The main mass of the Earth's water shell is formed by the salty waters of the World Ocean, covering 2/3 of the Earth's surface. Their volume is approximately 1379106 km3, while the volume of all land waters (including glaciers and groundwater to a depth of 5 km) is less than 90106 km3. Since oceanic waters make up about 93% of all waters in the biosphere, it can be assumed that their chemical composition determines the main features of the composition of the hydrosphere as a whole.

The modern chemical composition of the ocean is the result of its long-term change under the influence of the activities of living organisms. The formation of the primary ocean was due to the same processes of degassing of the solid matter of the planet that led to the formation gas envelope Earth. For this reason, the composition of the atmosphere and the hydrosphere is closely related, their evolution was also interconnected.

As noted earlier, water vapor and carbon dioxide dominated among the degassing products. From the moment the surface temperature of the planet dropped below 100 ° C, water vapor began to condense and form primary reservoirs. On the surface of the Earth, the process of the water cycle arose, which marked the beginning of the cyclic migration of chemical elements in the land-ocean-land system.

In accordance with the composition of the released gases, the first accumulations of water on the planet's surface were acidic, enriched mainly in HC1, as well as HF, H3BO3, and H2S. Ocean water has gone through many cycles. Acid rains vigorously destroyed aluminosilicates, extracting easily soluble cations from them - sodium, potassium, calcium, magnesium, which accumulated in the ocean. Cations gradually neutralized strong acids, and the waters of the ancient hydrosphere acquired a chlorine-calcium composition.

Among the various processes of transformation of degassable compounds, apparently, the activity of condensations of thermolithotrophic bacteria took place. The appearance of cyanobacteria that lived in water, protecting them from harmful ultraviolet radiation, marked the beginning of photosynthesis and biogeochemical oxygen production. The decrease in the partial pressure of CO2 due to photosynthesis contributed to the precipitation of large masses of carbonates Fe2+, then Mg2+ and Ca3+.

Free oxygen began to flow into the waters of the ancient ocean. Over a long period of time, reduced and underoxidized compounds of sulfur, ferrous iron and manganese were oxidized. The composition of oceanic water acquired a chloride-sulfate composition close to the modern one.

Chemical elements in the hydrosphere are in various forms. Among them, the most characteristic are simple and complex ions, as well as molecules that are in a state of highly dilute solutions. There are widespread ions that are sorption bound with particles of colloidal and subcolloidal sizes present in sea water in the form of a fine suspension. A special group is made up of elements of organic compounds.

The total amount of dissolved compounds in sea water (salinity) in the surface layers of the oceans and marginal seas ranges from 3.2 to 4%. In inland seas, salinity varies over a wider range. The average salinity of the World Ocean is assumed to be 35%.

Even in the middle of the XIX century. scientists have discovered a remarkable geochemical feature of ocean water: despite fluctuations in salinity, the ratio of the main ions remains constant. The salt composition of the ocean is a kind of geochemical constant.

As a result of the persistent work of scientists from many countries, extensive analytical material has been accumulated that characterizes the content of not only the main, but also trace chemical elements in the water of the seas and oceans. The most substantiated data on the average values ​​(clarks) of chemical elements in the water of the World Ocean are given in the reports of E.D. Goldberg (1963), A.P. Vinogradov (1967), B. Mason (1971), G. Horn (1972), A.P. Lisitsina (1983), K.N. Turekiana (1969). In table. 4.1 mainly uses the results of the last two authors.

As can be seen from the above data, the bulk of the dissolved compounds are chlorides of common alkaline and alkaline earth elements, sulfates are less, and even less are hydrocarbonates. The concentration of trace elements, the unit of which is µg/l, is three mathematical orders of magnitude lower than in rocks. The range of clarks of scattered elements reaches 10 mathematical orders, i.e. approximately the same as in the earth's crust, but the ratios of the elements are completely different. Bromine, strontium, boron and fluorine clearly dominate, the concentration of which is above 1000 µg/l. Iodine and barium are present in significant amounts, their concentration exceeds 10 µg/l.

Table 4.1

Part of the metals in the water - molybdenum, zinc, uranium, titanium, copper - has a concentration of 1 to 10 µg/l. The concentration of nickel, manganese, cobalt, chromium, mercury, cadmium is much lower - hundredths and tenths of µg/l. At the same time, iron and aluminum, which play the role of the main elements in the earth's crust, have a lower concentration in the ocean than molybdenum and zinc. The least dissolved elements in the ocean are niobium, scandium, beryllium and thorium.

To determine some geochemical and biogeochemical indicators, it is necessary to know the concentration of elements not only in sea water, but also in the solid phase of soluble substances, i.e. in the amount of salts in sea water. The table shows the data, for the calculation of which the value of the average salinity is assumed to be 35 g/l.

As shown above, the leading factor in the evolution of the chemical composition of the ocean over the course of geological history was the total biogeochemical activity of living organisms. Organisms play an important role in modern processes differentiation of chemical elements in the ocean and the removal of their masses in the sediment. According to the biofiltration hypothesis developed by A.P. Lisitsin, planktonic (mainly zooplankton) organisms daily filter through their bodies about 1.2107 km3 of water, or about 1% of the volume of the World Ocean. At the same time, thin mineral suspensions (particles with a size of 1 micron or less) bind into lumps (pellets). Pellets sizes from tens of micrometers to 1 - 4 mm. The binding of fine suspensions into lumps ensures a faster settling of the suspended material on the Bottom. At the same time, part of the chemical elements dissolved in water in the bodies of organisms passes into insoluble compounds. The most common examples of the biogeochemical binding of dissolved elements into insoluble compounds are the formation of calcareous (calcite) and silicic (opal) skeletons of planktonic organisms, as well as the extraction of calcium carbonate by calcareous algae and corals.

Among pelagic silts (deep-sea sediments of the ocean), two groups can be distinguished. The former consist mainly of biogenic plankton formations, the latter are formed mainly by particles of non-biogenic origin. In the first group, calcareous (carbonate) silts are most common, in the second - clayey silts. Carbonate silts occupy about a third of the area of ​​the bottom of the World Ocean, clayey - more than a quarter. In carbonate sediments, the concentration of not only calcium and magnesium, but also strontium and iodine increases. Silts, where clay components predominate, contain much more metals. Some elements are very weakly removed from solution into silts and gradually accumulate in sea water. They should be called talas-sophilic. Calculating the ratio between the concentrations in the sum of soluble salts of sea water and silts, we will obtain the value of the thalassophylicity coefficient of CT, which shows how many times this element is more in the salt part of ocean water compared to sediment. Thalassophilic elements accumulating in the dissolved salt part of water have the following CT coefficients:

Knowing the mass of an element in the World Ocean and the value of its annual income, it is possible to determine the rate of its removal from the oceanic solution. For example, the amount of arsenic in the ocean is approximately 3.6109 t, with river runoff brought 74103 t/year. Consequently, for a period equal to 49 thousand years, there is a complete removal of the entire mass of arsenic from the oceans.
The assessment of the time spent by elements in a dissolved state in the ocean was undertaken by many authors: T.F. Bart (1961), E.D. Goldberg (1965), H.J. Bowen (1966), A.P. Vinogradov (1967) and others. The data of different authors have greater or lesser discrepancies. According to our calculations, the periods of complete removal of dissolved chemical elements from the World Ocean are characterized by the following time intervals (in years, in the sequence of increasing periods in each series):

• n*102: Th, Zr, Al, Y, Sc
• n*103: Pb, Sn, Mn, Fe, Co, Cu, Ni, Cr, Ti, Zn
• n*104: Ag, Cd, Si, Ba, As, Hg, N
• n*105: Mo, U, I
• n*106: Ca, F, Sr, B, K
• n*107: S, Na
• n*108: C1, Br

For all the tentativeness of such calculations, the orders of magnitude obtained make it possible to distinguish groups of trace elements that differ in the duration of their stay in the oceanic solution. Elements that are most intensely concentrated in deep-sea silts have the shortest residence time in the ocean. These are thorium, zirconium, yttrium, scandium, aluminum. The periods of presence of lead, manganese, iron, and cobalt in the oceanic solution are close to them. Most of the metals are completely removed from the ocean over several thousand or tens of thousands of years. Thalassophilic elements have been in a dissolved state for hundreds of thousands of years or more.

Significant masses of dispersed elements in the ocean are bound by dispersed organic matter. Its main source is dying planktonic organisms. The process of destruction of their remains is most active up to a depth of 500-1000 m. Therefore, in the sediments of shelf and shallow continental seas, huge masses of dispersed organic matter of marine organisms accumulate, to which organic suspensions are added, taken out by river runoff from land.

The main part of the organic matter of the ocean is in a dissolved state and only 3 - 5% is in the form of suspension (Vinogradov A.P., 1967). The concentration of these suspensions in the water is low, but their total mass in the entire volume of the ocean is very significant: 120 - 200 billion tons. The annual accumulation of highly dispersed organic detritus in the sediments of the World Ocean, according to V.A. Uspensky, exceeds 0.5109 tons.

Dispersed organic matter sorbs and entrains a certain complex of dispersed elements into sediments. With a certain convention, their content can be judged by the microelement composition of large accumulations of organic matter - deposits of coal and oil. The concentration of elements in these objects is usually given in relation to the ash; Equally important are data relative to the original, unashed material.

As can be seen from Table. 4.2, the microelement composition of coal and oil is fundamentally different.

Table 4.2

Average concentrations of trace metals in coal and oil, 10-4%

Oil has a different ratio, a significantly higher concentration of many trace elements. The high content of titanium, manganese and zirconium in hard coals is due to mineral impurities. Among the scattered metals, the highest concentration is typical for zinc, chromium, vanadium, copper and lead.

Organic matter actively accumulates many toxic elements (arsenic, mercury, lead, etc.), which are constantly removed from ocean water. Consequently, dispersed organic matter, like mineral suspensions, plays the role of a global sorbent that regulates the content of trace elements and protects the environment of the World Ocean from dangerous levels of their concentration. The amount of trace elements bound in dispersed organic matter is very significant, given that the mass of matter in sedimentary rocks is hundreds of times greater than the total amount of all deposits of coal, coal shale and oil. According to J. Hunt (1972), N.B. Vassoevich (1973), A.B. Ronova (1976) the total amount of organic matter in sedimentary rocks is (1520)1015 tons.

The masses of scattered elements accumulated in the organic matter of the Earth's sedimentary stratum are measured in many billions of tons.

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The only source of practical importance that controls the light and heat regime of water bodies is the sun.

If the sun's rays falling on the surface of the water are partly reflected, partly spent on the evaporation of water and illuminating the layer where they penetrate, and partly absorbed, then it is obvious that the heating of the surface layer of water occurs only due to the absorbed part of the solar energy.

It is no less obvious that the laws of heat distribution on the surface of the World Ocean are the same as the laws of heat distribution on the surface of continents. Particular differences are explained by the high heat capacity of water and the greater homogeneity of water compared to land.

In the northern hemisphere, the oceans are warmer than in the southern, because in the southern hemisphere there is less land, which greatly heats the atmosphere, and there is also wide access to the cold Antarctic region; in the northern hemisphere there is more land, and the polar seas are more or less isolated. The thermal equator of water is located in the northern hemisphere. Temperatures naturally decrease from the equator to the poles.

The average surface temperature of the entire World Ocean is 17°.4, i.e., it is 3° higher than the average air temperature by the globe. The high heat capacity of water and turbulent mixing explain the presence of large reserves of heat in the oceans. For fresh water, it is equal to I, for sea water (with a salinity of 35‰) it is slightly less, namely 0.932. On average annual output, the warmest ocean is the Pacific (19°.1), followed by the Indian (17°) and the Atlantic (16°.9).

Temperature fluctuations on the surface of the World Ocean are immeasurably smaller than air temperature fluctuations over the continents. The lowest reliable temperature observed on the surface of the ocean is -2°, the highest is +36°. Thus, the absolute amplitude is not more than 38°. As for the amplitudes of average temperatures, they are even narrower. The daily amplitudes do not go beyond 1°, and the annual amplitudes, which characterize the difference between the average temperatures of the coldest and warmest months, range from 1 to 15°. In the northern hemisphere for the sea, the warmest month is August, the coldest is February; vice versa in the southern hemisphere.

According to thermal conditions in the surface layers of the World Ocean, tropical waters, waters of the polar regions and waters of temperate regions are distinguished.

Tropical waters are located on both sides of the equator. Here in the upper layers the temperature never drops below 15-17°, and in large areas the water has a temperature of 20-25° and even 28°. Annual temperature fluctuations do not exceed 2° on average.

The waters of the polar regions (in the northern hemisphere they are called arctic, in the southern hemisphere antarctic) are distinguished by low temperatures, usually below 4-5 °. The annual amplitudes here are also small, as in the tropics - only 2-3°.

The waters of the temperate regions occupy an intermediate position - both territorially and in some of their features. Part of them, located in the northern hemisphere, was called the boreal region, in the southern - the notal region. In boreal waters, the annual amplitudes reach 10°, and in the notal region, they are half as much.

The transfer of heat from the surface and the depths of the ocean is practically carried out only by convection, i.e., by the vertical movement of water, which is caused by the fact that the upper layers turned out to be denser than the lower ones.

The vertical temperature distribution has its own characteristics for the polar regions and for the hot and temperate regions of the World Ocean. These features can be summarized in the form of a graph. The upper line represents the vertical temperature distribution at 3°S. sh. and 31°W d. in Atlantic Ocean, i.e., serves as an example of a vertical distribution in tropical seas. What is striking is the slow decrease in temperature in the very surface layer, the sharp drop in temperature from a depth of 50 m to a depth of 800 m, and then again a very slow drop from a depth of 800 m and below: the temperature here almost does not change, and, moreover, it is very low (less than 4 °C). ). This constancy of temperature at great depths is explained by the complete rest of the water.

The lower line represents the vertical temperature distribution at 84°N. sh. and 80 ° in. etc., i.e. serves as an example of a vertical distribution in the polar seas. It is characterized by the presence of a warm layer at a depth of 200 to 800 m, overlapped and underlain by cold water with negative temperatures. Warm layers, found in both the Arctic and Antarctic, were formed as a result of the submergence of water brought to the polar countries. warm currents, because these waters, due to their higher salinity compared to the desalinated surface layers of the polar seas, turned out to be denser and, therefore, heavier than the local polar waters.

In short, in temperate and tropical latitudes there is a steady decrease in temperature with depth, only the rates of this decrease are different at different intervals: the smallest near the surface itself and deeper than 800-1000 m, the largest in the interval between these layers. For the polar seas, that is, for the Arctic Ocean and the southern polar space of the other three oceans, the pattern is different: the upper layer has low temperatures; with depth, these temperatures, rising, form a warm layer with positive temperatures, and under this layer, temperatures again decrease, with their transition to negative values.

This is the picture of vertical temperature changes in the oceans. As for individual seas, the vertical temperature distribution in them often deviates greatly from the patterns that we have just established for the World Ocean.

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hydrosphere (water shell of the Earth), which occupies the vast majority of it (more than $90\%$) and is a combination of water bodies(oceans, seas, bays, straits, etc.) washing land areas (continents, peninsulas, islands, etc.).

The area of ​​the World Ocean is about $70\%$ of the planet Earth, which exceeds the area of ​​the entire land by more than $2$ times.

The World Ocean, as the main part of the hydrosphere, is a special component - the oceanosphere, which is the object of study of the science of oceanology. Thanks to this scientific discipline, the component, as well as the physicochemical composition of the oceans are now known. Let us consider in more detail the component composition of the World Ocean.

The World Ocean can be componentally divided into its main components, independent large parts that communicate with each other - the oceans. In Russia, on the basis of the established classification, four separate oceans were distinguished from the composition of the World Ocean: the Pacific, Atlantic, Indian and Arctic. In some foreign countries, in addition to these four oceans, there is also a fifth one - the South (or the South Arctic), which combines the waters of the southern parts of the Pacific, Atlantic and Indian oceans surrounding Antarctica. However, due to the uncertainty of the boundaries, this ocean is not distinguished in the Russian classification of oceans.

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Seas

In turn, the component composition of the oceans includes seas, bays, straits.

Definition 2

Sea- this is a part of the ocean, limited by the shores of the continents, islands and bottom elevations and differing from neighboring objects in physico-chemical, environmental and other conditions, as well as characteristic hydrological features.

According to morphological and hydrological features, the seas are divided into marginal, mediterranean and interisland.

The marginal seas are located on the underwater margins of the continents, the shelf zone, in transition zones and are separated from the ocean by islands, archipelagos, peninsulas or underwater rapids.

The seas that are confined to continental shallows are shallow. For example, the Yellow Sea has maximum depth equal to $106$ meters, and those seas that are located in the so-called transition zones are characterized by depths of up to $4 \ 000$ meters - Okhotsk, Bering and so on.

The water of the marginal seas practically does not differ in physical and chemical composition from the open waters of the oceans, because these seas have an extensive connection front with the oceans.

Definition 3

mediterranean called seas that cut deep into the land and are connected to the waters of the oceans by one or more small straits. This feature of the Mediterranean seas explains the difficulty of their water exchange with the waters of the oceans, which forms a special hydrological regime of these seas. The Mediterranean seas include the Mediterranean, Black, Azov, Red and other seas. The Mediterranean seas, in turn, are divided into intercontinental and intracontinental.

Interisland seas are separated from the oceans by islands or archipelagos, consisting of rings of individual islands or island arcs. Such seas include the Philippine Sea, the Fiji Sea, the Banda Sea, and others. The Sargasso Sea also belongs to the inter-island seas, which does not have definitely established and pronounced boundaries, but has a pronounced and specific hydrological regime and special types of marine flora and fauna.

Gulfs and straits

Definition 4

gulf- this is a part of the ocean or sea, protruding into the land, but not separated from it by an underwater threshold.

Depending on the nature of origin, hydrogeological features, forms of the coastline, shape, as well as confinement to a particular region or country, bays are divided into: fjords, bays, lagoons, estuaries, bays, estuaries, harbors and others. The Gulf of Guinea, washing the coast of the countries of Central and West Africa, is recognized as the largest in area.

In turn, the oceans, seas and bays are interconnected by relatively narrow parts of the ocean or sea, which separate the continents or islands - straits. The straits have their own special hydrological regime, a special system of currents. The widest and deepest strait is the Drake Strait, which separates South America and Antarctica. Its average width is 986 kilometers and a depth of more than 3,000 meters.

Physical and chemical composition of the waters of the World Ocean

Sea water is a highly dilute solution of mineral salts, various gases and organic matter, containing in its composition suspensions of both organic and inorganic origin.

A series of physico-chemical, ecological and biological processes constantly occur in sea water, which have a direct impact on the change general composition solution concentration. The composition and concentration of mineral and organic substances in ocean water are actively influenced by tributaries fresh water flowing into the oceans, evaporation of water from the surface of the ocean, precipitation on the surface of the World Ocean, the processes of formation and melting of ice.

Remark 1

Some processes, such as the activity of marine organisms, the formation and decay of bottom sediments, are aimed at changing the content and concentration of solids in water and, as a result, at changing the ratio between them. The respiration of living organisms, the process of photosynthesis and the activity of bacteria affect the change in the concentration of dissolved gases in water. Despite this, all these processes do not violate the concentration of the salt composition of water in relation to the main elements included in the solution.

Salts and other minerals and minerals dissolved in water organic matter are predominantly in the form of ions. The composition of salts is diverse, almost all chemical elements are found in ocean water, but the main mass is made up of the following ions:

• $Na^+$
• $SO_4$
• $Mg_2^+$
• $Ca_2^+$
• $HCO_3,\CO$
• $H2_BO_3$

The highest concentrations in sea waters contain chlorine - $1.9\%$, sodium - $1.06\%$, magnesium - $0.13\%$, sulfur - $0.088\%$, calcium - $0.040\%$, potassium - $0.038\%$, bromine $0.0065\%$, carbon $0.003\%$. The content of other elements is insignificant and amounts to about $0.05\%.$

The total mass of matter dissolved in the World Ocean is more than $50,000$ tons.

Precious metals were found in the waters and at the bottom of the World Ocean, but their concentration is insignificant and, accordingly, their extraction is unprofitable. Ocean water in its chemical composition is strikingly different from the composition of land waters.

The salt concentration and salt composition in different parts of the World Ocean is not uniform, however, the greatest differences in salinity are observed in the surface layers of the ocean, which is explained by exposure to various external factors.

The main factor that makes adjustments to the concentration of salts in the waters of the World Ocean is atmospheric precipitation and evaporation from the water surface. The lowest salinity values ​​on the surface of the World Ocean are observed at high latitudes, since these regions have an excess of precipitation over evaporation, significant river runoff and melting of floating ice. As you approach the tropical zone, salinity increases. In the equatorial latitudes, the amount of precipitation increases, and the salinity here again decreases. The vertical distribution of salinity is different in different latitudinal zones, but deeper than $1500$ meters, salinity remains almost constant and does not depend on latitude.

Remark 2

Also, in addition to salinity, one of the main physical properties sea ​​water is its transparency. The transparency of water is understood as the depth at which the white disc of Secchi with a diameter of $30$ centimeters ceases to be visible to the naked eye. The transparency of water depends, as a rule, on the content of suspended particles of various origins in the water.

The color or color of water also largely depends on the concentration of suspended particles, dissolved gases, and other impurities in the water. The color can vary from blue, turquoise and blue hues in clear tropical waters to blue-green and greenish and yellowish hues in coastal waters.

The hydrosphere is the shell of the Earth, which is formed by oceans, seas, surface water bodies, snow, ice, rivers, temporary water flows, water vapor, clouds. The shell, composed of reservoirs and rivers, oceans has a discontinuous character. The underground hydrosphere is formed by underground currents, groundwater, artesian basins.

The hydrosphere has a volume equal to 1,533,000,000 cubic kilometers. Water covers three fourths of the Earth's surface. Seventy-one percent of the Earth's surface is covered by seas and oceans.

The huge water area largely determines the water and thermal regimes on the planet, since water has a high heat capacity, it has a large energy potential. Water plays an important role in the formation of the soil, the appearance of the landscape. The waters of the oceans are different chemical composition water is almost never found in distilled form.

Oceans and seas

The world ocean is a body of water that washes the continents, it makes up more than 96 percent of the total volume of the earth's hydrosphere. Two layers of the water mass of the world's oceans have different temperatures, which ultimately determines the temperature regime of the Earth. The world's oceans accumulate the energy of the sun, and when cooled, part of the heat is transferred to the atmosphere. That is, the thermoregulation of the Earth is largely due to the nature of the hydrosphere. The world ocean includes four oceans: Indian, Pacific, Arctic, Atlantic. Some scientists single out the Southern Ocean, which surrounds Antarctica.

The world ocean is distinguished by the heterogeneity of water masses, which, located in a certain place, acquire distinctive characteristics. The bottom, intermediate, surface and subsurface layers are distinguished vertically in the ocean. The bottom mass has the largest volume, it is also the coldest.

Sea - part of the ocean that extends into the mainland or adjacent to it. The sea differs in its features from the rest of the ocean. The basins of the seas develop their own hydrological regime.

The seas are divided into internal (for example, the Black, Baltic), inter-island (in the Indo-Malay archipelago) and marginal (seas of the Arctic). Among the seas, inland (White Sea), intercontinental (Mediterranean) are distinguished.

Rivers, lakes and swamps

An important component of the Earth's hydrosphere is rivers, they contain 0.0002 percent of all water reserves, 0.005 percent of fresh water. Rivers are an important natural reservoir of water, which is used for drinking, industry, and agriculture. Rivers are a source of irrigation, water supply, watering. Rivers are fed by snow cover, groundwater and rainwater.

Lakes occur when there is excess moisture and in the presence of basins. Basins can be of tectonic, glacial-tectonic, volcanic, cirque origin. Thermokarst lakes are common in permafrost regions, floodplain lakes are often found in river floodplains. The regime of lakes is determined by whether the river carries water out of the lake or not. Lakes can be endorheic, flowing, represent a common lake-river system with a river.

Swamps are common on the plains in conditions of waterlogging. The lowlands are fed by soils, the upland ones are fed by precipitation, the transitional ones are fed by soils and precipitation.

The groundwater

Groundwater is located at different depths in the form of aquifers in rocks. earth's crust. Groundwater lies closer to the surface of the earth, groundwater is located in deeper layers. Of greatest interest are mineral and thermal waters.

Clouds and water vapor

Water vapor condensate forms clouds. If the cloud has a mixed composition, that is, it includes ice and water crystals, then they become a source of precipitation.

Glaciers

All components of the hydrosphere have their own special role in the global processes of energy exchange, global moisture circulation, and affect many life-forming processes on Earth.