Here is a list of online books about Earth Science in various formats available for free :

Acceptable Risk?: Making Decisions in a Toxic Environment

by Lee Clarke, 1991

Africa: Atlas of our Changing Environment

United Nations Environment Programme, 2008, 396 pages, 44MB, PDF

Antarctica: A Journey of Discovery

by Louise Huffman, Rita Thomas, Erin Carr, Katia Kontar, 2009, 60 pages, 113MB, PDF

Applications of Continuum Mechanics to Earth, Atmospheric, and Planetary Sciences

by Bradford Hager, 2006, PDF

Applied Geophysics

by Nicholas Rast, 1962

An Atlas of the Global Water Cycle

by Wee Ho Lim, Michael L. Roderick, 2009, 299 pages, 11MB, PDF

Atmospheric and Ocean Circulations

by Alan Plumb, 2003, 181 pages, 13MB, PDF

Atmospheric Pollution

by J.C. Jones, 2008, 109 pages, 4.1MB, PDF

Averting Catastrophe: Strategies for Regulating Risky Technologies

by J. Morone, E. Woodhouse, 1988

Basaltic Volcanism on the Terrestrial Planets

by members of the Basaltic Volcanism Study Project, 1981

Basic Earth Imaging

by Jon F. Claerbout Cecil, Ida Green, 2008, 236 pages, 4.3MB, PDF

Bathymetry and Its Applications

edited by Philippe Blondel, 2012, 148 pp, 30MB, PDF

California riparian systems: ecology, conservation, and productive management

by Richard E Warner, 1984

California’s salmon and steelhead: the struggle to restore an imperiled resource

by Alan Lufkin, 1990

Charles Lyell and Modern Geology

by Thomas George Bonney, 1895

CK-12 Earth Science

CK-12 Foundation, 2009

Climate and Transportation Solutions

by Daniel Sperling, James S. Cannon, 2010

The Carbon Neutral Myth: Offset Indulgences for Your Climate Sins

by Kevin Smith, 2007, 80 pages, 600KB, PDF

Carbon Trading: A Critical Conversation on Climate Change, Privatisation and Power

by L. Lohmann, N. Hallstrom, O. Nordberg, R. Osterbergh, 2006, 362 pages, 3.1MB, PDF

Clay Minerals in Nature: Their Characterization, Modification and Application

edited by M. Valaskova, G.S. Martynkova, 2012, 312 pp, 16MB, PDF

Climate Change

Wikibooks, 2012

Climate Change and Peak-Oil

by Kar Lee, 2012

Climate Variability: Some Aspects, Challenges and Prospects

edited by Abdel Hannachi, 2012, 192 pp, 12MB, PDF

Coal and the Environment

by S. F. Greb, C. F. Eble, D. C. Peters, A. R. Papp, 2006, 68 pages, 2.7MB, PDF

Concise Hydrology

by Dawei Han, 2010, 145 pages, 5MB, PDF

Data Analysis for Environmental Science and Management

by Bruce Kendall, Chris Costello, 2006, 136 pp, 800KB, PDF

Deserts: Geology and Resources

by A.S. Walker, 2000

The Discovery of Global Warming

by Spencer R. Weart, 2008, PDF

Dynamics of the Atmosphere

by Richard Lindzen, 2008, 312 pages, PDF

Earth and Environmental Sciences

edited by Imran Ahmad Dar, Mithas Ahmad Dar, 2011, 630 pp, 91MB, PDF

Earth Observation

edited by Rustam B. Rustamov, Saida E. Salahova, 2012, 254 pp, 15 MB, PDF

Earth Online: An Internet Guide for Earth Science

by Michael Ritter, 1997, PDF

Earth Soundings Analysis: Processing versus Inversion

by Jon F. Claerbout, 1992, 334 pages, 3.8MB, PDF

Earth Systems: an Earth Science Course

by Christine Loew, 2009, 154 pp, 400KB, PDF

Earthquakes, Volcanoes, and Tsunamis

National Science Teachers Association, 2007, 46 pp, 980KB, PDF

Earth’s Dynamic Systems

by W. Kenneth Hamblin, Eric H. Christiansen, 2003, 816 pp, online html

Earth’s Energy Imbalance and Implications

by J. Hansen, M. Sato, P. Kharecha, K. von Schuckmann, 2011, 52 pages, 1.1MB, PDF

The Elements of Geology

by William Harmon Norton, 1905

The Elements of Geology: Adapted to the Use of Schools and Colleges

by Justin R. Loomis, 1852, 198 pp, multiple formats

Elements of Physical Geography

by T.C. Hopkins, 1908, 516 pp, multiple formats

Encyclopedia Arctica

by Vilhjalmur Stefansson, 1951

by Joe Buchdahl, Sue Hare, 2000

Environmental Science in the Coastal Zone: Issues for Further Research

National Research Council, 1994, 184 pages

Environmental Technologies

by E. Burcu Ozkaraova Gungor, 2008, 268 pages, 3.5MB, PDF, Sciyo.com

Essentials of Geophysics

by Robert Van Der Hilst, 2004, PDF

Evolution of Physical Oceanography

edited by Bruce A. Warren and Carl Wunsch, 1980, 623 pages, PDF

Exercises in Active Tectonics

by Nicholas Pinter, 1996, 165 pages, PDF

Exploring the Deep Pacific

by Helen Raitt, 1956

The Forgiving Air: Understanding Environmental Change

by Richard C. J. Somerville, 1998

Fractal Analysis and Chaos in Geosciences

edited by Sid-Ali Ouadfeul, 2012, 174 pp, 9.4MB, PDF

Fundamentals of Air Pollution Engineering

by Richard C. Flagan, John H. Seinfeld, 1988, 554 pages, 19MB, PDF

Fundamentals of Geophysical Data Processing

by Jon Claerbout, 1985, 274 pages, PDF

Fundamentals of Physical Geography, 2nd Edition

by Michael Pidwirny, 2008

Gems and Gem Minerals

by Oliver C. Farrington, 1903

by John Wahr, 1996, 304 pages, 1.1MB, PDF

Geodetic Sciences: Observations, Modeling and Applications

by Shuanggen Jin, 2013, 344 pp, 19MB, PDF

Geodynamics

by Bradford Hager, 2006, PDF

Geology for Engineers

by Robert Fox Sorsbie, 1911

Global Climate Change And California: Potential Impacts And Responses

by Joseph B. Knox with Ann Foley Scheuring, 1992

Global Climate Change Impacts in the United States

by Thomas Karl, Jerry M. Melillo, and Thomas C. Peterson, 2009, 13MB, PDF

Global Warming Trigger Event

by Darryl Whitford, 2011, 76 pp, 5.6MB, PDF

Governing Climate: The Struggle For A Global Framework Beyond Kyoto

by Taishi Sugiyama, Editor, 2005, 142 pages, 1.1MB, PDF

by Christopher L. Liner, 1997, 131 pages, 450KB, PDF

Groundwater Hydrology

by Charles Harvey, 2005, PDF

Guidebook to the Geology of Barringer Meteorite Crater, Arizona

by David A. Kring, 2007, 154 pp, 136MB, PDF

Hard Truths: Facing the Hard Truths About Energy

by National Petroleum Council, 2007, 380 pages, 15MB, PDF

Image Estimation by Example: Geophysical Soundings Image Construction

by Jon Claerbout, Sergey Fomel, 2008, 330 pages, 9.5MB, PDF

Imaging the Earth’s Interior

by Jon F. Claerbout, 1985, 412 pages, PDF

Introduction to Crystallography and Mineral Crystal Systems

by Mike Howard, Darcy Howard, 1998

An Introduction to Fluid Motions, Sediment Transport, and Current-generated Sedimentary Structures by John Southard, 2006, 539 pages, PDF

Introduction to Mineralogy: A Collection of Copper Minerals

by Andrea Bangert, 2002

Introduction to Observational Physical Oceanography

by Raffaele Ferrari, Terrence Joyce, 2004, PDF

Introduction to Physical Oceanography

by Robert H. Stewart, 2008, 353 pages, 10MB, PDF

by J.A. Scales, M.L. Smith, S. Treitel, 2001, 208 pp, 1.7MB, PDF

Manual of the Chemical Analysis of Rocks

by Henry Stephens Washington, 1904

Mathematical Geography

by Willis E. Johnson, 1907, 346 pages, 5.8MB, PDF

Metal Mining and the Environment

by T. L. Hudson, F. D. Fox, G. S. Plumlee, 1999, 68 pages, 1.4MB, PDF

Meteorology

by J. G. M’Pherson, 1905

Meteorology: Theoretical And Applied

by H. Wendell, R. Longley, 1944

Mineralogy

by F. H. Hatch, 1912, PDF/TXT/DJVU

Minerals and Rocks

by J. Richard Wilson, 2010, 163 pages, 9.8MB, PDF

Natural Aerosols in the Climate System

by Charlie Zender, 2011, 254 pp, 2.4MB, PDF

The Nature of Northern Australia

by J. Woinarski, B. Mackey, H. Nix, B. Traill, 2007, 136 pages, 16MB, PDF

New Achievements in Geoscience

edited by Hwee-San Lim, 2012, 212 pp, 29MB, PDF

New Theory of the Earth, 2nd Edition

by Don L. Anderson, 2007, 405 pages, 13MB, PDF

Observatory Seismology

edited by J. J. Litehiser, 1990

Oceanographic and Geophysical Tomography

by Y. Desaubies, A. Tarantola, J. Zinn-Justin, 1990, 463 pages, PDF

The Oceans, Their Physics, Chemistry, and General Biology

by H. U. Sverdrup, M. W. Johnson, R. H. Fleming, 1942

One Earth, One Future: Our Changing Global Environment

by Cheryl Simon Silver with Ruth S. DeFries, 1990

Origin and Evolution of Earth: Research Questions for a Changing Planet

Committee on Grand Research Questions in the Solid-Earth Sciences, 2008

Our Ocean Planet: Oceanography in the 21st Century

by Robert Stewart, 2008

An Outline of American Geography

by Stephen S. Birdsall, John Florin, 1992

Paleoceanography

by Edward Boyle, 2008, PDF

A Photographic Atlas of Rock Breakdown Features in Geomorphic Environments

by Mary Bourke and Heather Viles, 2007, 15MB, PDF

The planet we live on: The beginnings of the Earth Sciences

by Chris King, 2010, 196 pp, 16MB, PDF

Plate Tectonics

by Kare Kullerud, 2003

A Practical Guide to Geostatistical Mapping

by Tomislav Hengl, 2009, 291 pages, 19MB, PDF

The Practical Oceanographer: A Guide to Working At-Sea

by Rick Chapman, 2004, 159 pages, 1.5MB, PDF

Radiative Transfer in the Earth System

by Charlie Zender, 2010, 178 pp, 2.8MB, PDF

Recent Hurricane Research: Climate, Dynamics, and Societal Impacts

edited by Anthony Lupo, 2011, 616 pages, 58MB, PDF

Regional Oceanography: an Introduction

by Matthias Tomczak, 2002, 402 pages, PDF

The Remote Sensing Tutorial

by Nicholas M. Short, 2009, NASA

Rogue Waters

by A. Slunyaev, I. Didenkulova, E. Pelinovsky, 2011, 51 pp, 4.9MB, PDF

Scripps Institution of Oceanography: Probing the Oceans 1936 to 1976

by Elizabeth Noble Shor, 1978

Sediment Transport

edited by Silvia Susana Ginsberg, 2011, 334 pages, 31MB, PDF

Sedimentary Geology

by John Southard, 2007, PDF

Statistical Physics of Fracture, Friction and Earthquake

by Hikaru Kawamura, et al. 2011, 52 pp, 2MB, PDF

Statistics and Physical Oceanography

National Academies Press, 1993

Sustainable Energy – Without the Hot Air

by David JC MacKay, 2009, 383 pages, 9.7MB, PDF

Tectonics

edited by Damien Closson, 2011, 358 pages, 96MB, PDF

Tectonics: Recent Advances

edited by Evgenii Sharkov, 2012, 330 pp, 52MB, PDF

by Marian Ivan, 2008, 80 pages, PDF

by John Scales, 1997, 297 pages, 5.7MB, PDF

Theory of the Earth

by Don L. Anderson, 1989, 382 pages, 30MB, PDF

This Dynamic Earth: The Story of Plate Tectonics

by W. Jacquelyne Kious, Jacqueline W. Kious, Robert I. Tilling, 2001, 77 pages, 3.7MB, PDF

Trace-Element Geochemistry

by Frederick Frey, 2009, PDF

Traces of Catastrophe

by Bevan M French, 1998, 120 pp, 20MB, PDF

Trouble in the Air: Global Warming and the Privatised Atmosphere

by Patrick Bond and Rehana Dada, 2005, 242 pages, 1.7MB, PDF

The Tsunami Threat: Research and Technology

edited by Nils-Axel Moerner, 2011, 714 pages, 173MB, PDF

Turbulence in the Ocean and Atmosphere

by Raffaele Ferrari, Glenn Flierl, 2007, PDF

by Jack Dangermond, Matt Artz, 2012, 35 pp, 6MB, PDF

Unsaturated Zone Hydrology for Scientists and Engineers

by James Tindall, James Kunkel, 1998, 624 pages, PDF

Volcanology and Geothermal Energy

by Kenneth Wohletz, Grant Heiken, 1992

Water Encyclopedia: Science and Issues

Advameg, Inc. 2009

Wave Motion in the Ocean and the Atmosphere

by Paola Rizzoli, 2008, PDF

Weather Explained

Advameg, Inc. 2009

Weather Science: An Elementary Introduction to Meteorology

by F.W. Henkel, 1911, 368 pp, multiple formats

A Wet Look at Climate Change: Hurricanes to House Mites

by Peter Moir, 2012, 91 pp, 6.9MB, PDF

Why, and How, Should Geologists Use Compositional Data Analysis

by Ricardo A. Valls, 2008, 58 pp, 3.7MB, PDF

Why could ice ages be unpredictable?

by Michel Crucifix, 2013, 42 pp, 1.8MB, PDF