Townsend, MeredithColón Umpierre, Ana2022-02-182022-02-182022-02-18https://hdl.handle.net/1794/27063Hogg Rock is a basaltic-andesite dome located in the Central Oregon Cascades. Its flat top, steep sides, and glacial striations and lakes have led to the interpretation that Hogg Rock was a dome that erupted subglacially. It is also highly fractured, a characteristic often found in ice-magma deposits. We mapped the fractures at Hogg Rock and found three different types of fractures: cube joints, plate joints (also known as entablature), and pseudo- columnar joints. We also mapped the orientations of the fractures where possible. We found that the fractures were mainly horizontal and radially oriented around the butte, suggesting that Hogg Rock cooled from the outside in, and further supporting the interpretation that Hogg Rock erupted subglacially. We also measured the fracture density of the joints, and found that the platey joints represented the finest scale of jointing.en-USAll Rights Reserved.cooling fracturesglaciovolcanismsantiam passvolcanismElectronic Thesis or Dissertation