Despite several phases of deformation, as a result of plate tectonics, parts of the continents still contain information on the initial cooling of the Earth. On the other hand, the ocean crust reflects the geodynamics of the Earth in the - geologically - short period of 150 Ma between its formation at mid-ocean ridges and assimilation in subduction zones. The study of oceanic ridges is the study of the driving forces of the geodynamic processes taking place within the Earth. The special feature of this book is its integration of the latest oceanograpic data with those of ophiolites - remnants of oceanic crust nowadays found on the continents. From this we gain a picture of molten submarine mountains that continuously create new ocean floor. This book is primarily written for students and scientists, but its comprehensible text - accompanied by numerous, mostly color, illustrations - is equally suitable for a broader readership.