[1][2][3][4][5][6] Ewing has been described as a pioneering geophysicist who worked on the research of seismic reflection and refraction in ocean basins, ocean bottom photography, submarine sound transmission (including the SOFAR channel), deep sea core samples of the ocean bottom, theory and observation of earthquake surface waves, fluidity of the Earth's core, generation and propagation of microseisms, submarine explosion seismology, marine gravity surveys, bathymetry and sedimentation, natural radioactivity of ocean waters and sediments, study of abyssal plains and submarine canyons.

[7] Ewing worked as an instructor at the Rice Institute while pursuing his PhD before joining the faculty at Lehigh University in 1930, where he served until 1944.

Dr. Ewing (often simply called 'Doc' by those who worked with him) was the founder (established in 1949) and first director of Lamont Geological Observatory (now known as Lamont–Doherty Earth Observatory (LDEO) in Palisades, New York) where he worked with J. Lamar Worzel (gravity specialist), Dr. Frank Press (seismologist), Jack Nafe, Jack Oliver, and geologists and oceanographic cartographers Dr. Bruce Heezen and Marie Tharp.

In 1972 he joined the University of Texas Medical Branch at Galveston, and was named the head of the Division of Earth and Planetary Sciences of the Marine Biomedical Institute.

He originated Project Mogul, an early program to detect Soviet nuclear weapons tests.