China
Africa
Explore chapters and articles related to this topic
Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
A plate tectonic is a massive irregular-shaped block of solid earth lithosphere comprising land and ocean earth crust. It is also called a lithospheric plate. A tectonic plate is of various sizes, from a few hundred to thousands of kilometers across. The earth’s crust is made up of eight major and eight to ten minor tectonic plates. Tectonic describes the motion and movements of these plates, and it is related to the underground geological forces that bring about changes in the earth’s crust. The plate tectonics theory explains how the plates move across the earth’s surface and how the crust is being destroyed and created. The word tectonics means a ‘builder’. The place where two plates meet is known as a plate boundary.
Our Earth, its minerals and ore bodies
Published in Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith, The Business of Mining, 2019
Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith
The fundamental basis for the theory of plate tectonics is the recognition that the outer layers of the Earth are made up of seven major and numerous minor moving plates (Figure 1.5). Each plate comprises a crustal component and the upper part of the upper mantle, known as the lithospheric mantle. This combination forms a rigid outer zone called the lithosphere and hence the lithospheric plates. The thickness of the lithosphere in areas dominated by oceanic crust is approximately 100 km compared to 200 km in areas dominated by continental crust. The layer of the upper mantle beneath the lithospheric mantle is known as the asthenosphere, which is weaker (plastic) and denser compared to the lithosphere. Hence the lithospheric plates essentially float on top of the asthenosphere and these changes enable the plates to move independently from the asthenosphere.
The geological origin of building stones
Published in John A. Hudson†, John W. Cosgrove, Understanding Building Stones and Stone Buildings, 2019
John A. Hudson†, John W. Cosgrove
A weak layer in the mantle, the asthenosphere shown in Figure 2.5, allows the mantle and crust above it (known collectively as the lithosphere) to become detached from the underlying mantle. Plate tectonics, the process that dominates the deformation of the Earth’s crust, is the result of the horizontal movement of various sections of the lithosphere, known as the tectonic plates (see Fig. 2.6), with respect to each other. When the plates move apart, they form oceans characterised by a major, central fracture zone within which large quantities of basaltic magma rise to produce mid-oceanic ridges. These are the divergent plate boundaries shown on Figure 2.6. When plates move towards one another (the subduction zones shown in Fig. 2.6), the resulting collision produces mountain belts and large quantities of granitic magma. Ancient mountain belts can be recognised by these associated belts of granites, and, as discussed later in this chapter, two such belts occur within Britain and these have provided building stones for some of our most prestigious buildings. The plate margins (Fig. 2.6) are regions of the Earth where major faulting occurs and are therefore major zones of seismicity and earthquakes.
Convection in an internally cooled fluid layer heated from below
Published in Geophysical & Astrophysical Fluid Dynamics, 2018
Convection layers cooled or heated from within and heated or cooled at one boundary, while the other boundary is insulating, have received increasing attention in recent years. Many geophysical and astrophysical convection systems can be described in this way in first approximation. The Earth’s atmosphere is an example in that heating by solar radiation occurs at the ground, while heat is radiated into space in a more homogeneous way in the upper regions. See, for example, the discussion of Berlengiero et al. (2006). Plate tectonics is believed to be a manifestation of convection in the Earth’s mantle which is driven mainly by heat sources generated by the decay of radioactive elements. A similar situation occurs in the meltdown of a nuclear reactor and there are numerous other engineering examples where convection is driven by nearly homogeneous heating, while cooling occurs at a boundary.