The Whole Earth

This chapter illustrates how elements and compounds are separated from the hydrosphere and crust of Earth, and put to use. The hydrosphere, which includes saltwater and freshwater above and below Earth s surface, must supply the water necessary to sustain hfe. The soluble salts in the oceans are a commercial source of magnesium, bromine, and sodium chloride, which is not only table salt but also an essential chemical raw material. 

FIGURE 18.1 A cross-section of Earth. Geologists customarily list the composition of Earth in terms of oxides, as shown here. 

Hydrosphere All freshwater and saltwater that is part of planet Earth Minerals Naturally occurring, solid inorganic compounds 

Silicates Quartz SiOg Glass, ceramics, alloys 

Oxides Hematite FCgOg Iron ore, paint pigment 

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Water and carbon play critical roles in many of the Earth s chemical and physical cycles and yet their origin on the Earth is somewhat mysterious. Carbon and water could easily form solid compounds in the outer regions of the solar nebula, and accordingly the outer planets and many of their satellites contain abundant water and carbon. The type I carbonaceous chondrites, meteorites that presumably formed in the asteroid belt between the terrestrial and outer planets, contain up to 5% (m/m) carbon and up to 20% (m/m) water of hydration. Comets may contain up to 50% water ice and 25% carbon. The terrestrial planets are comparatively depleted in carbon and water by orders of magnitude. The concentration of water for the whole Earth is less that 0.1 wt% and carbon is less than 500 ppm. Actually, it is remarkable that the Earth contains any of these compounds at all. As an example of how depleted in carbon and water the Earth could have been, consider the moon, where indigenous carbon and water are undetectable. Looking at Fig. 2-4 it can be seen that no water- or carbon-bearing solids should have condensed by equilibrium processes at the temperatures and pressures that probably were typical in the zone of fhe solar... 

Tilt variations also do not affect the annual total of solar energy received by the whole Earth, but do change the annual total for polar regions (simultaneously for both hemispheres). Tilt also affects the seasonal insolation at high latitudes, with greater tilt leading to warmer summers and cooler winters in both hemispheres. 

Successes of this type indicate that important prebiotic syntheses may have occurred either in regions on the primordial Earth where temperatures were low, or in a period where temperatures on the whole Earth were low (Cleaves et al., 2006). 

This section will end by clearing up an important point of nomenclature. By a system , we mean the part of our universe which we are dealing with. This can be the whole Earth, the solar system, or one tiny little cell. We distinguish between three types of systems ... 

Fig. 1.4. Estimated composition of the whole Earth, showing the mass fraction of each element on a logarithmic scale. (Reproduced with permission from P.A. Cox (1989), see Further Reading.)...

The day was calm and the sky blue. An extraordinary peace and depthless serenity seemed to touch everything. It was as if the whole earth was softly exhaling its exhilaration. Had such a mood... 

Above him were seraphs, each with six wings With two wings they covered their faces, with two they covered their feet, and with two they were flying. And they were calling to one another Holy, holy, holy is the LORD Almighty the whole earth is full of his glory. At the sound of their voices the doorposts and thresholds shook and the temple was filled with smoke. 

From glucose alone various organisms synthesize a whole series of polymeric glucans with quite different properties. Of these, cellulose, an unbranched (1-1,4-linked polyglucose (Fig. 4-5A), is probably the most abundant. It is the primary structural polysaccharide of the cell walls of most green plants.65 For the whole Earth, plants produce 1014 kg of cellulose per year. 

Capt. I have already told you how I wandered over the whole earth. In the course of my journeying I came to Taprobane, and was compelled to go ashore at a place, where through fear of the inhabitants I remained in a wood. When I stepped out of this I found myself on a large plain immediately under the equator. 

On the interior wall of the first circuit all the mathematical figures are conspicuously painted — figures more in number than Archimedes or Euclid discovered, marked symmetrically, and with the explanation of them neatly written and contained each in a little verse. There are definitions and propositions, etc. On the exterior convex wall is first an immense drawing of the whole earth, given at one view. Following upon this, there are tablets setting forth for every separate country the customs both public and private, the laws, the origins and the power of the inhabitants and the alphabets the different people use can be seen above that of the City of the Sun. 

How, then, is this done Our Sage answers "With our Pontic and Catholic Water, which in its refulgent course irrigates and fertilizes the whole earth (of the Sages), and is sweet, beautiful, clear, limpid, and brighter than gold, silver, carbuncles, and diamonds."... 

Figure 7.15 Noble gas elemental abundance (log10 >) relative to the solar abundance in planetesimals of various sizes are plotted against a mass number. The amount of noble gases is normalized to Si. In the case of atmospheric values (thick line), M, stands for the noble gases in the atmosphere and Si, in the whole Earth.

It was during the same time that astronomers began to extract quantitative information about elemental abundances in the Sun by solar absorption spectroscopy and it was soon realized that the compositions of the Sun and the whole Earth are similar, except for hydrogen and other extremely volatile elements (see Russell, 1941). 

Table 1 Composition of the mantle of the Earth assuming average solar system element ratios for the whole Earth.

The four elements—magnesium, silicon, iron, and oxygen—contribute more than 90% by mass to the bulk Earth. As stated above, magnesium, silicon, and iron have approximately similar relative abundances (in atoms) in the Sun, in chondritic meteorites, and probably also in the whole Earth. On a finer scale there are, however, small but distinct differences in the relative abundances of these elements in chondritic meteorites. Figure 10 shows the various groups of chondritic meteorites in an Mg/Si versus Al/Si plot. As discussed before, the Earth s mantle has Al/Si and Al/Mg ratios within the range of... 

The crust is the Earth s major repository of incompatible elements and thus factors prominently into geochemical mass-balance calculations for the whole Earth. For this reason, and to understand the processes by which it formed, determining the composition of the continental crust has been a popular pursuit of geochemists from the time the first rocks were analyzed. 

The last element of the group of metalloids is astatine. It has been estimated that the whole Earth s crust contains less than 44 mg astatine and this element with the atomic number 85 can thus be considered one of the rarest naturally occurring elements on Earth. All isotopes of this radioactive element have short half-lives and are products of several radioactive decay series. At (ti/2 = 54 s) occurs in one rare side branch of the decay series while At, one of the products of a side branch of the Po decay series, undergoes a very fast P decay (ti/2 = IxlO s). 

Despite the abundant evidence for huge plume events, such as the immense Bushveld event, the anthropic principle implies that the whole Earth has not experienced 2>100°C greenhouse conditions as long as life has existed. Since then, there have always been parts of the Earth below about 100°C, and since the evolution of mesophiles there have been parts of the Earth below about 40°C. Possibly the plume events have simply been too small to disrupt global climate beyond habitability. Or possibly life itself has played a hand. 

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