Fig. 1. Selected insights from the four themes identified with how geoscientists think and learn. (a) Like the heliocentric view of the solar system (left), the discovery of the brevity of human history within the vastness of geologic time (right) altered humanity’s understanding of its place in the cosmos. (b) In understanding the Earth as a system, feedback loops are a “threshold concept.” Even when the student understands a situation experientially (left), casting it into the symbolic language of flows, reservoirs, and feedbacks (right) remains exceptionally difficult. (c) Learning in the field offers many opportunities for students to experience making “first inscriptions.” Using senses and sensors, students transform the raw material of nature (left) into human artifacts: tractable, transportable symbols on paper (right). (d) Spatial thinking is common in geosciences and presents a stumbling block for students who have come up through an education system that did not develop, assess, or reward spatial skills. The illustrated exercise requires “visual penetrative ability,” which varies widely from student to student. Image credits are located in the supplement to this Eos issue (http://www.agu.org/eos_elec).