The Internet has revolutionized the way we learn. This edition expands upon integration of the Internet and textbook. We have added boxes that have a brief summary in the book, while the complete boxes are accessible through this book's web site. We have shortened some boxes from previous editions, but placed the full box on the web site. When we have found excellent and appropriate web sites, we have added URLs in the text and in figure captions. Our web site has enjoyable and enlightening web exercises that we have tested with our students, as well as animations of some of the figures from the textbook.

We have added new and revised artwork and photos. Some of the changes we have made for this edition include:

In chapter 1, we have added boxes on geology as a career and the origin of the solar system. We have added isostatic adjustment to the important concepts covered in the introductory chapter and have expanded the introduction to plate tectonics. In the minerals chapter, we have added a brief section on polarizing microscopy to the discussion of double refraction and referred the interested reader to a web site for more information. The introduction to the rock cycle has been moved to the beginning of the chapter on igneous rocks. In the chapter on igneous rocks and processes, we have overhauled our presentation of Bowen's reaction series to present what students need to know to understand igneous processes and use the web site for a more complete presentation of the reaction series. We give a thorough, illustrated explanation of how partial melting takes place in circulating asthenosphere above subducting crust. In the volcanoes chapter we have added a section on volcanoes and myths. We have also added a section that quantifies volcanic hazards. A new box looks at Mexico's Popocatepetl's recent eruptions and the potential for a disastrous eruption.

We have added a discussion of the twelve soil orders and updated the description and diagram of a soil profile to include the E Horizon. Abrasion has been removed as an agent of erosion. Chapter 6 has been expanded to include a discussion and diagram of the relation of plate tectonic settings and types of sedimentary rock. A new astrogeology box featuring the latest Mars Global Surveyor images discusses the importance of sedimentary rock to determining whether water and life once existed on Mars; the regression and transgression box has been moved to the web site and now includes animated diagrams.

In chapter 7, we have enhanced the description of the role of water in metamorphism to include why retrograde metamorphism is uncommon. We tie in the dehydration of metamorphic minerals during subduction to supplying the water necessary to partial melting of asthenosphere as described in the chapter on igneous rocks. In the chapter on geologic time, we have greatly expanded our coverage of isotopic dating to include descriptions of the mechanisms of radioactive decay. The recently dated, 4004 billion year old zircon crystal and its implications regarding early Earth history are discussed in that chapter.

Chapter 10 includes new photos of Niagara Falls and braided streams. The stream piracy section has been removed. The astrogeology box has been updated to include a discussion and latest photos of stream-like features on Mars from Nanedi Vallis canyon. Web site URLs provide easy access to additional images from the Mars Orbiter Camera. Chapter 11 includes a rewrite of the Darcy's Law box to address the influence of porosity on groundwater velocity though sediment or rock as well as revision of several diagrams showing the details of groundwater flow and fluctuation. The term speleothem has been added, and a discussion of thermophyllic bacteria around hot springs and the implication for early life is presented.

In the glaciers chapter, we have added a figure showing the extent of glaciation during the ice ages for the world (rather than just North America). We have pointed out that our present sea level is not permanent, because of episodes of more extensive glaciation and global warming.

Chapter 13 has improved maps of deserts and photos of desert features and more realistic diagrams of blowouts and migration of sand dunes; an image of barchan dunes from Mars Proctor Crater has also been added. In Chapter 14, the box on rising sea level has been updated and many diagrams have been redrawn to look more realistic while retaining clarity for the beginning geology student.

In the structure chapter, text and diagrams have been rewritten and redrawn to improve clarity of difficult concepts. An exciting addition to this new edition is the animated diagrams of folding and faulting to show the mechanics of movement and accommodation of strain in the crust.

Chapter 16 has undergone a major revision to include information and spectacular photos of the recent major earthquakes that have struck around the world - Seattle, India, El Salvador, Turkey, and Taiwan. New boxes on earthquake engineering and life-saving tips on what to do before, during, and after an earthquake have been added. The discussion of tsunamis has been revised and expanded to include new diagrams, photos, and a map of travel-time and early warning systems throughout the Pacific rim.

In the chapter on Earth's interior and its geophysical properties, we have updated and expanded our coverage of the core-mantle boundary to include a discussion of the D layer and ultra low velocity zone (ULVZ) as well as incorporating exciting new discoveries about the dynamics of the deep interior of Earth. Chapter 18 includes a new astrogeology box on the origin of the ocean. Maps of features on the sea floor have been revised.

In the chapter on mountains and the continental crust, we have expanded our coverage of the Appalachians by discussing their post-orogenic erosional and uplift history. Our geologic resources chapter now includes a box on frozen methane hydrates as a potential new energy resource along with its potential to contribute to global warming.