Reference

G.J. MacDonald, a prominent figure in the field of geophysics, raised several significant questions about deep continental structures. His work, as referenced in the search results, particularly in the paper titled "Major Questions About Deep Continental Structures" available on Semantic Scholar, suggests that he was deeply involved in understanding the composition and dynamics of the Earth's crust. MacDonald's inquiries likely revolved around the formation, evolution, and current state of the continental crust, including its thickness, composition, and the processes that shape it. His work aimed to address how these structures influence geological activities such as earthquakes and the formation of mineral deposits. Unfortunately, without access to the full text of MacDonald's paper, specific questions he posed cannot be detailed here. However, his contributions to the field are well-documented and continue to influence current research. For more detailed insights into MacDonald's major questions, one could refer to his publications or scholarly articles that discuss his work in depth. Semantic Scholar provides a starting point for further exploration of MacDonald's contributions to understanding deep continental structures.