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How the Earth Works

1. Discuss the age of the Earth, and tell how the discovery of radioactivity aided scientists in constructing a detailed geologic time recorded.

According to the evolutionary view on the age of the Earth, the planet is quite old. Most of the scientific literature on the subject indicates that the age of the Earth is approximately 4.5 to 5 billion years. These data are based on the radioactive dating of the samples of both earthly and meteoritic origin (The National Academy of Sciences). They have been obtained primarily by the lead-lead method developed by Clair Patterson. This figure corresponds to the age of the oldest terrestrial and lunar samples, and it has remained almost unchanged since 1956.

Radiometric dating is the method of determining the age of the Earth using radioactive isotopes. It is widely used in geology and other sciences. It is the source of all of the absolute dates of different events in the history of the Earth. Only the estimation of relative dates (bound to specific geological eras, periods, and epochs), the duration of which was unknown, was possible before the advent of radiometric dating.

2. Discuss the structure of the interior of the Earth, discussing its layers and the basics of plate tectonics.

The structure of the Earth consists of the crust, mantle, and core. he crust is a surface layer of the lithosphere. The density of this layer is lower than the density of other layers of the Earth. The upper part of the mantle, in its turn, is involved in many geological processes, such as volcanic eruptions and earthquakes, that have an effect on the crust. Therefore, it is assumed that the upper layer of the mantle and the crust form the lithosphere. Below the lithosphere there is the asthenosphere, which is less solid and more viscous, and its average temperature is 1200 °C. The asthenosphere is the source of volcanism. It contains pockets of molten magma, which is embedded in the Earth’s crust or poured on the Earth’s surface.

The mantle is the Earth’s geosphere, which surrounds the core and comprises 83% of the planet. Its lower boundary is located at the depth of 2900 km. The mantle is divided into a less dense and plastic upper part (800-900 km), which is formed from magma, and a crystalline bottom part (2000 km).

The core is situated in the center of the Earth. Its radius is approximately 3.500 km. The core temperature reaches 6000 °C. The core consists of iron and nickel alloys.

3. Describe the three ways in which rocks deform.

First, the deformation of rock mass occurs as a result of natural static (rock pressure). Second, deformmation may occur due to dynamic loads (tectonic movement, tectonic deformation of coal and gas, mining, and strokes.). Third, distortion may occur due to mechanical loading, blasting, and thermal (thermal expansion, phase transformation), electric, and magnetic influences during mining.

4. Discuss features of the seafloor, including volcanic islands and seamounts.

The seafloor is more diverse than the relief of the land surface. For example, its structure includes ridges, valleys, troughs, and cracks. Oceanic plateaus, ocean ridges, and continental slopes occupy a large portion of the bottom shelf.

The continental margin consists of the shelf (shallow), the continental slope, and the continental foot. The platform bordering continents, also referred to as the continental shelf, is rather uneven. On the outside of the shelf there are common rocky ledges; the average depth is approximately 130 meters (Nelson). The continental slope usually forms a clear and well-defined border with the shelf. In addition, it is almost always crossed by deep underwater canyons. As a rule, the boundary between the continental shelf and the slope is obvious. There are also seamounts, some of which are of volcanic origin. Another kind of submarine ridges is volcanic ridges. They consist of a chain of underwater volcanoes.

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