国际工程资料Basic Geology (1).pdfVIP

PgDip/MSc The Energy Programme/Subsurface Basic Geology Basic Geology Review In this topic the student is introduced to the fundamentals of the Earth’s structure, plate tectonics and rock types. Content Earth Structure Figure 1 illustrates the structure of the Earth. There is a central solid iron core, surrounded by a liquid iron core, the lower mantle and the upper mantle. The upper mantle consists of a weak, partially molten asthenosphere and a strong lithosphere with a surficial crust of light rock. About 90% of the earth’s crust is made up of the four elements: iron, oxygen, silicon and magnesium, which are the fundamental building blocks of most minerals. Iron, being heavy, sinks to the core, and lighter elements such as silicon, aluminium, calcium, potassium and sodium have risen to the crust. Figure 1. The Earth’s Structure. (From THE DYNAMIC EARTH by B.J. Skinner and S.C. Porter, copyright © 2000 John Wiley and Sons. This material is used by permission of John Wiley and Sons, Inc.) © The Robert Gordon University 2006 1 PgDip/MSc The Energy Programme/Subsurface Basic Geology Plate Tectonics Plate Tectonics was first proposed in the 1960’s. The central idea is the division of the lithosphere into 12 rigid plates (6 major ones), which each move as distinct units (Figure 2). The plates consist of rigid lithosphere (with either thin, dense oceanic crust or thick, less dense continental crust), which ‘floats’ on the partially molten asthenosphere (Figure 3). Convection currents within the asthenosphere are thought to be the driving force behind the plate movement. Where hot matter rises under the ocean it flows apart and carries the plates along with it (Figure 4). When this hot matter cools and sinks the plates also begin to sink. The plates are constantly m