This textbook deals with the most important items in Marine Geology, including some pioneer work. The list of topics has grown greatly in the last few decades beyond the items identified by Eugen Seibold as central and now includes prominently such things as methane and climate change; that is, the carbon cycle and the Earth system as a whole. Relevant geophysical, geochemical, sedimentological and paleontological methods are shortly described. They should allow the reader to comment on new results about plate tectonics, marine sedimentation from the coasts to the deep sea, climatological aspects, paleoceanology and the use of the sea floor. The text tries to transmit to the reader excitement of marine geological research both aboard and in modern laboratories. Basic mineralogical, geochemical, biological and other relevant data and a detailed list of books and symposia are given in an Appendix. This Introduction builds on the third edition of “The Sea Floor” byE. Seibold and W.H. Berger. While much of the original text was written by Seibold, a considerable portion of the material presented in this edition is new, taking into account the recent great shift in marine geological research, some of it with great relevance to human concerns arising in a rapidly changing world. Selected by Choice magazine as an Outstanding Academic Title for 2017 “The fourth edition incorporates a significant amount of new material, especially from geophysics and deep-ocean coring. … This edition includes a short glossary used primarily to define phrases or point to their occurrence in the text. … Summing Up: Highly recommended. Upper-division undergraduates and above; faculty and professionals.” (L. S. Zipp, Choice, Vol. 55 (4), December, 2017) This textbook deals with the most important items in Marine Geology, including some pioneer work. The list of topics has grown greatly in the last few decades beyond the items identified by Eugen Seibold as central and now includes prominently such things as methane and climate change; that is, the carbon cycle and the Earth system as a whole. Relevant geophysical, geochemical, sedimentological and paleontological methods are shortly described. They should allow the reader to comment on new results about plate tectonics, marine sedimentation from the coasts to the deep sea, climatological aspects, paleoceanology and the use of the sea floor. The text tries to transmit to the reader excitement of marine geological research both aboard and in modern laboratories. Basic mineralogical, geochemical, biological and other relevant data and a detailed list of books and symposia are given in an Appendix. This Introduction builds on the third edition of “The Sea Floor” by E.Seibold and W.H. Berger. While much of the original text was written by Seibold, a considerable portion of the material presented in this edition is new, taking into account the recent great shift in marine geological research, some of it with great relevance to human concerns arising in a rapidly changing world. Eugen Seibold was born in Stuttgart. He studied geology in Bonn and in Tϋbingen. Subsequently he taught at the University of Tübingen, but moved to Kiel in 1958 to study modern marine sedimentation and manage the Geological-Palaeontological  Institute of the University as its director. From 1980 he accepted positions as the President of the DFG (the German National Science Foundation), as Vice-President of the European Science Foundation, and as the President of the International Union of Geological Sciences. He was President of the European Science Foundation from 1984 to 1990, and a member of various academies, including the Leopoldina (Akademie der Naturforscher, Halle in Saxony-Anhalt) and the Académie des Sciences in Paris. Seibold’s many contributions to geology were well recognized – he was a recipient of internationally known awards (e.g., the Gustav-Steinmann Medal, the Hans-Stille Medal, the Leopold-von-Buch Plakette), as well as the Walter-KertzMedal in Geophysics and the Blue Planet Prize of the Asahi Foundation. The Asahi Foundation’s prize especially recognizes contributions of relevance to society. The prize was used, in part, to fund the Eugen and Ilse Seibold Prize, an award furthering Japanese-German scientific interaction. Among  outstanding paradigms within Seibold’s many contributions (including geologic education) one might emphasize his insights regarding the role of exchange between marginal basins and the open sea in determining the deposits accumulating in shelf basins. He assigned an estuarine-type exchange to black shale sedimentation and an anti-estuarine type to carbonate deposits.  Both types of sediment are prominent in the geologic record (and are conspicuous in the Jurassic of southern Germany, his original training ground). Significantly, black shales are commonly a source for hydrocarbon products, while carbonates often serve as reservoir rocks. Obviously, both rock types