What is Nature?

What is Nature?

Nature, in the broadest sense, is equivalent to the natural worldphysical world, or material world. “Nature” refers to the phenomena of the physical world, and also to life in general. It ranges in scale from the subatomic to the cosmic.

The term “nature” may refer to living plants and animals, geological processes, weather, and physics, such as matter and energy. The term is often refers to the “natural environment” or wilderness—wild animals, rocks, forest, beaches, and in general areas that have not been substantially altered by humans, or which persist despite human intervention. For, example, manufactured objects and human interaction are generally not considered part of nature, unless qualified as, for example, “human nature” or “the whole of nature“. This more traditional concept of “nature” implies a distinction between natural and artificial elements of the Earth, with the artificial as that which has been brought into being by a human consciousness or a human mind.

Bachalpsee in the Swiss Alps; generally mountainous areas are less affected by human activity

Much attention has been given to preserving the natural characteristics of Hopetoun Falls, Australia, while maintaining visitor access.

Lightning strikes during the eruption of the huge Galunggung volcano in 1982

Etymology

The word nature is derived from the Latin word natura, or “essential qualities, innate disposition”, and literally means “birth”.[1] Natura was a Latin translation of the Greek word physis(φύσις), which correlated plants, animals, and other features of the world as developing of their own accord.[2][3] The concept of nature as a whole, the physical universe, is one of several expansions of the original notion; it began with certain core applications of the word φύσις by pre-Socratic philosophers, and has steadily gained currency ever since.

Earth

View of Earth, taken in 1972 by the Apollo 17 crew. This image is the only photograph of its kind to date, showing a fully sunlit hemisphere of the Earth.

Earth (or, “the earth”) is the only planet presently known to support life, and its natural features are the subject of many fields of scientific research. Within the solar system, it is third nearest to the sun; it is the largest terrestrial planet and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and a wide equatorial tropical to subtropical region.[4] Precipitation varies widely with location, from several metres of water per year to less than a millimetre. 71 percent of the Earth’s surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere.

Earth has evolved through geological and biological processes that have left traces of the original conditions. The outer surface is divided into several gradually migrating tectonic plates, which have changed relatively quickly several times. The interior remains active, with a thick layer of molten mantle and an iron-filled core that generates a magnetic field.

The atmospheric conditions have been significantly altered from the original conditions by the presence of life-forms,[5] which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods,[6] and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.[7][8]

Historical perspective

Plankton (Phylum Pediastrumboryanum) have existed on Earth for at least 2 billion years.[9]

Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other planets.[10] The moon formed roughly 20 million years later. Initially molten, the outer layer of the planet cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources.[11] The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago.[12]

Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a supercontinent. Roughly 750 million years ago, the earliest known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia which broke apart about 540 million years ago, then finally Pangaea, which broke apart about 180 million years ago.[13]

Land-based plants and fungi have been part of nature on Earth for about the past 400 million years. These have needed to adapt and move many times as the continents and climates changed.[14][15]

There is significant evidence, still being discussed among scientists, that a severe glacial action during the Neoproterozoic era covered much of the planet in a sheet of ice. This hypothesis has been termed the “Snowball Earth”, and it is of particular interest as it precedes the Cambrian explosion in which multicellular life forms began to proliferate about 530–540 million years ago.[16]

Since the Cambrian explosion there have been five distinctly identifiable mass extinctions.[17] The last mass extinction occurred some 65 million years ago, when a meteorite collision probably triggered the extinction of the non-avian dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life diversified.[18]

Several million years ago, a species of small African ape gained the ability to stand upright.[19] The subsequent advent of human life, and the development of agriculture and further civilization allowed humans to affect the Earth more rapidly than any previous life form, affecting both the nature and quantity of other organisms as well as global climate. By comparison, the oxygen catastrophe, produced by the proliferation of algae during the Siderian period, required about 300 million years to culminate.)

The present era is classified as part of a mass extinction event, the Holocene extinction event, the fastest ever to have occurred.[20][21] Some, such as E. O. Wilson of Harvard University, predict that human destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years.[22] The extent of the current extinction event is still being researched, debated and calculated by biologists.[23]

Geology

Three types of plate boundary.

Geology (from Greek: γη, , “earth”; and λόγος, logos, “speech” lit. to talk about the earth) is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure, physical properties, dynamics, and history of Earth materials, and the processes by which they are formed, moved, and changed. The field is a major academic discipline, and is also important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards, some engineering fields, and understanding past climates and environments.

GEOLOGICAL EVOLUTION

The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations.

Rock units are first emplaced either by deposition onto the surface or intrude into the overlying rock. Deposition can occur when sediments settle onto the surface of the Earth and later lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows, blanket the surface. Igneous intrusions such as batholiths, laccoliths, dikes, and sills, push upwards into the overlying rock, and crystallize as they intrude.

After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed. Deformation typically occurs as a result of horizontal shortening, horizontal extension, or side-to-side (strike-slip) motion. These structural regimes broadly relate to convergent boundaries, divergent boundaries, and transform boundaries, respectively, between tectonic plates.

Atmosphere, climate, and weather

Blue light is scattered more than other wavelengths by the gases in the atmosphere, giving the Earth a blue halo when seen from space

The atmosphere of the Earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelops the Earth is held in place by the planet’s gravity. Dry air consists of 78% nitrogen, 21% oxygen, 1% argon and other inert gases, carbon dioxide, etc.; but air also contains a variable amount of water vapor. The atmospheric pressure declines steadily with altitude, and has a scale height of about 8 kilometres at the Earth’s surface: the height at which the atmospheric pressure has declined by a factor of e (a mathematical constant equal to 2.71…).[24][25] The ozone layer of the Earth’s atmosphere plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.

Terrestrial weather occurs almost exclusively in the lower part of the atmosphere, and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the polar regions much colder.

Weather can have both beneficial and harmful effects. Extremes in weather, such as tornadoes or hurricanes and cyclones, can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals dependent on its growth for their food.

A tornado in central Oklahoma.

A supercell thunderstorm.

The planetary climate is a measure of the long-term trends in the weather. Various factors are known to influence the climate, including ocean currents, surface albedo, greenhouse gases, variations in the solar luminosity, and changes to the planet’s orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including ice ages.

The climate of a region depends on a number of factors, especially latitude. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the tropical climate at the equator to the polar climate in the northern and southern extremes. Weather is also influenced by the seasons, which result from the Earth’s axis being tilted relative to its orbital plane. Thus, at any given time during the summer or winter, one part of the planet is more directly exposed to the rays of the sun. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the northern and southern hemispheres experience opposite seasons.

Weather is a chaotic system that is readily modified by small changes to the environment, so accurate weather forecasting is currently limited to only a few days. Overall, two things are currently happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes

Water on Earth

Panorama of the Iguazu waterfalls in Brazil.

Water is a chemical substance that is composed of hydrogen and oxygen and is vital for all known forms of life.[27] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth’s surface[28]. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[29] Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. Additionally, a minute amount of the Earth’s water is contained within biological bodies and manufactured products.

Oceans

A view of the Atlantic ocean from Leblon, Rio de Janeiro.
  • Arctic Ocean
  • Atlantic Ocean
  • Indian Ocean
  • Pacific Ocean
  • Southern Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth’s surface (an area of some 361 million square kilometers) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over 3,000 meters (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several ‘separate’ oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean or global ocean.[30][31] This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[32]

The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria: these divisions are (in descending order of size) the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean and the Arctic Ocean. The Pacific and Atlantic may be further subdivided by the equator into northerly and southerly portions. Smaller regions of the oceans are called seas, gulfs, bays and other names. There are also salt lakes, which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the Aral Sea and the Great Salt Lake.

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