Communities of resistance are increasingly turning to radical tactics, including acts of civil disobedience, to fight back against encroaching fossil fuel infrastructure. The fight against the Mountain Valley Pipeline (MVP) is no exception. The MVP is a 303-mile long proposed fracked gas pipeline in Virginia and West Virginia. I apply radical flank effect (RFE) theory and the theory of movement dynamism to understand the role of civil disobedience, as a radical flank, in the MVP resistance movement. I contribute to the literature on RFEs by focusing primarily on how the radical flank of this movement has affected within-movement social dynamics, like trust, unity, and interpersonal relations. I rely on 15 semi-structured interviews with pipeline fighters, both those who have and have not participated in acts of civil disobedience, to gain insight into the use of civil disobedience, as a radical flank in the movement. This movement has used diverse tactics to challenge construction of the MVP, making it a strong case for understanding the role of radical tactics, and their relationship to moderate tactics. I find several positive RFEs (energizing effects, connecting effects, engaging effects, uniting effects, and movement outcome effects) and some potential negative RFEs (conflict/alienation, fear of consequences and organizational risks). I also find evidence of movement dynamism in the form of an ecosystem of tactics which emerged in the MVP resistance movement. Movement actors kept moderate and radical flanks publicly separate for strategic reasons while overlapping membership bridged the social dynamics of the movement, encouraging cohesion and collective movement identity. / Master of Science / Communities concerned about climate change are increasingly breaking the law in order to make their voices heard and stop dangerous coal, oil and natural gas projects. These actions are called civil disobedience and they have been used for decades in the United States, most prominently in the Civil Rights Movement. One such example in the fight against climate change is the resistance to the Mountain Valley Pipeline, a 303-mile long proposed natural gas pipeline in Virginia and West Virginia. I use social movement theories to understand the role that civil disobedience has played in the Mountain Valley Pipeline resistance movement. Specifically, I look at how the use of civil disobedience in this movement has affected the social dynamics of the movement, like trust, unity, or relationships in the movement. I spoke with 15 community members who have been active in fighting this pipeline to learn more. This movement has involved a wide range of different tactics, including civil disobedience, so it is a strong example to study for this research. My interviews with the community members revealed several positive effects as a result of the use of civil disobedience in the movement as well as a few potential risks/dangers. I also found that civil disobedience was able to work together with other types of tactics in a vibrant ecosystem that included mutual benefit. At the same time, I find that community members sought to keep some of the illegal tactics separate from more moderate tactics, like lawsuits or public comment submissions, in order to keep the moderate tactics safe. Despite this separation, I find that significant overlap of community members across different types of tactics was able to maintain a cohesive, common identity and unify people who were participating in different tactics, but fighting the same pipeline.