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Natural phenomena

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2004 Indian Ocean earthquake and tsunami

The 2004 Indian Ocean earthquake occurred at 00:58:53 UTC on 26 December, with an epicentre off the west coast of northern Sumatra. It was an undersea megathrust earthquake that registered a magnitude of 9.1–9.3 Mw, reaching a Mercalli intensity up to IX in certain areas. The earthquake was caused by a rupture along the fault between the Burma Plate and the Indian Plate.

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An earthquake is the shaking of the surface of the Earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to toss people around and destroy whole cities. The seismicity, or seismic activity, of an area is the frequency, type and size of earthquakes experienced over a period of time. The word tremor is also used for non-earthquake seismic rumbling.

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Hurricane Katrina

Hurricane Katrina was an extremely destructive and deadly Category 5 hurricane that struck the Gulf Coast of the United States in August 2005, causing catastrophic damage from central Florida to eastern Texas. Subsequent flooding, caused largely as a result of fatal engineering flaws in the flood protection system around the city of New Orleans, precipitated most of the loss of lives. The storm was the third major hurricane of the record-breaking 2005 Atlantic hurricane season, as well as the third most intense tropical cyclone on record to make landfall in the United States, behind only the 1935 Labor Day hurricane and Hurricane Camille in 1969.

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A tsunami or tidal wave, also known as a seismic sea 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, 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.

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Natural disaster

A natural disaster is a major adverse event resulting from natural processes of the Earth; examples are floods, hurricanes, tornadoes, volcanic eruptions, earthquakes, tsunamis, and other geologic processes. A natural disaster can cause loss of life or property damage, and typically leaves some economic damage in its wake, the severity of which depends on the affected population's resilience, or ability to recover and also on the infrastructure available.

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2011 Tōhoku earthquake and tsunami

The 2011 earthquake off the Pacific coast of Tōhoku was a magnitude 9.0–9.1 (Mw) undersea megathrust earthquake off the coast of Japan that occurred at 14:46 JST on Friday 11 March 2011, with the epicentre approximately 70 kilometres (43 mi) east of the Oshika Peninsula of Tōhoku and the hypocenter at an underwater depth of approximately 29 km (18 mi). The earthquake is often referred to in Japan as the Great East Japan Earthquake and is also known as the 2011 Tōhoku earthquake, and the 3.11 earthquake. It was the most powerful earthquake ever recorded in Japan, and the fourth most powerful earthquake in the world since modern record-keeping began in 1900. The earthquake triggered powerful tsunami waves that reached heights of up to 40.5 metres (133 ft) in Miyako in Tōhoku's Iwate Prefecture, and which, in the Sendai area, traveled up to 10 km (6 mi) inland. The earthquake moved Honshu 2.4 m (8 ft) east, shifted the Earth on its axis by estimates of between 10 cm (4 in) and 25 cm (10 in), increased earth's rotational speed by 1.8 µs per day, and generated infrasound waves detected in perturbations of the low-orbiting GOCE satellite. Initially, the earthquake caused sinking of part of Honshu's Pacific coast by up to roughly a metre, but after about three years, the coast rose back and kept on rising to exceed its original height.

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Chemtrail conspiracy theory

The chemtrail conspiracy theory is based on the erroneous belief that long-lasting condensation trails, called "chemtrails" by proponents, consist of chemical or biological agents left in the sky by high-flying aircraft and deliberately sprayed for purposes undisclosed to the general public. Believers in the conspiracy theory argue that normal contrails dissipate relatively quickly and contrails that do not dissipate must contain additional substances. Those who subscribe to the theory speculate that the purpose of the chemical release may be solar radiation management, weather modification, psychological manipulation, human population control, or biological or chemical warfare and that the trails are causing respiratory illnesses and other health problems.

Nature and flora, Science

Tropical cyclone

A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; while in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms".

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A tornado is a rapidly rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. The windstorm is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 110 miles per hour (180 km/h), are about 250 feet (80 m) across, and travel a few miles before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 miles per hour (480 km/h), are more than two miles (3 km) in diameter, and stay on the ground for dozens of miles.

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A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

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Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. The criteria can at times be ambiguous and may or may not define viruses, viroids, or potential synthetic life as "living". Biology is the science concerned with the study of life.

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A waterspout is an intense columnar vortex that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus cloud. In the common form, it is a non-supercell tornado over water.

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A flood is an overflow of water that submerges land that is usually dry. The European Union (EU) Floods Directive defines a flood as a covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health.

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In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within the smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars and Neptune. Cyclogenesis describes the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.

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Extraterrestrial life

Extraterrestrial life, also called alien life, is life that occurs outside of Earth and that probably did not originate from Earth. These hypothetical life forms may range from simple prokaryotes to beings with civilizations far more advanced than humanity. The Drake equation speculates about the existence of intelligent life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as exobiology.