It is in these mountains that the described rock was found (‘Washington Geologic Newsletter’ 56)
According to further research, there is evidence suggesting that uplifting of the Cascade Mountains that occurred in the Columbian river, which is denoted as the ancestral Columbia river exhibited a coincidence that saw the formation of a canyon through cutting. In the years that followed, fluid deposition and intracanyon flows accounted for the existence of basalt in the river channel. Such basalt is the basic material that formed the volcanic rocks similar to the type presented in the image.
The latest event in the Columbia River basalt was the deposition of the saddle mountain basalt. Saddle Mountains have been described as containing high silica content, and of noticeably thin nature compared to other basalts of the Columbian river (70). The nature of appearance is the result if extensive compression as well as that of the ensuing extensional events that followed as the deposited basalt