Abstract: As part of a science education reform initiative, a series of Web GIS tectonics investigations with educative materials and embedded supports were developed. These supports were designed to address the need to provide “just in time” professional development to help educate teachers about important tectonics concepts and to support their development of geospatial pedagogical content knowledge to teach with a novel Web-based curriculum. A curriculum implementation study was conducted with twelve grade 8 urban middle level science teachers that implemented the Web GIS investigations with 1,124 students. Data sources included a student pretest-posttest tectonics measure, 33 classroom observations, a post-implementation survey and a focus group interview. Results indicated that the educative curriculum materials were effective in supporting the science teachers’ professional growth during the curriculum enactment and supported their teaching of the Web GIS investigations.