Students commonly use gestures when describing geologic processes and features both in classroom and in field settings. Traditional gesture classification schemes lack the vocabulary to classify the diversity and complexity of gestures used by geologists. We have developed a new classification scheme that categorizes gestures by "type" (shape the hand makes) as well as by "function" (the gesture's purpose). We have defined five main "types" of gestures that are most commonly used by students when discussing geologic concepts: points, domains, flat-hands, frames and forms. We observe that each of these types may be used in a variety of ways to convey geological information and meaning. For example, a pointing gesture may be used to indicate direction, highlight or trace out a feature, or mimic a linear feature. To describe the purpose of the gestures, we have defined eight lower-order gesture "functions". These functions are fairly simplistic, indicating or describing a singular aspect about an object, feature, or process. Lower-order functions include: tracing, highlighting, locational, directional, constraining, rotational, sizing, and emphasis gestures. We have also defined three higher-order gesture functions. These functions often include more than one gesture type and/or more than one lower order function in combination or succession to describe or convey more detailed and/or complex concepts and processes. Higher-order functions include: sequential, illustrating, and constructing.

We have observed that while the types and functions used by geologists in field and non-field settings are the same, students in the field utilize lower-order gesture functions more frequently as they interact with their surroundings and perform initial observations. Students in non-field settings utilize more higher-order gesture functions as they must compose their ideas "from scratch". Students in the field may also utilize higher-order functions once they transition from observation into interpretation of their surroundings.