113-498: The Mauna Loa Observatory ( MLO ) is an atmospheric baseline station on Mauna Loa , on the island of Hawaii , located in the U.S. state of Hawaii . The Mauna Loa Observatory was founded on June 28th 1956 as part of the US Weather Bureau . It was established on the northern flank of Mauna Loa at 11,134 ft after 1951-1954 efforts were unable to maintain a summit observatory at 13,453 ft. The Mauna Loa Observatory
226-465: A cave . They have been important to humans as a place of shelter since the dawn of humanity. Craters are depressions in the ground, but unlike caves, they do not provide shelter or extend underground . There are many kinds of craters, such as impact craters , volcanic calderas , and isostatic depressions . Karst processes can create both solution caves , the most frequent cave type, and craters, as seen in karst sinkholes . The pedosphere
339-434: A habitat refers to the environment where a given species or population of organisms lives. Biomes may span more than one continent, and contain a variety of ecosystems and habitats. Land plants evolved from green algae , and are called embryophytes . They include trees , shrubs , ferns , grass , moss , and flowers . Most plants are vascular plants , meaning that their tissues distribute water and minerals throughout
452-435: A boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone that is isothermal with height. Although variations do occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface. Thus, the lowest part of the troposphere (i.e. Earth's surface)
565-623: A coastline may be impacted by the tides , caused by changes in gravitational forces on larger bodies of water. Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity . On land, they harbour important ecosystems such as freshwater or estuarine wetlands , which are important for bird populations and other terrestrial animals. In wave-protected areas they harbor saltmarshes , mangroves or seagrasses , all of which can provide nursery habitat for finfish, shellfish , and other aquatic species. Rocky shores are usually found along exposed coasts and provide habitat for
678-505: A factor of 1/ e (0.368) every 7.64 km (25,100 ft), (this is called the scale height ) -- for altitudes out to around 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account. At heights over 100 km, an atmosphere may no longer be well mixed. Then each chemical species has its own scale height. In summary,
791-592: A habitat for soil organisms , a recycling system for nutrients and organic wastes , a regulator of water quality , a modifier of atmospheric composition , and a medium for plant growth , making it a critically important provider of ecosystem services . Since soil has a tremendous range of available niches and habitats , it contains a prominent part of the Earth's genetic diversity . A gram of soil can contain billions of organisms, belonging to thousands of species, mostly microbial and largely still unexplored. Soil
904-455: A large area, it can influence climate and weather patterns. The terrain of a region largely determines its suitability for human settlement: flatter alluvial plains tend to have better farming soils than steeper, rockier uplands. Elevation is defined as the vertical distance between an object and sea level, while altitude is defined as the vertical distance from an object to Earth's surface. The elevation of Earth's land surface varies from
1017-491: A large elevation difference between the highest and lowest points would be deemed "high relief". Most land has relatively low relief. The change in elevation between two points of the terrain is called a slope or gradient. A topographic map is a form of terrain cartography which depicts terrain in terms of its elevation, slope, and the orientation of its landforms. It has prominent contour lines , which connect points of similar elevation, while perpendicular slope lines point in
1130-514: A layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation (UV) from the Sun by the ozone layer, which restricts turbulence and mixing. Although the temperature may be −60 °C (−76 °F; 210 K) at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C. The stratospheric temperature profile creates very stable atmospheric conditions, so
1243-539: A long time to cause noticeable changes in the landscape—for example, the Grand Canyon was created over the past 70 million years by the Colorado River , which scientists estimate continues to erode the canyon at a rate of 0.3 meters (1 foot) every 200 years. However, humans have caused erosion to be 10–40 times faster than normal, causing half the topsoil of the surface of Earth's land to be lost within
SECTION 10
#17327728797151356-485: A million miles away, were found to be reflected light from ice crystals in the atmosphere. When light passes through Earth's atmosphere, photons interact with it through scattering . If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow, there
1469-518: A role in the regional and global climate. Densely populated cities are warmer and create urban heat islands that have effects on the precipitation, cloud cover , and temperature of the region. A landform is a natural or manmade land feature. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography . Landforms include hills , mountains , canyons , and valleys , as well as shoreline features such as bays , capes , and peninsulas . The shoreline
1582-421: A set of practices called sustainable land management . A biome is an area "characterized by its vegetation, soil, climate, and wildlife ." There are five major types of biomes on land: grasslands, forests, deserts, tundras, and freshwater. Other types of biomes include shrublands, wetlands, and polar ice caps . An ecosystem refers to the interaction between organisms within a particular environment, and
1695-746: A solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil is a three- state system of solids, liquids, and gases. Soil is a product of several factors: the influence of climate , relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering and erosion . Given its complexity and strong internal connectedness , soil ecologists regard soil as an ecosystem . Soil acts as an engineering medium,
1808-455: A steady growth to the present-day forms or, more likely, a rapid growth early in Earth history followed by a long-term steady continental area. Continents are formed by plate tectonics , a process ultimately driven by the continuous loss of heat from the Earth's interior. On time scales lasting hundreds of millions of years, the supercontinents have formed and broken apart three times. Roughly 750 mya (million years ago), one of
1921-433: A wide range of sessile animals (e.g. mussels , starfish , barnacles ) and various kinds of seaweeds . Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 meters (3.3–164.0 feet). According to a United Nations atlas, 44% of all people live within 150 km (93 mi) of the sea. Because of their importance in society and high concentration of population,
2034-557: Is 14 °C (57 °F; 287 K) or 15 °C (59 °F; 288 K), depending on the reference. 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 5.1480×10 kg (1.135×10 lb), about 2.5% less than would be inferred from
2147-442: Is a major component of the Earth's ecosystem. The world's ecosystems are impacted in far-reaching ways by the processes carried out in the soil, with effects ranging from ozone depletion and global warming to rainforest destruction and water pollution . With respect to Earth's carbon cycle , soil acts as an important carbon reservoir , and it is potentially one of the most reactive to human disturbance and climate change. As
2260-470: Is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character. The composition of land is not uniform across the Earth, varying between locations and between strata within the same location. The most prominent components of upper continental crust include silicon dioxide , aluminium oxide , and magnesium . The continental crust consists of lower density material such as
2373-408: Is about 1.2 kg/m (1.2 g/L, 0.0012 g/cm ). 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
SECTION 20
#17327728797152486-414: Is about 28.946 or 28.96 g/mol. This is decreased when the air is humid. The relative concentration of gases remains constant until about 10,000 m (33,000 ft). In general, air pressure and density decrease with altitude in the atmosphere. However, temperature has a more complicated profile with altitude and may remain relatively constant or even increase with altitude in some regions (see
2599-442: Is also used in wetland ecology, where "upland" plants indicate an area that is not a wetland. In addition, the term moorland refers to upland shrubland biomes with acidic soils, while heathlands are lowland shrublands with acidic soils. Geomorphology refers to the study of the natural processes that shape land's surface, creating landforms. Erosion and tectonics , volcanic eruptions , flooding , weathering , glaciation ,
2712-529: Is also used more generally, as in Persian rigestân ( ریگستان ) "place of sand, desert", golestân ( گلستان ) "place of flowers, garden", gurestân ( گورستان ) "graveyard, cemetery", and Hindustân ( هندوستان ) "land of the Indo people". The study of land and its history in general is called geography . Mineralogy is the study of minerals, and petrology is the study of rocks. Soil science
2825-488: Is an island , and a chain of islands is an archipelago . The smaller the island, the larger the percentage of its land area will be adjacent to the water, and subsequently will be coast or beach. Islands can be formed by a variety of processes. The Hawaiian islands , for example, even though they are not near a plate boundary, formed from isolated volcanic activity . Atolls are ring-shaped islands made of coral , created when subsidence causes an island to sink beneath
2938-442: Is because clouds (H 2 O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations. The greenhouse effect is directly related to this absorption and emission effect. Some gases in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these are CO 2 and H 2 O. The refractive index of air
3051-1429: Is called paleoclimatology . 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 air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). The remaining gases are often referred to as trace gases, among which are other greenhouse gases , principally carbon dioxide, methane, nitrous oxide, and ozone. Besides argon, other noble gases , neon , helium , krypton , and xenon are also present. Filtered air includes trace amounts of many other chemical compounds . Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores , sea spray , and volcanic ash . Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO 2 ) may be derived from natural sources or from industrial air pollution. Mole fraction
3164-644: Is called the shoreline . The word land is derived from Old English , from the Proto-Germanic word * landą , "untilled land", and then the Proto-Indo-European * lendʰ- , especially in northern regions that were home to languages like Proto-Celtic and Proto-Slavic . Examples include Old Irish land , "land, plot, church building" and Old Irish ithlann , "threshing floor", and Old East Slavic ljadina "wasteland, weeds". A country or nation may be referred to as
3277-447: Is close to, but just greater than, 1. Systematic variations in the refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers on board ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of Earth's surface. The refractive index of air depends on temperature, giving rise to refraction effects when
3390-472: Is located below the observatory site and is managed by Hawaii Volcanoes National Park . It passes through State of Hawaii conservation land managed by the Hawaii Department of Land and Natural Resources . The access road was obstructed by lava flow from the 2022 eruption of Mauna Loa . As of February 2023, deposits continue to block vehicular access to the observatory. Utility lines that powered
3503-477: Is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometres without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space . These free-moving particles follow ballistic trajectories and may migrate in and out of
Mauna Loa Observatory - Misplaced Pages Continue
3616-445: Is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering , shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal before reaching your eye. Much of
3729-418: Is often defined as the solid, dry surface of Earth. The word land may also collectively refer the collective natural resources of Earth, including its land cover , rivers , shallow lakes , its biosphere , the lowest layer of the atmosphere ( troposphere ), groundwater reserves, and the physical results of human activity on land, such as architecture and agriculture. The boundary between land and sea
3842-459: Is pushed upwards, or subductional events, where Earth's crust is pushed into the mantle, causing the crust to melt, rise due to its low density, and solidify into hardened rock, thickening the crust. A plateau , also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side, creating steep cliffs or escarpments . Both volcanic activity such as
3955-513: Is so tenuous that some scientists consider it to be part of interplanetary space rather than part of the atmosphere). It extends from the thermopause (also known as the "exobase") at the top of the thermosphere to a poorly defined boundary with the solar wind and interplanetary medium . The altitude of the exobase varies from about 500 kilometres (310 mi; 1,600,000 ft) to about 1,000 kilometres (620 mi) in times of higher incoming solar radiation. The upper limit varies depending on
4068-481: Is sometimes referred to as volume fraction ; these are identical for an ideal gas only. ppm: parts per million by molecular count The concentration of CO 2 has been increasing in recent decades , as has that of CH 4 . Water vapor is about 0.25% by mass over full atmosphere Water vapor varies significantly locally The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction,
4181-448: Is the interface between the land and the ocean . It migrates each day as tides rise and fall, and moves over long periods of time as sea levels change. The shore extends from the low tide line to the highest elevation that can be reached by storm waves, and the coast stretches out inland until the point where ocean-related features are no longer found. When land is in contact with bodies of water, it can be eroded. The weathering of
4294-461: Is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator , with some variation due to weather. The troposphere is bounded above by the tropopause ,
4407-399: Is the outermost layer of Earth's continental surface and is composed of soil and subject to soil formation processes . Below it, the lithosphere encompasses both Earth's crust and the uppermost layer of the mantle . The lithosphere rests, or "floats", on top of the mantle below it via isostasy . Above the solid ground, the troposphere and humans' use of land can be considered layers of
4520-467: Is the study of soils, encompassing the sub-disciplines of pedology , which focuses on soil formation, and edaphology , which focuses on the relationship between soil and life. The earliest material found in the Solar System is dated to 4.5672 ± 0.0006 bya (billion years ago); therefore, the Earth itself must have been formed by accretion around this time. The formation and evolution of
4633-465: Is thicker than oceanic crust , and it is far more varied in terms of composition. About 31% of this continental crust is submerged in shallow water, forming continental shelves. Land provides many ecosystem services , such as mitigating climate change, regulating water supply through drainage basins and river systems, and supporting food production. Land resources are finite, which has led to regulations intended to safeguard these ecosystem services, and
Mauna Loa Observatory - Misplaced Pages Continue
4746-412: Is too low to conduct a significant amount of energy to or from the skin. This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi). It is this layer where many of
4859-479: Is typically the warmest section of the troposphere. This promotes vertical mixing (hence, the origin of its name in the Greek word τρόπος, tropos , meaning "turn"). The troposphere contains roughly 80% of the mass of Earth's atmosphere. The troposphere is denser than all its overlying layers because a larger atmospheric weight sits on top of the troposphere and causes it to be most severely compressed. Fifty percent of
4972-725: The Earth 's planetary surface (both lands and oceans ), known collectively as air , with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes ), all retained by Earth's gravity . The atmosphere serves as a protective buffer between the Earth's surface and outer space , shields the surface from most meteoroids and ultraviolet solar radiation , keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night ) through heat retention ( greenhouse effect ), redistributes heat and moisture among different regions via air currents , and provides
5085-638: The Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind . The atmosphere and oceans of the Earth continuously shape the land by eroding and transporting solids on the surface. Earth's crust formed when the molten outer layer of the planet Earth cooled to form a solid mass as the accumulated water vapour began to act in the atmosphere. Once land became capable of supporting life, biodiversity evolved over hundreds of millions of years, expanding continually except when punctuated by mass extinctions. The two models that explain land mass propose either
5198-582: The F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months, otherwise, orbital decay will occur resulting in a return to Earth. Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as 700–800 km. 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
5311-549: The Keeling Curve , is the foundational study in the composition and behavior of greenhouse gases in the atmosphere. Other early research at the observatory included measurements of cosmic radiation, the atmosphere of Mars, atomic fallout, snow crystals, the solar corona, meteors, cosmic rays, and radio transmission. The International Geophysical Year enabled many of the early projects at the observatory to secure support and funding. The Mauna Loa Observatory has been part of
5424-517: The National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory ’s Baseline Observatory network since 1972. The observatory's location, far from continental sources of emissions and above the marine inversion layer , make it an ideal site for atmospheric monitoring. The absence of continental weather patterns, lack of vegetation, and a predictable diurnal wind pattern provide routine access to clean, well-mixed air from
5537-523: The biosphere . Human manipulation of the land, including agriculture and architecture , can also be considered part of land. Land is formed from the continental crust , the layer of rock on which soil . groundwater , and human and animal activity sits. Though modern terrestrial plants and animals evolved from aquatic creatures, Earth's first cellular life likely originated on land. Survival on land relies on fresh water from rivers, streams, lakes, and glaciers, which constitute only three percent of
5650-489: The chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules ), dry air contains 78.08% nitrogen , 20.95% oxygen , 0.93% argon , 0.04% carbon dioxide , and small amounts of other trace gases . Air also contains a variable amount of water vapor , on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature and atmospheric pressure vary with altitude . Within
5763-420: The evolution of life (particularly the photoautotrophs ). Recently, human activity has also contributed to atmospheric changes , such as climate change (mainly through deforestation and fossil fuel -related global warming ), ozone depletion and acid deposition . The atmosphere has a mass of about 5.15 × 10 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of
SECTION 50
#17327728797155876-588: The infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimetre to about eleven-metre waves. Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their " black body " emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example,
5989-433: The magnetosphere or the solar wind. Every second, the Earth loses about 3 kg of hydrogen, 50 g of helium, and much smaller amounts of other constituents. The exosphere is too far above Earth for meteorological phenomena to be possible. However, Earth's auroras —the aurora borealis (northern lights) and aurora australis (southern lights)—sometimes occur in the lower part of the exosphere, where they overlap into
6102-402: The mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F ; 190 K ). Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can condense into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in
6215-515: The motherland , fatherland , or homeland of its people. Many countries and other places have names incorporating the suffix -land (e.g. England , Greenland , and New Zealand ). The equivalent suffix -stan from Indo-Iranian , ultimately derived from the Proto-Indo-Iranian * sthāna- , is also present in many country and location names, such as Pakistan , Afghanistan , and others throughout Central Asia . The suffix
6328-428: The temperature section). Because the general pattern of the temperature/altitude profile, or lapse rate , is constant and measurable by means of instrumented balloon soundings , the temperature behavior provides a useful metric to distinguish atmospheric layers. This atmospheric stratification divides the Earth's atmosphere into five main layers: The exosphere is the outermost layer of Earth's atmosphere (though it
6441-511: The tropopause . This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft). The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level . It contains the ozone layer , which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines
6554-434: The upwelling of magma and extrusion of lava, or erosion of mountains caused from water, glaciers, or aeolian processes, can create plateaus. Plateaus are classified according to their surrounding environment as intermontane , piedmont , or continental . A few plateaus may have a small flat top while others are wider. Buttes are smaller, with less extrusive and more intrusive igneous rock, while plateaus or highlands are
6667-654: The whale , that evolved from terrestrial mammals back to an aquatic lifestyle. Many megafauna of the past, such as non-avian dinosaurs , have become extinct due to extinction events, e.g. the Quaternary extinction event . Land is "deeply intertwined with human development." It is a crucial resource for human survival, humans depend on land for subsistence, and can develop strong symbolic attachments to it. Access to land can determine "survival and wealth," particularly in developing countries, giving rise to complex power relationships in production and consumption. Most of
6780-432: The Earth's crust. About 30 percent of land has a dry climate, due to losing more water through evaporation than it gains from precipitation . Since warm air rises, this generates winds, though Earth's rotation and uneven sun distribution also play a part. Land is commonly defined as the solid, dry surface of Earth. It can also refer to the collective natural resources that the land holds, including rivers , lakes , and
6893-573: The Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply. The various layers of Earth's ionosphere , important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within
SECTION 60
#17327728797157006-579: The Solar System bodies occurred in tandem with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disc , out of which the planets then grow (in tandem with the star). A nebula contains gas, ice grains and dust (including primordial nuclides ). In nebular theory , planetesimals begin to form as particulate matter accumulates by cohesive clumping and then by gravity. The primordial Earth's assembly took 10– 20 myr . By 4.54 ± 0.04 bya ,
7119-459: The Sun is approximately 6,000 K (5,730 °C ; 10,340 °F ), its radiation peaks near 500 nm, and is visible to the human eye. Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans. Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This
7232-420: The aptly-named thermosphere above 90 km. Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile (see illustration to the right), and does not mirror altitudinal changes in density or pressure. The density of air at sea level
7345-421: The atmosphere also cools by emitting radiation, as discussed below. The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity , allowing the transmission of only certain bands of light. The optical window runs from around 300 nm ( ultraviolet -C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to
7458-399: The atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds . The mesosphere is also
7571-489: The atmosphere based on characteristics such as temperature and composition, namely the troposphere , stratosphere , mesosphere , thermosphere (formally the ionosphere ) and exosphere . The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics . Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann . The study of historic atmosphere
7684-404: The atmosphere, air suitable for use in photosynthesis by terrestrial plants and respiration of terrestrial animals is found only within 12 kilometres (7.5 mi) from the ground. Earth's early atmosphere consisted of accreted gases from the solar nebula , but the atmosphere changed significantly over time, affected by many factors such as volcanism , impact events , weathering and
7797-637: 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 weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea level density (about 1.2 kg per m ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 km (27,900 ft). Air pressure actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by
7910-414: The blue light has been scattered out, leaving the red light in a sunset. Different molecules absorb different wavelengths of radiation. For example, O 2 and O 3 absorb almost all radiation with wavelengths shorter than 300 nanometres . Water (H 2 O) absorbs at many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. This heats the atmosphere, but
8023-506: The climate change impacts on habitats and biodiversity, as well as natural resources, in the target areas. Land cover change detection and mapping is a key component of interdisciplinary land change science , which uses it to determine the consequences of land change on climate. Land change modeling is used to predict and analyze changes in land cover and use. Soil is a mixture of organic matter , minerals , gases , liquids , and organisms that together support life . Soil consists of
8136-636: The coast is important for major parts of the global food and economic system, and they provide many ecosystem services to humankind. For example, important human activities happen in port cities . Coastal fisheries for commercial, recreational, and subsistence purposes, and aquaculture are major economic activities and provide jobs, livelihoods, and protein for the majority of coastal human populations. Other coastal spaces like beaches and seaside resorts generate economic activity through tourism . Marine coastal ecosystems can also provide protection against sea level rise and tsunamis . In many countries,
8249-419: The coastal mangrove is the primary source of wood for fuel (e.g. charcoal) and building materials. Coastal ecosystems have a much higher capacity for carbon sequestration than many terrestrial ecosystems , and as such can play a critical role in the near future to help mitigate climate change effects by uptake of atmospheric anthropogenic carbon dioxide . A subcontinental area of land surrounded by water
8362-415: The definition. Various authorities consider it to end at about 10,000 kilometres (6,200 mi) or about 190,000 kilometres (120,000 mi)—about halfway to the moon, where the influence of Earth's gravity is about the same as radiation pressure from sunlight. The geocorona visible in the far ultraviolet (caused by neutral hydrogen) extends to at least 100,000 kilometres (62,000 mi). This layer
8475-580: The direction of the steepest slope. Hypsometric tints are colors placed between contour lines to indicate elevation relative to sea level . A difference between uplands, or highlands , and lowlands is drawn in several earth science fields. In river ecology, " upland " rivers are fast-moving and colder than "lowland" rivers, encouraging different species of fish and other aquatic wildlife to live in these habitats. For example, nutrients are more present in slow-moving lowland rivers, encouraging different species of macrophytes to grow there. The term "upland"
8588-981: The earliest known supercontinents, Rodinia , began to break apart. The continents later recombined to form Pannotia , 600– 540 mya , then finally Pangaea , which also broke apart 180 mya . A continuous area of land surrounded by an ocean is called a landmass. Although it is most often written as one word to distinguish it from the usage "land mass"—the measure of land area—it may also be written as two words. There are four major continuous landmasses on Earth: Afro-Eurasia , America (landmass) , Antarctica , and Australia (landmass) , which are subdivided into continents. Up to seven geographical regions are commonly regarded as continents. Ordered from greatest to least land area, these continents are Asia , Africa , North America , South America , Antarctica , Europe , and Australia . Terrain refers to an area of land and its features. Terrain affects travel, mapmaking, ecosystems, and surface water flow and distribution. Over
8701-416: The facility were also damaged, further impeding operation. Temporary solar power has been established, which allows the observatory to operate at approximately 33 percent of its full capacity. This is as renovations are underway to upgrade the facility with new power distribution infrastructure. Earth%27s atmosphere The atmosphere of Earth is composed of a layer of gas mixture that surrounds
8814-430: The free troposphere. The observatory's reading of a historic high in its daily recording of carbon dioxide emissions – 400 parts per million, in 2015 – was referenced by Pope Francis in his apostolic exhortation on the climate crisis , Laudate Deum . In addition to NOAA-GML projects the observatory campus remains host to projects from partner institutions, governmental organizations, and universities from around
8927-434: The gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule (of oxygen , for example) travels an average of 1 kilometre (0.62 mi; 3300 ft) between collisions with other molecules. Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density
9040-490: The geological continents and the areas of shallow seabed close to their shores, known as continental shelves . This layer is sometimes called sial because its bulk composition is richer in aluminium silicate and has a lower density compared to the oceanic crust , called sima which is richer in magnesium silicate . Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity ), there
9153-409: The growth of coral reefs , and meteorite impacts are among the processes that constantly reshape Earth's surface over geological time . Erosion transports one part of land to another via natural processes, such as wind , water, ice , and gravity . In contrast, weathering wears away rock and other solid land without transporting the land somewhere else. Natural erosional processes usually take
9266-402: The harvest of crops. Floodplains provided agricultural land for some of the earliest civilizations . Erosion is often a main driver for the creation of plains and valleys, with rift valleys being a noticeable exception. Fjords are glacial valleys that can be thousands of meters deep, opening out to the sea. Any natural void in the ground which can be entered by a human can be considered
9379-623: The igneous rocks granite and andesite . Less common is basalt , a denser volcanic rock that is the primary constituent of the ocean floors . Sedimentary rock is formed from the accumulation of sediment that becomes buried and compacted together . Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the crust. The most abundant silicate minerals on Earth's surface include quartz , feldspars , amphibole , mica , pyroxene and olivine . Common carbonate minerals include calcite (found in limestone ) and dolomite . The rock that makes up land
9492-476: The land is divided into two major categories: Mountain ranges and relatively flat interiors called cratons . Both form over millions of years through plate tectonics . Streams – a major part of Earth's water cycle – shape the landscape , carve rocks, transport sediments, and replenish groundwater. At high elevations or latitudes , snow is compacted and recrystallized over hundreds or thousands of years to form glaciers, which can be so heavy that they warp
9605-489: The land will influence how much solar radiation reaches its surface. High latitudes receive less solar radiation than low latitudes. The land's topography is important in creating and transforming airflow and precipitation . Large landforms, such as mountain ranges, can divert wind energy and make air parcels less dense and therefore able to hold less heat. As air rises, this cooling effect causes condensation and precipitation. Different types of land cover will influence
9718-425: The land's albedo , a measure of the solar radiation that is reflected, rather than absorbed and transferred to Earth. Vegetation has a relatively low albedo, meaning that vegetated surfaces are good absorbers of the sun's energy. Forests have an albedo of 10–15 percent while grasslands have an albedo of 15–20 percent. In comparison, sandy deserts have an albedo of 25–40 percent. Land use by humans also plays
9831-705: The land. Land cover refers to the material physically present on the land surface, for example, woody crops, herbaceous crops, barren land, and shrub-covered areas. Artificial surfaces (including cities) account for about a third of a percent of all land. Land use refers to human allocation of land for various purposes, including farming, ranching, and recreation (e.g. national parks); worldwide, there are an estimated 16.7 million km (6.4 million sq mi) of cropland, and 33.5 million km (12.9 million sq mi) of pastureland. Land cover change detection using remote sensing and geospatial data provides baseline information for assessing
9944-403: The layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft . The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by
10057-465: The low point of −418 m (−1,371 ft) at the Dead Sea , to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount Everest. The mean height of land above sea level is about 797 m (2,615 ft), with 98.9% of dry land situated above sea level. Relief refers to the difference in elevation within a landscape; for example, flat terrain would have "low relief", while terrain with
10170-482: The mass of Earth's atmosphere is distributed approximately as follows: By comparison, the summit of Mount Everest is at 8,848 m (29,029 ft); commercial airliners typically cruise between 10 and 13 km (33,000 and 43,000 ft) where the lower density and temperature of the air improve fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft). Even above
10283-441: The ocean surface and leaves a ring of reefs around it. Mountains are features that usually rise at least 300 metres (980 ft) higher than the surrounding terrain. The formation of mountain belts is called orogenesis, and results from plate tectonics . For example, where a plate at a convergent plate boundary pushes one plate above the other, mountains could be formed by either collisional events, such that Earth's crust
10396-514: The orbital decay of satellites. The average mass of the atmosphere is about 5 quadrillion (5 × 10 ) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research , "The total mean mass of the atmosphere is 5.1480 × 10 kg with an annual range due to water vapor of 1.2 or 1.5 × 10 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than
10509-504: The outer part of the crust . Land plays an important role in Earth's climate system , being involved in the carbon cycle , nitrogen cycle , and water cycle . One-third of land is covered in trees, another third is used for agriculture , and one-tenth is covered in permanent snow and glaciers . The remainder consists of desert , savannah , and prairie . Land terrain varies greatly, consisting of mountains, deserts, plains, plateaus, glaciers, and other landforms . In physical geology,
10622-405: The past 150 years. Plate tectonics refers to the theory that Earth's lithosphere is divided into "tectonic plates" that move over the mantle. This results in continental drift , with continents moving relative to each other. The scientist Alfred Wegener first hypothesized the theory of continental drift in 1912. More researchers gradually developed his idea throughout the 20th century into
10735-408: The planet warms, it has been predicted that soils will add carbon dioxide to the atmosphere due to increased biological activity at higher temperatures, a positive feedback (amplification). This prediction has, however, been questioned on consideration of more recent knowledge on soil carbon turnover. Continental crust is the layer of igneous , sedimentary , and metamorphic rocks that forms
10848-433: The plant. Through photosynthesis , most plants nourish themselves from sunlight and water, breathing in carbon dioxide and breathing out oxygen. Between 20 and 50% of oxygen is produced by land vegetation. Unlike plants, terrestrial animals are not a monophyletic group —that is, a group including all terrestrial animals does not encompass all lineages from a common ancestor . This is because there are organisms, such as
10961-526: The previous estimate. The mean mass of water vapor is estimated as 1.27 × 10 kg and the dry air mass as 5.1352 ±0.0003 × 10 kg." 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
11074-441: The primordial Earth had formed. Earth's atmosphere and oceans were formed by volcanic activity and outgassing that included water vapour . The origin of the world's oceans was condensation augmented by water and ice delivered by asteroids , protoplanets , and comets . In this model , atmospheric " greenhouse gases " kept the oceans from freezing while the newly formed Sun was only at 70% luminosity . By 3.5 bya ,
11187-422: The satellites orbiting the Earth are present. The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level. Temperatures drop with increasing altitude to
11300-447: The stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft . The troposphere
11413-453: The surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space . The Kármán line , at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in
11526-449: The temperature gradient is large. An example of such effects is the mirage . Land Land , also known as dry land , ground , or earth , is the solid terrestrial surface of Earth not submerged by the ocean or another body of water . It makes up 29.2% of Earth's surface and includes all continents and islands . Earth's land surface is almost entirely covered by regolith , a layer of rock , soil , and minerals that forms
11639-444: 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 the Sun by the dioxygen and ozone gas in this region. Still another region of increasing temperature with altitude occurs at very high altitudes, in
11752-442: The thermopause varies considerably due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase . The lower part of the thermosphere, from 80 to 550 kilometres (50 to 342 mi) above Earth's surface, contains the ionosphere . The temperature of the thermosphere gradually increases with height and can rise as high as 1500 °C (2700 °F), though
11865-429: The thermosphere. The exosphere contains many of the artificial satellites that orbit Earth. The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of
11978-419: The total mass of the atmosphere is located in the lower 5.6 km (3.5 mi; 18,000 ft) of the troposphere. Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate
12091-430: The tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer accessible by propeller-driven aircraft . Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties: The average temperature of the atmosphere at Earth's surface
12204-446: The water on Earth. The vast majority of human activity throughout history has occurred in habitable land areas supporting agriculture and various natural resources . In recent decades, scientists and policymakers have emphasized the need to manage land and its biosphere more sustainably, through measures such as restoring degraded soil , preserving biodiversity , protecting endangered species , and addressing climate change . Land
12317-701: The widely accepted theory of plate tectonics of today. Several key characteristics define modern understanding of plate tectonics. The place where two tectonic plates meet is called a plate boundary , with different geological phenomena occurring across different kinds of boundaries. For example, at divergent plate boundaries , seafloor spreading is usually seen, in contrast with the subduction zones of convergent or transform plate boundaries . Earthquakes and volcanic activity are common in all types of boundaries. Volcanic activity refers to any rupture in Earth's surface where magma escapes, therefore becoming lava . The Ring of Fire , containing two-thirds of
12430-512: The widest, and mesas are a general-sized plateau with horizontal bedrock strata . Wide, flat areas of land are called plains , which cover more than one-third of Earth's land area. When they occur as lowered areas between mountains, they can create valleys , canyons or gorges, and ravines . A plateau can be thought of as an elevated plain. Plains are known to have fertile soils and be important for agriculture due to their flatness supporting grasses suitable for livestock and facilitating
12543-466: The world's volcanos, and over 70% of Earth's seismological activity , comprises plate boundaries surrounding the Pacific Ocean . Earth's land interacts with and influences its climate heavily, since the land's surface heats up and cools down faster than air or water. Latitude , elevation , topography , reflectivity , and land use all have varying effects on climate. The latitude of
12656-505: The world. The Mauna Loa Solar Observatory and NSF's Global Oscillations Network Group ( GONG ) station share this site. The observatory site is also a temporary home to a cosmic microwave background observatory called YTLA . The observatory is located at the end of the Mauna Loa Observatory Access Road. Gated access to the observatory is managed by NOAA. The northern trailhead to the summit of Mauna Loa
12769-558: Was developed specifically to monitor solar, atmospheric and meteorological parameters in the free atmosphere. Establishment of a solar constant, routine weather observations, the determination of ozone and monitoring atmospheric circulation were early priorities. Continuous carbon dioxide measurements began in March of 1958 directed by Charles David Keeling from the Scripps Institute of Oceanography . The data set, referred to as
#714285