Text 7. Mineral deposits

 Mineral deposit is the concentrated, natural occurrence of one or more minerals. Mineral deposits can form within any kind of rock and consist of any type of mineral. They are valuable economically because they contain high concentrations of metallic and nonmetallic elements or other valuable materials that are essential to an industrial society.

The concentration of a mineral in a mineral deposit is important in determining whether it can be mined profitably. For the mining of metals, concentration in a mineral deposit is measured two ways. The grade depends on the percentage by weight of a metal in a mineral deposit. This percentage is measured by dividing the weight of the metal by the weight of the rock. The concentration factor (also called enrichment factor) is the number of times more abundant a metal is in a mineral deposit than it is in average crustal rock. The concentration factor is measured by dividing a mineral deposit’s grade by the average grade of crustal rocks for that metal. A concentration factor of ten, for example, means that a metal is ten times more abundant in a particular deposit than in the earth’s crust.

If a metal is to be mined profitably, it must have attained a minimum concentration factor - otherwise, the amount of that metal acquired will be too small to pay for the mining process. Minimum concentration factors vary from one metal to the next. Iron, which is relatively abundant in the earth’s crust, typically requires a concentration factor of between 5 and 10. Gold and silver, however, require concentration factors in excess of 2,000.

The accessibility of a mineral deposit also plays an important role in determining the cost-effectiveness of mining. In general, deposits that reside deeper in the crust are more difficult and more expensive to mine. Consequently, the minimum required concentration factor increases with the difficulty of extraction.

(1620)

Text 8. Geology

Geology is the study of the planet earth, its rocky exterior, its history, and the processes that act upon it. Geology is also referred to as earth science and geoscience. The word geology comes from the Greek geo, "earth," and logia, "the study of." Geologists seek to understand how the earth formed and evolved into what it is today, as well as what made the earth capable of supporting life. Geologists study the changes that the earth has undergone as its physical, chemical, and biological systems have interacted during its 4.5 billion year history.

Scientists use geology to understand how geological events and earth’s geological history affect people, for example, in terms of living with natural disasters and using the earth’s natural resources. As the human population grows, more and more people live in areas exposed to natural geologic hazards, such as floods, earthquakes, tsunamis, volcanoes, and landslides. Some geologists use their knowledge to try to understand these natural hazards and forecast potential geologic events, such as volcanic eruptions or earthquakes. They also study the geologic record of climate change in order to help predict future changes. As human population grows, geologists’ ability to locate fossil and mineral resources, such as oil, coal, iron, and aluminum, becomes more important. Finding and maintaining a clean water supply, and disposing safely of waste products, requires understanding the earth’s systems through which they cycle.

The field of geology includes subfields that examine all of the earth’s systems, from the deep interior core to the outer atmosphere, including the hydrosphere (the waters of the earth) and the biosphere (the living component of earth). Generally, these subfields are divided into the two major categories of physical and historical geology.

Many other scientific fields overlap extensively with geology, including oceanography, atmospheric sciences, physics, chemistry, botany, zoology, and microbiology. Geology is also used to study other planets and moons in our solar system. Specialized fields of extraterrestrial geology include lunar geology, the study of earth’s moon, and astrogeology, the study of other rocky bodies in the solar system and beyond. Scientific teams currently studying Mars and the moons of Jupiter include geologists.

(1990)

NOTES:

• core – керн, колонка породы, ядро;

• extraterrestrial geology - космическая геология;

• lunar geology - лунная геология.