The course for which this book is used is an introductory geology course comprising both physical geology and historical geology. It is offered usually as a one-semester course but sometimes a full-year course. This course is found in geology or earth science departments at 2- and 4-year schools. Students are usually freshmen or sophomores fulfilling a core science requirement. There are usually no prerequisites. The one-term course often goes by the name Introduction to Geology, or Introductory Geology, but sometimes, the course could be disguised under some misleading title, such as Earth Science. In the two-semester sequence, the first semester covers physical geology and is sometimes a prerequisite for the second course (historical); in some cases too, the physical geology portion extends partway into the second semester. Course names are more direct - Physical Geology for one term and Historical Geology for the other term. While the combined, or Introduction to Geology, course has had fluctuations in course size, both the Physical Geology and Historical Geology course areas have grown in market size over the years.