The three Storegga Slides are considered to be amongst the largest known landslides. They occurred under water, at the edge of Norway's continental shelf in the Norwegian Sea, approximately 6225–6170 BC. The collapse involved an estimated 290 km (180 mi) length of coastal shelf, with a total volume of 3,500 km3 (840 cu mi) of debris, which caused a very large tsunami in the North Atlantic Ocean.
The three Storegga Slides are considered to be amongst the largest known landslides. They occurred under water, at the edge of Norway's continental shelf (Storegga is Norwegian for "the Great Edge"), in the Norwegian Sea, 100 km (62 mi) north-west of the Møre coast, causing a very large tsunami in the North Atlantic Ocean. This collapse involved an estimated 290 km (180 mi) length of coastal shelf, with a total volume of 3,500 km3 (840 cu mi) of debris. This would be the equivalent volume to an area the size of Iceland covered to a depth of 34 m (112 ft).
Based on carbon dating of plant material recovered from sediment deposited by the tsunami, the latest incident occurred around approximately 6225–6170 BC. In Scotland, traces of the subsequent tsunami have been recorded, with deposited sediment being discovered in Montrose Basin, the Firth of Forth, up to 80 km (50 mi) inland and 4 m (13 ft) above current normal tide levels.
A possible triggering mechanism is thought to have been an earthquake physically triggering a catastrophic expansion of methane hydrates. A cubic metre of solid hydrate expands to 164 cubic metres of methane.
Another theory is that streams from melting glaciers had carried trillions of tons of sediment to the edge of the continental shelf, and that a trigger such as an earthquake caused a massive area of seafloor to collapse into the deep Norwegian sea.
At, or shortly before, the time of the last Storegga Slide, a land bridge known to archaeologists and geologists as "Doggerland" existed, linking Britain, Denmark and the Netherlands across what is now the southern North Sea. This area is believed to have included a coastline of lagoons, marshes, mudflats, and beaches, and to have been a rich hunting, fowling and fishing ground populated by Mesolithic human cultures.
Although Doggerland was permanently submerged through a gradual rise in sea level, it has been suggested that coastal areas of both Britain and mainland Europe, extending over areas which are now submerged, would have been temporarily inundated by a tsunami triggered by the Storegga Slide. This event would have had a catastrophic impact on the contemporary Mesolithic population.
As part of the activities to prepare the Ormen Lange natural gas field, the incident has been thoroughly investigated. One conclusion is that the slide was caused by material built up during the previous glacial period and that a recurrence would be possible only after a new ice age. Facts and arguments supporting this conclusion were made public in 2004, and thus it was concluded that the development of the Ormen Lange gas field would not significantly increase the risk of triggering a new slide.
In climatology, the 8.2-kiloyear event was a sudden decrease in global temperatures that occurred approximately 8,200 years before the present, or c. 6,200 BC, and which lasted for the next two to four centuries. It defines the start of the Northgrippian age in the Holocene epoch. Milder than the Younger Dryas cold spell before it but more severe than the Little Ice Age after it, the 8.2-kiloyear cooling was a significant exception to general trends of the Holocene climatic optimum. During the event, atmospheric methane concentration decreased by 80 ppb, an emission reduction of 15%, by cooling and drying at a hemispheric scale.Atlantis
Atlantis (Ancient Greek: Ἀτλαντὶς νῆσος, "island of Atlas") is a fictional island mentioned within an allegory on the hubris of nations in Plato's works Timaeus and Critias, where it represents the antagonist naval power that besieges "Ancient Athens", the pseudo-historic embodiment of Plato's ideal state in The Republic. In the story, Athens repels the Atlantean attack unlike any other nation of the known world, supposedly giving testament to the superiority of Plato's concept of a state. The story concludes with Atlantis falling out of favor with the deities and submerging into the Atlantic Ocean.
Despite its minor importance in Plato's work, the Atlantis story has had a considerable impact on literature. The allegorical aspect of Atlantis was taken up in utopian works of several Renaissance writers, such as Francis Bacon's New Atlantis and Thomas More's Utopia. On the other hand, nineteenth-century amateur scholars misinterpreted Plato's narrative as historical tradition, most notably in Ignatius L. Donnelly's Atlantis: The Antediluvian World. Plato's vague indications of the time of the events—more than 9,000 years before his time—and the alleged location of Atlantis—"beyond the Pillars of Hercules"—has led to much pseudoscientific speculation. As a consequence, Atlantis has become a byword for any and all supposed advanced prehistoric lost civilizations and continues to inspire contemporary fiction, from comic books to films.
While present-day philologists and classicists agree on the story's fictional character, there is still debate on what served as its inspiration. As for instance with the story of Gyges, Plato is known to have freely borrowed some of his allegories and metaphors from older traditions. This led a number of scholars to investigate possible inspiration of Atlantis from Egyptian records of the Thera eruption, the Sea Peoples invasion, or the Trojan War. Others have rejected this chain of tradition as implausible and insist that Plato created an entirely fictional nation as his example, drawing loose inspiration from contemporary events such as the failed Athenian invasion of Sicily in 415–413 BC or the destruction of Helike in 373 BC.Clathrate hydrate
Clathrate hydrates, or gas clathrates, gas hydrates, clathrates, hydrates, etc., are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded, frozen water molecules. In other words, clathrate hydrates are clathrate compounds in which the host molecule is water and the guest molecule is typically a gas or liquid. Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water. Most low molecular weight gases, including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe, as well as some higher hydrocarbons and freons, will form hydrates at suitable temperatures and pressures. Clathrate hydrates are not officially chemical compounds, as the sequestered molecules are never bonded to the lattice. The formation and decomposition of clathrate hydrates are first order phase transitions, not chemical reactions. Their detailed formation and decomposition mechanisms on a molecular level are still not well understood.
Clathrate hydrates were first documented in 1810 by Sir Humphry Davy who found that water was a primary component of what was earlier thought to be solidified chlorine.Clathrates have been found to occur naturally in large quantities. Around 6.4 trillion (6.4×1012) tonnes of methane is trapped in deposits of methane clathrate on the deep ocean floor. Such deposits can be found on the Norwegian continental shelf in the northern headwall flank of the Storegga Slide. Clathrates can also exist as permafrost, as at the Mallik gas hydrate site in the Mackenzie Delta of northwestern Canadian Arctic. These natural gas hydrates are seen as a potentially vast energy resource, but an economical extraction method has so far proven elusive. Hydrocarbon clathrates cause problems for the petroleum industry, because they can form inside gas pipelines, often resulting in obstructions. Deep sea deposition of carbon dioxide clathrate has been proposed as a method to remove this greenhouse gas from the atmosphere and control climate change.
Clathrates are suspected to occur in large quantities on some outer planets, moons and trans-Neptunian objects, binding gas at fairly high temperatures.Doggerland
Doggerland was an area of land, now submerged beneath the southern North Sea, that connected Britain to continental Europe. It was flooded by rising sea levels around 6500–6200 BC. Geological surveys have suggested that it stretched from Britain's east coast to the Netherlands and the western coasts of Germany and the peninsula of Jutland. It was probably a rich habitat with human habitation in the Mesolithic period, although rising sea levels gradually reduced it to low-lying islands before its final submergence, possibly following a tsunami caused by the Storegga Slide.The archaeological potential of the area was first identified in the early 20th century, and interest intensified in 1931 when a fishing trawler operating east of the Wash dragged up a barbed antler point that was subsequently dated to a time when the area was tundra. Vessels have dragged up remains of mammoths, lions and other animals, and a few prehistoric tools and weapons.Doggerland was named in the 1990s, after the Dogger Bank, which in turn was named after the 17th century Dutch fishing boats called doggers.Geohazard
A geohazard is a geological state that may lead to widespread damage or risk. Geohazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions (e.g., submarine or surface landslide) and affect local and regional socio-economy to a large extent (e.g., tsunamis).Heart Mountain (Wyoming)
Heart Mountain is an 8,123-foot (2,476 m) klippe just north of Cody in the U.S. state of Wyoming, rising from the floor of the Bighorn Basin. The mountain is composed of limestone and dolomite of Ordovician through Mississippian age (about 500 to 350 million years old), but it rests on the Willwood Formation, rocks that are about 55 million years old—rock on the summit of Heart Mountain is thus almost 300 million years older than the rocks at the base. For over one hundred years, geologists have tried to understand how these older rocks came to rest on much younger strata.
The carbonate rocks that form Heart Mountain were deposited on a basement of ancient (more than 2.5 billion years old) granite when the area was covered by a large shallow tropical sea. Up until 50 million years ago, these rocks lay about 25 miles (40 kilometers) to the northwest, where the eastern Absaroka Range now stands.
Between 75 and 50 million years ago, a period of mountain-building called the Laramide Orogeny caused uplift of the Beartooth Range and subsidence of the Bighorn and Absaroka Basins. Just south of the Beartooth Range, this orogeny uplifted an elongate, somewhat lower plateau which sloped gently to the southeast toward the Bighorn Basin and to the south toward the Absaroka Basin. Immediately following this period of mountain-building, volcanic eruptions began to form the now extinct volcanoes of the Absaroka Range that lie to the south of the Beartooths and extend into Yellowstone National Park. Between 50 and 48 million years ago a sheet of rock about 500 square miles (1,300 square kilometers) in area detached from the plateau south of the Beartooths and slid tens of kilometers to the southeast and south into the Bighorn and Absaroka Basins. This sheet, consisting of Ordovician through Mississippian carbonate rocks and overlying Absaroka volcanic rocks, was probably originally about 4–5 kilometers thick. Although the slope was less than 2 degrees, the front of the landslide traveled at least 25 miles (40 km) and the slide mass ended up covering over 1,300 square miles (>3,400 km2). This is by far the largest rockslide known on land on the surface of the earth and is comparable in scale to some of the largest known submarine landslides.Many models have been proposed to explain what caused this huge slab of rocks to start sliding and what allowed it to slide so far on such a low slope, fragmenting, thinning and extending as it went. Most geologists who have worked in the area agree that Absaroka volcanism played a role in the sliding and many suggest that a major volcanic or steam explosion initiated movement. Another model involves injection of numerous igneous dikes with the resulting heating of water within pores in rocks causing an increase in pressure which initiated sliding. Some geologists have suggested that hot pressurized water (hydrothermal fluids), derived from a volcano which sat north of Cooke City, Montana, effectively lubricated the sliding surface. Another possibility is that once the slide was moving, friction heated the limestone along the sliding surface, creating pseudotachylite, which then further broke down to calcium oxide and carbon dioxide gas (or supercritical fluid). The gas supported the slide in the way that air pressure supports a hovercraft, allowing the slide to move easily down the very low slope. When the rockslide stopped, the carbon dioxide cooled and recombined with calcium oxide to form the cement-like carbonate rock now found in the fault zone. The consensus favors catastrophic sliding and calculations suggest that the front of the sliding mass may have advanced at a speed of over 100 miles/hour (160 km/h), meaning that the mountain traveled to its present location in approximately 30 minutes.In the 48 million years since the slide occurred, erosion has removed most of the portion of the slide sheet which moved out into the Bighorn Basin, leaving just one big block of carbonate rocks—Heart Mountain. Farther south, a large block of carbonate rock forms Sheep Mountain, which lies just south of the road that goes from Cody into Yellowstone Park. Some of the best views of the sliding surface, called the Heart Mountain fault, can be found along the Chief Joseph Highway (Wyoming Highway 296). The fault is particularly well exposed in Cathedral Cliffs, where it appears as a remarkably straight and nearly horizontal line just above a 2–3-meter-high cliff.
The nearby Heart Mountain War Relocation Center, where a number of Japanese Americans were interned during World War II, was named after the peak.Landslide
The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, 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. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable.List of tsunamis
This article lists notable tsunamis, which are sorted by the date and location that the tsunami occurred.
Because of seismic and volcanic activity associated with tectonic plate boundaries along the Pacific Ring of Fire, tsunamis occur most frequently in the Pacific Ocean, but are a worldwide natural phenomenon. They are possible wherever large bodies of water are found, including inland lakes, where they can be caused by landslides and glacier calving. Very small tsunamis, non-destructive and undetectable without specialized equipment, occur frequently as a result of minor earthquakes and other events.
Around 1600 BCE, a tsunami caused by the eruption of Thira devastated the Minoan civilization on Crete and related cultures in the Cyclades, as well as in areas on the Greek mainland facing the eruption, such as the Argolid.
The oldest recorded tsunami occurred in 479 BCE. It destroyed a Persian army that was attacking the town of Potidaea in Greece.As early as 426 BCE, the Greek historian Thucydides inquired in his book History of the Peloponnesian War (3.89.1–6) about the causes of tsunamis. He argued that such events could only be explained as a consequence of ocean earthquakes, and could see no other possible causes.List of tsunamis in Europe
The following is a list of notable tsunamis in Europe.Location hypotheses of Atlantis
Location hypotheses of Atlantis are various proposed real-world settings for the fictional island of Atlantis, described as a lost civilization mentioned in Plato's dialogues Timaeus and Critias, written about 360 B.C. In these dialogues, a character named Critias claims that an island called Atlantis was swallowed by the sea about 9,200 years previously. According to the dialogues, this story was passed down to him through his grandfather, also named Critias, who in turn got it from his father, Dropides, who had got it from Solon, the famous Athenian lawmaker, who had got the story from an Egyptian sanctuary. Plato's dialogues locate the island in the Atlantic Pelagos "Atlantic Sea", "in front of" the Pillars of Hercules (Στήλες του Ηρακλή) and facing a district called modern Gades or Gadira (Gadiron), a location that some modern Atlantis researchers associate with modern Gibraltar; however various locations have been proposed.Megatsunami
A megatsunami is a very large wave created by a large, sudden displacement of material into a body of water.
Megatsunamis have quite different features from other, more usual types of tsunamis. Most tsunamis are caused by underwater tectonic activity (movement of the earth's plates) and therefore occur along plate boundaries and as a result of earthquake and rise or fall in the sea floor, causing water to be displaced. Ordinary tsunamis have shallow waves out at sea, and the water piles up to a wave height of up to about 10 metres (33 feet) as the sea floor becomes shallow near land. By contrast, megatsunamis occur when a very large amount of material suddenly falls into water or anywhere near water (such as via a meteor impact), or are caused by volcanic activity. They can have extremely high initial wave heights of hundreds and possibly thousands of metres, far beyond any ordinary tsunami, as the water is "splashed" upwards and outwards by the impact or displacement. As a result, two heights are sometimes quoted for megatsunamis – the height of the wave itself (in water), and the height to which it surges when it reaches land, which depending upon the locale, can be several times larger.
Modern megatsunamis include the one associated with the 1883 eruption of Krakatoa (volcanic eruption), the 1958 Lituya Bay megatsunami (landslide into a bay), and the wave resulting from the Vajont Dam landslide (caused by human activity destabilizing sides of valley). Prehistoric examples include the Storegga Slide (landslide), and the Chicxulub, Chesapeake Bay and Eltanin meteor impacts.Montrose Basin
The Montrose Basin is part of the estuary of the South Esk forming a tidal basin near to the town of Montrose, Angus, on the east coast of Scotland.
The nature reserve in this embayment is internationally important for pink-footed geese, red knot and common redshank and is nationally important for common shelduck, wigeon and common eider ducks. It is also popular with mute swans, oystercatchers and northern lapwings as well as smaller birds. Breeding birds are preyed on by peregrine falcons and sparrowhawks. The visitor centre, run by the Scottish Wildlife Trust, is accessible from the A92 road.
The swans give the Basin its old, more poetic name, the "Sea of Swans".The Montrose Basin Heritage Society was formed in 1999 to bring together information about the basin, including its history and archaeology.
The Basin has been exploited for its seafood. At one time Montrose was Scotland's second largest exporter of salmon; and mussel cultivation gave it the largest mussel beds in the country during the 19th and early 20th centuries. Eels have also been an important catch.
The Montrose Basin was hit by a tsunami in 6100 BC, generated by the massive underwater Storegga Slide, in Norway. It was 70 feet (21 m) high when it hit the basin, with the waters travelling inland as far as Forfar.Norwegian Sea
The Norwegian Sea (Norwegian: Norskehavet) is a marginal sea in the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a submarine ridge running between Iceland and the Faroe Islands. To the north, the Jan Mayen Ridge separates it from the Greenland Sea.
Unlike many other seas, most of the bottom of the Norwegian Sea is not part of a continental shelf and therefore lies at a great depth of about two kilometres on average. Rich deposits of oil and natural gas are found under the sea bottom and are being explored commercially, in the areas with sea depths of up to about one kilometre. The coastal zones are rich in fish that visit the Norwegian Sea from the North Atlantic or from the Barents Sea (cod) for spawning. The warm North Atlantic Current ensures relatively stable and high water temperatures, so that unlike the Arctic seas, the Norwegian Sea is ice-free throughout the year. Recent research has concluded that the large volume of water in the Norwegian Sea with its large heat absorption capacity is more important as a source of Norway's mild winters than the Gulf Stream and its extensions.Prehistoric tsunamis
Prehistoric tsunamis are tsunamis and so-called "megatsunamis" that occurred before recorded history. The events have been identified through oral tradition and/or geological evidence. Those events that have been identified through contemporary records are listed as historic tsunamis.Submarine landslide
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 (gravity and other factors) 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.Timeline of environmental history
The timeline lists events in the external environment that have influenced events in human history. This timeline is for use with the article on environmental determinism.
For the history of humanity's influence on the environment, and humanity's perspective on this influence, see timeline of the history of environmentalism.
See List of periods and events in climate history for a timeline list focused on climate.Tollmann's bolide hypothesis
Tollmann's bolide hypothesis is a hypothesis presented by Austrian paleontologist Edith Kristan-Tollmann and geologist Alexander Tollmann in 1994. The hypothesis postulates that one or several bolides (asteroids or comets) struck the Earth around 7640 ± 200 years BCE, with a much smaller one approximately 3150 ± 200 BCE. The hypothesis tries to explain early Holocene extinctions and possibly legends of the Universal Deluge.The claimed evidence for the event includes stratigraphic studies of tektites, dendrochronology, and ice cores (from Camp Century, Greenland) containing hydrochloric acid and sulfuric acid (indicating an energetic ocean strike) as well as nitric acids (caused by extreme heating of air).
Christopher Knight and Robert Lomas in their book, Uriel's Machine, argue that the 7640 BCE evidence is consistent with the dates of formation of a number of extant salt flats and lakes in dry areas of North America and Asia. They argue that these lakes are the remains of multiple-kilometer-high waves that penetrated deeply into continents as the result of oceanic strikes that they proposed occurred. Research by Quaternary geologists, palynologists and others has been unable to confirm the validity of the hypothesis and proposes more frequently occurring geological processes for some of the data used for the hypothesis. Dating of ice cores and Australasian tektites has shown long time span differences between the proposed impact times and the impact ejecta products.Tsunami
A tsunami ( (t)soo-NAH-mee, (t)suu-; from Japanese: 津波, lit. 'harbour wave', pronounced [tsɯnami]) or tidal wave 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 (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 generated by the gravitational pull of the Moon and the Sun, a tsunami is generated by the displacement of water.
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 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 "internal 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 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; accurately forecasting the passage of tsunamis across the oceans; and forecasting how tsunami waves interact with shorelines.Tsunamis affecting the British Isles
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.