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The Mount Edziza volcanic complex (MEVC) is a group of volcanoes and associated lava flows in northwest British Columbia, Canada. Located on the Tahltan Highland, the MEVC has a broad, steep-sided lava plateau; its highest summit is 2,786 metres (9,140 feet). Its volcanoes formed over the last 7.5 million years during five cycles of magmatic ...
1989 Tiananmen Square protests and massacre. / 39.90333°N 116.39167°E / 39.90333; 116.39167. The Tiananmen Square protests, known in China as the June Fourth Incident, [1] [2] [a] were student-led demonstrations held in Tiananmen Square, Beijing, China, lasting from 15 April to 4 June 1989. After weeks of unsuccessful attempts between ...
- 15 April – 4 June 1989, (1 month, 2 weeks and 6 days)
- See Death toll
Water is an inorganic compound with the chemical formula H2O. It is a transparent, tasteless, odorless,[c] and nearly colorless chemical substance, and it is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent[19]). It is vital for all known forms of life, despite not ...
- Composition
- Stratification
- Physical Properties
- Optical Properties
- Circulation
- Evolution of Earth's Atmosphere
- Images from Space
- See Also
- External Links
The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid a...
In general, air pressure and density decrease with altitude in the atmosphere. However, the temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions (see the temperature section, below). Because the general pattern of the temperature/altitude profile, or lapse rate, ...
Pressure and thickness
The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00 Torr; 14.6959 psi; 760.00 mmHg). This is sometimes referred to as a unit of standard atmospheres (atm). Total atmospheric mass is 5.1480×1018 kg (1.135×1019 lb), about 2.5% less than would be inferred from the average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total...
Temperature
The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where the temperature stabilizes over a large vertical distance through the rest of the troposphere. In the stratosphere, starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by the capture of significant ultraviolet radiation from t...
Density and mass
The density of air at sea level is about 1.2 kg/m3 (1.2 g/L, 0.0012 g/cm3). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used to predict the orbital decay of satellites. The average mass of the atmosphere is...
Solar radiation (or sunlight) is the energy Earth receives from the Sun. Earth also emits radiation back into space, but at longer wavelengths that humans cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. In May 2017, glints of light, seen as twinkling from an orbiting satellite a million miles away,...
Atmospheric circulation is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed around Earth. The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant because it is determined by Earth's rotation rate and...
Earliest atmosphere
The first atmosphere consisted of gases in the solar nebula, primarily hydrogen. There were probably simple hydrides such as those now found in the gas giants (Jupiter and Saturn), notably water vapor, methane and ammonia.
Second atmosphere
Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced the next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases.A major part of carbon-dioxide emissions dissolved in water and reacted with metals such as calcium and magnesium during weathering of crustal rocks to form carbonates that were deposited as sediments. Water-related sediments have been found that date from as early as 3.8 billion...
Third atmosphere
The constant re-arrangement of continents by plate tectonics influences the long-term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2.4 billion years ago during the Great Oxygenation Event and its appearance is indicated by the end of the banded iron formations. Before this time, any oxygen produced by photosynthesis was consumed by the oxidation of reduced materials, notably i...
On October 19, 2015, NASA started a website containing daily images of the full sunlit side of Earth at https://epic.gsfc.nasa.gov/. The images are taken from the Deep Space Climate Observatory(DSCOVR) and show Earth as it rotates during a day.
Buchan, Alexander (1878). "Atmosphere" . Encyclopædia Britannica. Vol. III (9th ed.). pp. 28–36.The ocean is the body of salt water that covers approx. 70.8% of Earth.[8] In English, the term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided.[9] The following names describe five different areas of the ocean: Pacific, Atlantic, Indian, Antarctic/Southern, and Arctic.[10][11] The ...
Background Titanic on sea trials, 2 April 1912 At the time of her entry into service on 2 April 1912, the Titanic was the second of three Olympic-class ocean liners, and was the largest ship in the world.She and the earlier RMS Olympic were almost one and a half times the gross register tonnage of Cunard's RMS Lusitania and RMS Mauretania, the previous record holders, and were nearly 100 feet ...
Physical properties. Pure sodium hydroxide is a colorless crystalline solid that melts at 318 °C (604 °F) without decomposition and boils at 1,388 °C (2,530 °F). It is highly soluble in water, with a lower solubility in polar solvents such as ethanol and methanol. [14] Sodium hydroxide is insoluble in ether and other non-polar solvents.
