By John Grover and J. Barry Maynard

Stimulated in part by his undergraduate experience at Antioch College and persuaded by what he believes to be important and right, Len Larsen has devoted his professional career to becoming and being a master teacher. He has always undertaken research projects that would bear directly on and inform his capabilities as a teacher. His decision to work in the Beartooth and Crazy Mountains, for example, stemmed from a conviction that he could not adequately teach metamorphic and igneous petrology unless he was personally familiar with the problems and occurrences that were to be encountered in the field. Len has been ever eager to gain experience - probably for a geologist the most important attribute - and to impart that experience in turn to his students, giving them an appreciation of real rocks in conjunction with learning in the classroom. Furthermore, convinced that experimental and theoretical methods are important in petrology, Len spent a sabbatical leave at Penn State learning how to carry out hydrothermal experiments and getting a practical and intuitive feeling for phase equilibrium determinations. His goal was to give depth and understanding to his lectures on phase diagrams, and his research on zircon solubilities - carried out in hydrothermal apparatus he subsequently set up at the University of Cincinnati - was a natural professional outgrowth of this desire to give our students the best possible grounding in petrology.

In the classroom, Len has always worked to give geologists a skill, and perhaps more importantly, a skill coupled with the knowledge and confidence that they really know what they are doing. Len has produced more than a generation's worth of good petrographers - an important and unusual record for a geology department in this age of theoretical knowledge with little practical skill. Time and again our graduates tell us that they could begin projects in petrology knowing what they knew and knowing it well. Whether in graduate school or industry, our graduates report that their skill and confidence in petrography put them far ahead of their fellows from other backgrounds. It will be very hard, in Len's absence, for us to maintain that substantial advantage in the quality of our majors' program, but he has shown us how important it is and we will most assuredly try.

In the field Len is without equal in bringing a group of colleagues or students to see and to understand. Although he may be somewhat shy in social circumstances, Len is Socrates on an outcrop, helping each person to imagine a process in light of what he sees. Little escapes Len's eyes, but rather than lecture, he works to help others see, and seeing, to create a scenario in time and space that will explain what is present. Two extremely important principles govern Len's teaching in the field, principles that every geologist should recall but often will not: the first is that it is essential to think in three dimensions. Although it might seem that three-dimensional visualization should be intuitive for all who live in a three-dimensional world, our experience as teachers of geology is that most people have to learn how to project the images of the printed page or TV screen, with which we are so familiar, into the third dimension. We must teach our students how to imagine geologic structures might be oriented as they plunge away from sight into the earth. Len Larsen can do so with ease and skill, and he knows how to help us flatlanders expand our horizons in search of reality and truth underground.

The second principal governing Len's teaching in the field is that "everyone is equal on the outcrop." He believes that the skill to see and the disciplined imagination required to explain what one sees cannot be developed fully in the classroom. Although reading and Iectures certainly inform, our real understanding of rocks can only b accomplished as we explore the realities of Nature in all its variations and exceptions. And until we see the rocks, no amount of training can give us the knowledge or competence to explain how they form. Len recognizes that the depths of understanding that come from seeing are related most to the quality of looking, not to facts recalled. Thus, anyone capable of looking well and seeing clearly - whatever his professional status - can discover the truth. The delightful corollary to this idea - and a characteristic of field work that has attracted people to the geological sciences for two centuries - is that on the outcrop we are all students and colleagues. No academic hierarchy can survive in an environment where simple, accurate observation can tumble uninformed theory or professional pomposity. Len Larsen has taught us that teachers of geology are most successful who willingly break down the divisions that separate faculty from students, and accept the friendship and collegiality of anyone who shares an interest in the Earth. This same spirit gives our discipline a special character, and nourishes that relaxed informality, warm camaraderie, mutual respect and shared enthusiasm that accompany our excursions. Most of us find it hard to transport that spirit back to the classroom; Len Larsen succeeds here in a way we could emulate, for his students love and respect him, and he them. Perhaps more than facts imparted or even insights gained on the outcrop, that reciprocal affection between Len and his student colleagues shows us that he is, indeed, a master teacher.