**4. Discussion and Conclusions**

Because the solid earth tide has two equally strong peaks each day at the H2G site whereas the H2 venting peaks only one, it appears unlikely that solid earth tides play a dominant role in producing the observed daily changes in H2 venting in the Sao Francisco Basin of Brazil. It is possible that the solid earth tide contributes to the venting, but the atmospheric pressure tide must be (and could be) the dominant control. Biologic control on venting is, to our knowledge, the only other potential control. It awaits evaluation.

**Author Contributions:** Conceptualization, J.S., P.F., L.C., methodology, J.S., A.P.; writing-original draft, L.C.; writing-review and editing, all. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
