A gradual shift from localized clan-based villages towards the more urbanized and stratified society of later periods. EM I (c. 3100-2650 BC) is marked by the appearance of the first painted ceramics. Continuing a trend that began during the Neolithic, settlements grew in size and complexity, and spread from fertile plains towards highland sites and islands as the Minoans learned to exploit less hospitable terrain. EM II (c. 2650-2200 BC) has been termed an international era. Trade intensified and Minoan ships began sailing beyond

558-432: A huge wave. As the tsunami approaches the coast and the waters become shallow, wave shoaling compresses the wave and its speed decreases below 80 kilometres per hour (50 mph). Its wavelength diminishes to less than 20 kilometres (12 mi) and its amplitude grows enormously—in accord with Green's law . Since the wave still has the same very long period , the tsunami may take minutes to reach full height. Except for

651-541: A large problem of awareness and preparedness, as exemplified by the eruption and collapse of Anak Krakatoa in 2018 , which killed 426 and injured thousands when no warning was available. It is still regarded that lateral landslides and ocean-entering pyroclastic currents are most likely to generate the largest and most hazardous waves from volcanism; however, field investigation of the Tongan event , as well as developments in numerical modelling methods, currently aim to expand

744-538: A massive landslide from Monte Toc entered the reservoir behind the Vajont Dam in Italy. The resulting wave surged over the 262-metre (860 ft)-high dam by 250 metres (820 ft) and destroyed several towns. Around 2,000 people died. Scientists named these waves megatsunamis . Some geologists claim that large landslides from volcanic islands, e.g. Cumbre Vieja on La Palma ( Cumbre Vieja tsunami hazard ) in

837-577: A reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run-up. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are large bodies of water, including lakes. However, tsunami interactions with shorelines and the seafloor topography are extremely complex, which leaves some countries more vulnerable than others. For example,

930-462: A ridge and a trough. In the case of a propagating wave like a tsunami, either may be the first to arrive. If the first part to arrive at the shore is the ridge, a massive breaking wave or sudden flooding will be the first effect noticed on land. However, if the first part to arrive is a trough, a drawback will occur as the shoreline recedes dramatically, exposing normally submerged areas. The drawback can exceed hundreds of metres, and people unaware of

1023-467: A significant tsunami, such as the 1977 Sumba and 1933 Sanriku events. Tsunamis have a small wave height offshore, and a very long wavelength (often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 millimetres (12 in) above the normal sea surface. They grow in height when they reach shallower water, in

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1116-655: A transoceanic tsunami has not occurred within recorded history. Susceptible locations are believed to be the Big Island of Hawaii , Fogo in the Cape Verde Islands , La Reunion in the Indian Ocean , and Cumbre Vieja on the island of La Palma in the Canary Islands ; along with other volcanic ocean islands. This is because large masses of relatively unconsolidated volcanic material occurs on

1209-445: A tsunami can be calculated by obtaining the square root of the depth of the water in metres multiplied by the acceleration due to gravity (approximated to 10 m/s ). For example, if the Pacific Ocean is considered to have a depth of 5000 metres, the velocity of a tsunami would be √ 5000 × 10 = √ 50000 ≈ 224 metres per second (730 ft/s), which equates to a speed of about 806 kilometres per hour (501 mph). This

1302-434: A tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly, resulting in water displacement, owing to the vertical component of movement involved. Movement on normal (extensional) faults can also cause displacement of the seabed, but only the largest of such events (typically related to flexure in the outer trench swell ) cause enough displacement to give rise to

1395-473: A tsunami, which is that of an extraordinarily high tidal bore . Tsunamis and tides both produce waves of water that move inland, but in the case of a tsunami, the inland movement of water may be much greater, giving the impression of an incredibly high and forceful tide. In recent years, the term "tidal wave" has fallen out of favour, especially in the scientific community, because the causes of tsunamis have nothing to do with those of tides , which are produced by

1488-476: Is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated. Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon , a noble gas, is not commonly incorporated into such samples except when produced in situ through radioactive decay. The date measured reveals

1581-467: 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 underwater explosions (including detonations, landslides , glacier calvings , meteorite impacts and other disturbances) 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

1674-620: Is also accustomed to tsunamis, with earthquakes of varying magnitudes regularly occurring off the coast of the island. Tsunamis are an often underestimated hazard in the Mediterranean Sea and parts of Europe. Of historical and current (with regard to risk assumptions) importance are the 1755 Lisbon earthquake and tsunami (which was caused by the Azores–Gibraltar Transform Fault ), the 1783 Calabrian earthquakes , each causing several tens of thousands of deaths and

1767-562: Is also used to refer to the phenomenon because the waves most often are generated by seismic activity such as earthquakes. Prior to the rise of the use of the term tsunami in English, scientists generally encouraged the use of the term seismic sea wave rather than tidal wave . However, like tidal wave , seismic sea wave is not a completely accurate term, as forces other than earthquakes—including underwater landslides , volcanic eruptions, underwater explosions, land or ice slumping into

1860-621: Is based on the sequence of pottery styles excavated at Minoan sites. For instance, the transition from EM III to MM IA is characterized by the appearance of handmade polychrome pottery; the transition from MM IA to MM IB follows the appearance of wheel-made pottery . This framework was originated by Arthur Evans during his excavations at Knossos. It remains the standard in Minoan archaeology, though it has been revised and refined by subsequent researchers and some aspects remain under debate. An alternative framework divides Minoan history based on

1953-496: Is designed to help accurately forecast the passage of tsunamis across oceans as well as how tsunami waves interact with shorelines. The term "tsunami" is a borrowing from the Japanese tsunami 津波 , meaning "harbour wave." For the plural, one can either follow ordinary English practice and add an s , or use an invariable plural as in the Japanese. Some English speakers alter the word's initial / ts / to an / s / by dropping

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2046-404: Is known as the "old wood" problem. It is possible, particularly in dry, desert climates, for organic materials such as dead trees to remain in their natural state for hundreds of years before people use them as firewood or building materials, after which they become part of the archaeological record. Thus, dating that particular tree does not necessarily indicate when the fire burned or the structure

2139-515: Is not favoured by the scientific community because it might give the false impression of a causal relationship between tides and tsunamis. Tsunamis generally consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called " wave train ". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins. The 2004 Indian Ocean tsunami

2232-791: Is now Shakespear Regional Park at the tip of the Whangaparāoa Peninsula in the Auckland Region of New Zealand ; the attempt failed. There has been considerable speculation about the possibility of using nuclear weapons to cause tsunamis near an enemy coastline. Nuclear testing in the Pacific Proving Ground by the United States generated poor results. In Operation Crossroads in July 1946, two 20-kilotonne-of-TNT (84 TJ) bombs were detonated, one in

2325-438: Is of particular significance to the chronology of Minoan history. The Theran eruption plays a role in both the high and low chronological approaches, although there is a difference in the date range each system assigns to the event. In his initial framework, Evans vaguely assigned the eruption to the 17th century BCE. Low chronological assessments revise the eruption to the mid-15th century, while high and blended chronologies push

2418-487: Is often used side-by-side with the ceramic chronology, since the two are commensurate. For instance, the Prepalatial period covers the ceramic phases EM I through MM IA. Establishing an absolute chronology has proved difficult. Archaeologists have attempted to determine calendar dates by synchronizing the periods of Minoan relative chronology with those of better understood neighbors. For example, Minoan artifacts from

2511-426: Is the formula used for calculating the velocity of shallow-water waves. Even the deep ocean is shallow in this sense because a tsunami wave is so long (horizontally from crest to crest) by comparison. The reason for the Japanese name "harbour wave" is that sometimes a village's fishermen would sail out, and encounter no unusual waves while out at sea fishing, and come back to land to find their village devastated by

2604-444: Is the process of determining an age on a specified chronology in archaeology and geology . Some scientists prefer the terms chronometric or calendar dating , as use of the word "absolute" implies an unwarranted certainty of accuracy. Absolute dating provides a numerical age or range, in contrast with relative dating , which places events in order without any measure of the age between events. In archaeology, absolute dating

2697-426: Is used to calculate the equivalent dose (De) that the sediment has acquired since deposition, which can be used in combination with the dose rate (Dr) to calculate the age. Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree rings , also known as growth rings . Dendrochronology can date the time at which tree rings were formed, in many types of wood, to

2790-411: Is usually based on the physical, chemical, and life properties of the materials of artifacts, buildings, or other items that have been modified by humans and by historical associations with materials with known dates (such as coins and historical records ). For example, coins found in excavations may have their production date written on them, or there may be written records describing the coin and when it

2883-430: The 1883 eruption of Krakatoa , and the 2022 Hunga Tonga–Hunga Ha'apai eruption . Over 20% of all fatalities caused by volcanism during the past 250 years are estimated to have been caused by volcanogenic tsunamis. Debate has persisted over the origins and source mechanisms of these types of tsunamis, such as those generated by Krakatoa in 1883, and they remain lesser understood than their seismic relatives. This poses

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2976-688: The 1908 Messina earthquake and tsunami. The tsunami claimed more than 123,000 lives in Sicily and Calabria and is among the deadliest natural disasters in modern Europe. The Storegga Slide in the Norwegian Sea and some examples of tsunamis affecting the British Isles refer to landslide and meteotsunamis , predominantly and less to earthquake-induced waves. As early as 426 BC the Greek historian Thucydides inquired in his book History of

3069-413: The Canary Islands , may be able to generate megatsunamis that can cross oceans, but this is disputed by many others. In general, landslides generate displacements mainly in the shallower parts of the coastline, and there is conjecture about the nature of large landslides that enter the water. This has been shown to subsequently affect water in enclosed bays and lakes, but a landslide large enough to cause

3162-546: The Monopalatial period , as the palace at Knossos was the sole one remaining in use. Late Minoan III (c. 1420-1075 BC) shows profound social and political changes. Among the palaces, only Knossos remained in use, though it too was destroyed by LM IIIB2 and possibly earlier. The language of administration shifted to Mycenaean Greek , written in Linear B , and material culture shows increased mainland influence, reflecting

3255-530: The gravitational pull of the Moon and the Sun , a tsunami is generated by the displacement of water from a large event. Tsunami waves do not resemble normal undersea currents or sea waves because their wavelength is far longer. Rather than appearing as a breaking wave , a tsunami may instead initially resemble a rapidly rising tide . For this reason, it is often referred to as a tidal wave , although this usage

3348-528: The marine style of pottery decoration. Late Minoan I (c. 1700-1470 BC) was a continuation of the prosperous Neopalatial culture. A notable event from this era was the eruption of the Thera volcano , which occurred around 1600 BC towards the end of the LM IA subperiod. One of the largest volcanic explosions in recorded history, it ejected about 60 to 100 cubic kilometres (14 to 24 cu mi) of material and

3441-483: The potter's wheel during MM IB, producing wares such as Kamares ware . MM II (c. 1875-1750 BC) saw the development of the Minoan writing systems, Cretan hieroglyphic and Linear A . It ended with mass destructions generally attributed to earthquakes, though violent destruction has been considered as an alternative explanation. MM III (c. 1750-1700 BC) marks the beginning of the Neopalatial period. Most of

3534-561: The "L" configuration. When an organism dies, control over the configuration of the amino acids ceases, and the ratio of D to L moves from a value near 0 towards an equilibrium value near 1, a process called racemization . Thus, measuring the ratio of D to L in a sample enables one to estimate how long ago the specimen died. Tsunami A tsunami ( /( t ) s uː ˈ n ɑː m i , ( t ) s ʊ ˈ -/ (t)soo- NAH -mee, (t)suu- ; from Japanese : 津波 , lit.   'harbour wave', pronounced [tsɯnami] )

3627-427: The "t," since English does not natively permit /ts/ at the beginning of words, though the original Japanese pronunciation is /ts/ . The term has become commonly accepted in English, although its literal Japanese meaning is not necessarily descriptive of the waves, which do not occur only in harbours. Tsunamis are sometimes referred to as tidal waves . This once-popular term derives from the most common appearance of

3720-516: The Aegean to Egypt and Syria, possibly enabled by the invention of masted ships. Minoan material culture shows increased international influence, for instance in the adoption of Minoan seals based on the older Near Eastern seal . Minoan settlements grew, some doubling in size, and monumental buildings were constructed at sites that would later become palaces. EM III (c. 2200-2100 BC) saw the continuation of these trends. MM I (c. 2100-1875 BC) saw

3813-818: The Great Lakes, the Aegean Sea, the English Channel, and the Balearic Islands, where they are common enough to have a local name, rissaga . In Sicily they are called marubbio and in Nagasaki Bay, they are called abiki . Some examples of destructive meteotsunamis include 31 March 1979 at Nagasaki and 15 June 2006 at Menorca, the latter causing damage in the tens of millions of euros. Meteotsunamis should not be confused with storm surges , which are local increases in sea level associated with

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3906-507: The LM IB ceramic period have been found in 18th Dynasty contexts in Egypt, for which Egyptian chronology provides generally accepted calendar dates. However, dates determined in this manner do not always match the results of carbon dating and other methods based on natural science . Much of the controversy concerns the dating of the eruption of Thera , which is known to have occurred towards

3999-540: The Pacific coasts of the United States and Mexico lie adjacent to each other, but the United States has recorded ten tsunamis in the region since 1788, while Mexico has recorded twenty-five since 1732. Similarly, Japan has had more than a hundred tsunamis in recorded history, while the neighbouring island of Taiwan has registered only two, in 1781 and 1867. All waves have a positive and negative peak; that is,

4092-597: The Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause. The oldest human record of a tsunami dates back to 479 BC , in the Greek colony of Potidaea , thought to be triggered by an earthquake. The tsunami may have saved the colony from an invasion by the Achaemenid Empire . The cause, in my opinion, of this phenomenon must be sought in

4185-450: The air over and one underwater within the shallow waters of the 50-metre (164 ft) deep lagoon at Bikini Atoll . The bombs detonated about 6 km (3.7 mi; 3.2 nmi) from the nearest island, where the waves were no higher than 3 to 4 m (9.8 to 13.1 ft) when they reached the shoreline. Other underwater tests, mainly Operation Hardtack I /Wahoo in deep water and Operation Hardtack I/Umbrella in shallow water, confirmed

4278-570: The construction phases of the Minoan palaces . In this system, the Prepalatial period covers the timespan before the construction of the palaces. The Protopalatial era begins with the construction of the first palaces, and ends with their destruction. The Neopalatial period, often considered the zenith of Minoan civilization, begins with the rebuilding of the palaces, and ends with yet another wave of destructions. The Postpalatial period covers

4371-413: The danger sometimes remain near the shore to satisfy their curiosity or to collect fish from the exposed seabed. A typical wave period for a damaging tsunami is about twelve minutes. Thus, the sea recedes in the drawback phase, with areas well below sea level exposed after three minutes. For the next six minutes, the wave trough builds into a ridge which may flood the coast, and destruction ensues. During

4464-583: The date back to a point in between Evans' and low chronologies, a more commonly accepted specific date of approximately 1628, though the date is by no means generally agreed. The precise date is of more concern to archaeologists of the Asian mainland and Ancient Egypt, where volcanic ash from Thera is widely evident, and there are established competing chronologies, than to those of Crete. High chronological techniques such as radiocarbon dating can be used in conjunction with evidence from artifacts indirectly related to

4557-465: The date of death of the organic matter in an artifact or ecofact . The relatively short half-life of carbon-14, 5,730 years, makes dating reliable only up to about 60,000 years. The technique often cannot pinpoint the date of an archeological site better than historic records but is highly effective for precise dates when calibrated with other dating techniques such as tree-ring dating . An additional problem with carbon-14 dates from archeological sites

4650-455: The deep ocean has a much larger wavelength of up to 200 kilometres (120 mi). Such a wave travels at well over 800 kilometres per hour (500 mph), but owing to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about 1 metre (3.3 ft). This makes tsunamis difficult to detect over deep water, where ships are unable to feel their passage. The velocity of

4743-494: The earthquake occurred is where the Pacific Ocean floor is subducting (or being pushed downwards) under Alaska. Examples of tsunamis originating at locations away from convergent boundaries include Storegga about 8,000 years ago, Grand Banks in 1929, and Papua New Guinea in 1998 (Tappin, 2001). The Grand Banks and Papua New Guinea tsunamis came from earthquakes which destabilised sediments, causing them to flow into

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4836-408: The earthquake. At the point where its shock has been the most violent the sea is driven back, and suddenly recoiling with redoubled force, causes the inundation. Without an earthquake I do not see how such an accident could happen. The Roman historian Ammianus Marcellinus ( Res Gestae 26.10.15–19) described the typical sequence of a tsunami, including an incipient earthquake, the sudden retreat of

4929-415: The emergence of Protopalatial society. During MM IA (c. 2100-1925 BC), populations increased dramatically at sites such as Knossos, Phaistos, and Malia, accompanied by major construction projects. During MM IB (c. 1925-1875 BC), the first palaces were built at these sites, in areas which had been used for communal ceremonies since the Neolithic. Middle Minoan artisans developed new colorful paints and adopted

5022-460: The end of the LM IA period. While carbon dating places this event (and thus LM IA) around 1600 BC, synchronism with Egyptian records would place it roughly a century later. The timing of natural disasters is of importance to high and low chronologies, which can use the resulting geological evidence to date co-located artifacts. The eruption of the Thera volcano on what is now the island of Santorini

5115-467: The era in which Minoan culture continued in the absence of the palaces. Some variants of this system include a Final palace period or a Monopalatial period between the Neo- and Postpalatial periods, corresponding to era when the palace at Knossos was reoccupied. The architectural periodization was proposed by Nikolaos Platon in 1961, though later scholars have proposed variants and refinements. This system

5208-494: The eruption, such as eruption-caused tsunami debris to pinpoint the exact timing of the event, and therefore which Minoan period it belongs in. However, the broadness of radiocarbon dating has also resulted in dates for the eruption of Thera that do not precisely match evidence from the archeological record. Early Minoan society developed largely continuously from local Neolithic predecessors, with some cultural influence and perhaps migration from eastern populations. This period saw

5301-400: The exact calendar year. Dendrochronology has three main areas of application: paleoecology , where it is used to determine certain aspects of past ecologies (most prominently climate); archaeology , where it is used to date old buildings, etc.; and radiocarbon dating , where it is used to calibrate radiocarbon ages (see below). In some areas of the world, it is possible to date wood back

5394-406: The flanks and in some cases detachment planes are believed to be developing. However, there is growing controversy about how dangerous these slopes actually are. Other than by landslides or sector collapse , volcanoes may be able to generate waves by pyroclastic flow submergence, caldera collapse, or underwater explosions. Tsunamis have been triggered by a number of volcanic eruptions, including

5487-441: The food chain as animals eat plants and as predators eat other animals. With death, the uptake of carbon-14 stops. It takes 5,730 years for half the carbon-14 to decay to nitrogen; this is the half-life of carbon-14. After another 5,730 years, only one-quarter of the original carbon-14 will remain. After yet another 5,730 years, only one-eighth will be left. By measuring the carbon-14 in organic material , scientists can determine

5580-494: The gravitational pull of the moon and sun rather than the displacement of water. Although the meanings of "tidal" include "resembling" or "having the form or character of" tides, use of the term tidal wave is discouraged by geologists and oceanographers. A 1969 episode of the TV crime show Hawaii Five-O entitled "Forty Feet High and It Kills!" used the terms "tsunami" and "tidal wave" interchangeably. The term seismic sea wave

5673-409: The harbour at Halifax , Nova Scotia , Canada . There have been studies of the potential for the use of explosives to induce tsunamis as a tectonic weapon . As early as World War II (1939–1945), consideration of the use of conventional explosives was explored, and New Zealand's military forces initiated Project Seal , which attempted to create small tsunamis with explosives in the area of what

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5766-557: The intensity of tsunamis were the Sieberg - Ambraseys scale (1962), used in the Mediterranean Sea and the Imamura-Iida intensity scale (1963), used in the Pacific Ocean. The latter scale was modified by Soloviev (1972), who calculated the tsunami intensity " I " according to the formula: where H a v {\displaystyle {\mathit {H}}_{av}} is the "tsunami height" in metres, averaged along

5859-562: The intensively studied tsunamis in 2004 and 2011, a new 12-point scale was proposed, the Integrated Tsunami Intensity Scale (ITIS-2012), intended to match as closely as possible to the modified ESI2007 and EMS earthquake intensity scales. The first scale that genuinely calculated a magnitude for a tsunami, rather than an intensity at a particular location was the ML scale proposed by Murty & Loomis based on

5952-432: The island, marking the end of Neopalatial society. These destructions are thought to have been deliberate, since they spared certain sites in a manner inconsistent with natural disasters. For instance, the town at Knossos burned while the palace itself did not. The causes of these destructions have been a perennial topic of debate. While some researchers attributed them to Mycenaean conquerors, others have argued that they were

6045-428: The item. Heating an item to 500 degrees Celsius or higher releases the trapped electrons , producing light. This light can be measured to determine the last time the item was heated. Radiation levels do not remain constant over time. Fluctuating levels can skew results – for example, if an item went through several high radiation eras, thermoluminescence will return an older date for the item. Many factors can spoil

6138-446: The last time that the object was heated past the closure temperature at which the trapped argon can escape the lattice. K–Ar dating was used to calibrate the geomagnetic polarity time scale . Thermoluminescence testing also dates items to the last time they were heated. This technique is based on the principle that all objects absorb radiation from the environment. This process frees electrons within minerals that remain caught within

6231-483: The low barometric pressure of passing tropical cyclones, nor should they be confused with setup, the temporary local raising of sea level caused by strong on-shore winds. Storm surges and setup are also dangerous causes of coastal flooding in severe weather but their dynamics are completely unrelated to tsunami waves. They are unable to propagate beyond their sources, as waves do. The accidental Halifax Explosion in 1917 triggered an 18-metre (59 ft) high tsunami in

6324-636: The nearest coastline, with the tsunami height defined as the rise of the water level above the normal tidal level at the time of occurrence of the tsunami. This scale, known as the Soloviev-Imamura tsunami intensity scale , is used in the global tsunami catalogues compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami. This formula yields: In 2013, following

6417-405: The next six minutes, the wave changes from a ridge to a trough, and the flood waters recede in a second drawback. Victims and debris may be swept into the ocean. The process repeats with succeeding waves. As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events. The first scales used routinely to measure

6510-856: The ocean and generate a tsunami. They dissipated before travelling transoceanic distances. The cause of the Storegga sediment failure is unknown. Possibilities include an overloading of the sediments, an earthquake or a release of gas hydrates (methane etc.). The 1960 Valdivia earthquake ( M w 9.5), 1964 Alaska earthquake ( M w 9.2), 2004 Indian Ocean earthquake ( M w 9.2), and 2011 Tōhoku earthquake ( M w 9.0) are recent examples of powerful megathrust earthquakes that generated tsunamis (known as teletsunamis ) that can cross entire oceans. Smaller ( M w 4.2) earthquakes in Japan can trigger tsunamis (called local and regional tsunamis) that can devastate stretches of coastline, but can do so in only

6603-437: The ocean, meteorite impacts, and the weather when the atmospheric pressure changes very rapidly—can generate such waves by displacing water. The use of the term tsunami for waves created by landslides entering bodies of water has become internationally widespread in both scientific and popular literature, although such waves are distinct in origin from large waves generated by earthquakes. This distinction sometimes leads to

6696-472: The oldest rocks on Earth. Radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes . Particular isotopes are suitable for different applications due to the types of atoms present in the mineral or other material and its approximate age. For example, techniques based on isotopes with half-lives in the thousands of years, such as carbon-14, cannot be used to date materials that have ages on

6789-556: The order of billions of years, as the detectable amounts of the radioactive atoms and their decayed daughter isotopes will be too small to measure within the uncertainty of the instruments. One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon ) dating, which is used to date organic remains. This is a radiometric technique since it is based on radioactive decay. Cosmic radiation entering Earth's atmosphere produces carbon-14, and plants take in carbon-14 as they fix carbon dioxide. Carbon-14 moves up

6882-503: The palaces were rebuilt with architectural innovations, with the notable exception of Phaistos. Cretan hieroglyphs were abandoned in favor of Linear A, and Minoan cultural influence becomes significant in mainland Greece. The Late Minoan period was an eventful time that saw profound change in Minoan society. Many of the most recognizable Minoan artifacts date from this time, for instance the Snake goddess figurines , La Parisienne Fresco , and

6975-482: The possibility of a meteorite causing a tsunami is debated. Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. More specifically,

7068-433: The potential energy. Difficulties in calculating the potential energy of the tsunami mean that this scale is rarely used. Abe introduced the tsunami magnitude scale M t {\displaystyle {\mathit {M}}_{t}} , calculated from, where h is the maximum tsunami-wave amplitude (in m) measured by a tide gauge at a distance R from the epicentre, a , b and D are constants used to make

7161-409: The result of internal upheavals. Similarly, while some researchers have attempted to link them to lingering environmental disruption from the Thera eruption, others have argued that the two events are too distant in time for any causal relation. Late Minoan II (c. 1470-1420 BC) is sparsely represented in the archaeological record, but appears to have been a period of decline. It marks the beginning of

7254-605: The results. Analysis of the effects of shallow and deep underwater explosions indicate that the energy of the explosions does not easily generate the kind of deep, all-ocean waveforms typical of tsunamis because most of the energy creates steam , causes vertical fountains above the water, and creates compressional waveforms. Tsunamis are hallmarked by permanent large vertical displacements of very large volumes of water which do not occur in explosions. Tsunamis are caused by earthquakes, landslides, volcanic explosions, glacier calvings, and bolides . They cause damage by two mechanisms:

7347-475: The rise of a Greek-speaking elite. In Late Minoan IIIC (c. 1200-1075 BC), coinciding with the wider Late Bronze Age collapse , coastal settlements were abandoned in favor of defensible locations on higher ground. These small villages, some of which grew out of earlier mountain shrines, continued aspects of recognizably Minoan culture until the Early Iron Age . Absolute dating Absolute dating

7440-429: The sample before testing as well, exposing the sample to heat or direct light may cause some of the electrons to dissipate, causing the item to date younger. Because of these and other factors, Thermoluminescence is at the most about 15% accurate. It cannot be used to accurately date a site on its own. However, it can be used to confirm the antiquity of an item. Optically stimulated luminescence (OSL) dating constrains

7533-426: The sea and a following gigantic wave, after the 365 AD tsunami devastated Alexandria . The principal generation mechanism of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually caused by earthquakes, but can also be attributed to landslides, volcanic eruptions, glacier calvings or more rarely by meteorites and nuclear tests. However,

7626-400: The smashing force of a wall of water travelling at high speed, and the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it, even with waves that do not appear to be large. While everyday wind waves have a wavelength (from crest to crest) of about 100 metres (330 ft) and a height of roughly 2 metres (6.6 ft), a tsunami in

7719-490: The time at which sediment was last exposed to light. During sediment transport, exposure to sunlight 'zeros' the luminescence signal. Upon burial, the sediment accumulates a luminescence signal as natural ambient radiation gradually ionises the mineral grains. Careful sampling under dark conditions allows the sediment to be exposed to artificial light in the laboratory which releases the OSL signal. The amount of luminescence released

7812-401: The time elapsed since they were formed. All biological tissues contain amino acids . All amino acids except glycine (the simplest one) are optically active , having an asymmetric carbon atom. This means that the amino acid can have two different configurations, "D" or "L" which are mirror images of each other. With a few important exceptions, living organisms keep all their amino acids in

7905-457: The transoceanic reach of significant seismic tsunamis, and 2) that the force that displaces the water is sustained over some length of time such that meteotsunamis cannot be modelled as having been caused instantaneously. In spite of their lower energies, on shorelines where they can be amplified by resonance, they are sometimes powerful enough to cause localised damage and potential for loss of life. They have been documented in many places, including

7998-447: The understanding of the other source mechanisms. Some meteorological conditions, especially rapid changes in barometric pressure, as seen with the passing of a front, can displace bodies of water enough to cause trains of waves with wavelengths. These are comparable to seismic tsunamis, but usually with lower energies. Essentially, they are dynamically equivalent to seismic tsunamis, the only differences being 1) that meteotsunamis lack

8091-457: The use of other terms for landslide-generated waves, including landslide-triggered tsunami , displacement wave , non-seismic wave , impact wave , and, simply, giant wave . While Japan may have the longest recorded history of tsunamis, the sheer destruction caused by the 2004 Indian Ocean earthquake and tsunami event mark it as the most devastating of its kind in modern times, killing around 230,000 people. The Sumatran region

8184-399: The very largest tsunamis, the approaching wave does not break , but rather appears like a fast-moving tidal bore . Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami's wave peak reaches the shore, the resulting temporary rise in sea level is termed run up . Run up is measured in metres above

8277-576: Was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries bordering the Indian Ocean . The Ancient Greek historian Thucydides suggested in his 5th century BC History of the Peloponnesian War that tsunamis were related to submarine earthquakes , but the understanding of tsunamis remained slim until the 20th century, and much remains unknown. Major areas of current research include determining why some large earthquakes do not generate tsunamis while other smaller ones do. This ongoing research

8370-442: Was built. For this reason, many archaeologists prefer to use samples from short-lived plants for radiocarbon dating. The development of accelerator mass spectrometry (AMS) dating, which allows a date to be obtained from a very small sample, has been very useful in this regard. Other radiometric dating techniques are available for earlier periods. One of the most widely used is potassium–argon dating (K–Ar dating). Potassium-40

8463-521: Was confirmed in 1958, when a giant landslide in Lituya Bay , Alaska, caused the highest wave ever recorded, which had a height of 524 metres (1,719 ft). The wave did not travel far as it struck land almost immediately. The wave struck three boats—each with two people aboard—anchored in the bay. One boat rode out the wave, but the wave sank the other two, killing both people aboard one of them. Another landslide-tsunami event occurred in 1963 when

8556-564: Was measured at 7 on the Volcanic Explosivity Index . While the eruption destroyed Cycladic settlements such as Akrotiri and led to the abandonment of some sites in northeast Crete, other Minoan sites such as Knossos continued to prosper. The post-eruption LM IB period (c.1625-1470) saw ambitious new building projects, booming international trade, and artistic developments such as the marine style . Late Minoan IB (c. 1625-1470 BC) ended with severe destructions throughout

8649-603: Was used, allowing the site to be associated with a particular calendar year. Absolute dating techniques include radiocarbon dating of wood or bones, potassium-argon dating , and trapped-charge dating methods such as thermoluminescence dating of glazed ceramics. In historical geology , the primary methods of absolute dating involve using the radioactive decay of elements trapped in rocks or minerals, including isotope systems from younger organic remains (radiocarbon dating with C ) to systems such as uranium–lead dating that allow determination of absolute ages for some of

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