Earth Structure and Plate Tectonic

The basic concept of the Earth structure and Plate Tectonic is good to know for drilling oil and gas wells.

The image below (Figure 1) shows the Earth structure. There are tree compositional layers which are curst, mantel and core. At the center of the Earth, the center core is a solid iron core which is surrounded by a liquid iron core. Core has a range between 2,900 – 6,370 km from surface. Mantel which has its range between 100 – 2,900 km consists of upper and lower mantel. Lower mantle (Meshosphere) is hot but strong due to high pressure however upper mantle is weak, hot and molten. Crust is a surface of the Earth and a majority of the Earth crust is made up of iron, silicon, oxygen and magnesium.

Figure 1 – Earth Structure

The lithosphere is the solid outer section of Earth, which includes Earth’s crust and the upper mantle.

Plate Tectonics

Plate Tectonics was initially introduced in 1960’s. The concept of the Plate Tectonics is the division of Earth into 12 plates and each plate moves as distinct units.

Figure 2 – Plate Tectonics

The plates floats on the partially molten asthenosphere and the plates can be moved (“Plate Movement”) due to convection currents within the asthenosphere. The direction of plate movement is shown in Figure 3.

Figure 3 – Plate Movement

The mechanism of plate movement is thought to be caused by convection currents in the asthenosphere. Hot magma which has less density slowly rises to surface and when it reaches the lithosphere, it becomes to cool down, therefore its density increases and it will sink. Rising of convection currents will move the Earth plate apart and this process is called “divergent”. On the other hand, sinking convection currents will move the Earth plate together which is called “convergent”.

Figure 4 – Convection Currents and Plate Movement Theories

The margins between the Earth plates are classified into 3 types which are Convergent, Divergent and Transform. The plates are constantly moving at very slow rate, therefore, the plates are regularly consumed and produced over time.

References 

Richard C. Selley, 2014. Elements of Petroleum Geology, Third Edition. 3 Edition. Academic Press.

Norman J. Hyne, 2012. Nontechnical Guide to Petroleum Geology, Exploration, Drilling & Production, 3rd Ed.. 3 Edition. PennWell Corp.

Richard C. Selley, 1997. Elements of Petroleum Geology, Second Edition. 2 Edition. Academic Press.

Anasofiapaixao, (2013), Earth-cutaway-schematic-english [ONLINE]. Available at: https://commons.wikimedia.org/wiki/File:Earth-cutaway-schematic-english.svg [Accessed 17 November 15].

Map of earth’s tectonic plates – type of boundary and direction “G115 – Introduction to Oceanography.” G115 – Introduction to Oceanography. The Trustees of Indiana University, n.d. Web. 10 Apr. 2015.  <http://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Ariel_Ellison/Ariel_Ellison/images1/earth_plates_lg.jpg>.

Surachit, (2007), Shows how ocean ridges are formed, lithosphere subducted at trenches; good for understanding plate tectonics. [ONLINE]. Available at: https://commons.wikimedia.org/wiki/File:Oceanic_spreading.svg [Accessed 17 November 15].

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