Arousing and sustaining young students' curiosity within school environments is an important concern in contemporary education. Our study investigated the triggers of curiosity in elementary classrooms centered around social constructivist discourse, specifically knowledge-building. To this end, we performed longitudinal network analysis on 4166 utterances over 28 lessons to extract directional relationships that best predicted expressions of curiosity in second and third grade students. For both grade levels, we found that a student's curiosity further stimulated curiosity of the same student or other students, indicating a social chain of curiosity. We further identified three types of teacher utterances--conveying information, giving positive responses, and reiterating students' opinions with uncertainty--as effective in stimulating student curiosity. The study expands our understanding of student curiosity in social constructivist classroom while offering preliminary insights into the broader question of how to design a classroom environment to promote the pursuit of knowledge.