We evaluate a 4-year (2018–2022) museum-based geoscience outreach program hosted by the Santa Cruz Museum of Natural History and featuring geoscience PhD students. From 2018-2022, the program consisted of monthly pop-up events focused on rock identification and fundamental rock types. From 2020–2022, the program transitioned to a series of live videos, streamed via the Museum's website and social media, that focused on specific geoscience topics. The duration of this program and its overlap with shifting modes of audience contact during the COVID-19 pandemic provide an opportunity to evaluate long-term trends in attendance and quality of engagement through both in-person and virtual media.

In-person pop-ups typically attracted 10-20 visitors per 2-hour event, including visitors in attendance specifically for rock identification. Unfortunately, attendance data was not routinely collected until 2019. However, the physical pop-up interactions were characterized by extended conversations that lasted at least several minutes.

Virtual pop-ups were streamed weekly for four months, then shifted to monthly. Mean viewership for both weekly and monthly pop-ups was approximately 310 views per event, although this overestimates engagement as "views" are counted after only three seconds of viewing. We hosted 35 virtual pop-ups with a shallow negative trend in attendance over the two-year duration, with distinct peaks (up to 800 views) for specific topics, including climate change and local focus.

Virtual events were characterized by an order of magnitude higher audience engagement. Although different attendance metrics complicate intercomparison, learning outcome comparisons are more straightforward. In-person events led to fewer, but higher quality interactions, while online events reached a larger audience. In-person engagement was participatory and interactive, typically lasting 3-10 minutes, whereas virtual engagement was passive and of poorly defined duration. We speculate that this lesser "quality control" of virtual outreach may have contributed to waning audience interest.