"Pore Pressure through Earth Mechanical Systems" is a constitutive field theory that relates compactional strain to composition in the earth. Minerals and fluids are the dominant natural molecular matter in the earth. [Mass-energy] and [stress/strain] conservation are shown to be algebraically equivalent in a closed mathematical form in the earth. Relatively few measurements are needed to describe the earth's mechanical field. The physical basis for this theory is universal i.e. [force --balance] under [mass-energy] conserved boundary conditions. Earth mechanics theory satisfies Niels Bohr's "correspondence principle." It simultaneously explains both the accepted and the newer theories. The earth's "molecular mechanics" theory uses Newtonian mechanics as a limit as did Niels Bohr's when he revealed Quantum mechanics. The earth's elastic and plastic mechanical limits are connected to each other by their common (mineral-fluid) constituents. Earth mechanics depends directly to the laws of Newton, Coulomb, and Hooke. Earth mechanics theory is firmly rooted in fundamental mechanics between Newton's and Bohr's. Subsurface engineering involves a quantitative balance between human regulated forces in a well and those that are drilled into the earth. Pressures and stresses in the earth that were derived from empirical forced-fits were treated with a great deal of skepticism and given large engineering uncertainties. Earth Mechanical Systems present a new [closed-form] analytical design approach to drilling and subsurface engineering. Mechanical systems tend toward the minimum energy state. Each of these [force-balanced] equation systems is in a [closed-mathematical-form]. The earth is composed almost entirely of minerals and fluid. This [closed-form] synthesis relates physical laws to matter in the earth's sedimentary crust. Contact phil@Force-Balanced.net for general information or to order this book. Visit http: //www.Force-Balanced.net for more information on the earth's constitutive mechanical systems and their many applications. Copyright Phil Holbrook, 2003, all rights reserved. For book collectors; this book is an earth domain parallel to Newton's Principia. The energy of gravity acts in concert with electrostatic energy in the earth's sedimentary crust. The book's subtitle, "The force-balanced physics of the earth's sedimentary crust," describes the resulting scientific advancement. Autographed-by-author copies of this book can be had by contacting, phil@Force-Balanced.net. A great deal of information about the science can be seen at http: //www.Force-Balanced.net/textbook.htm.