Relative vertical displacements and average relative vertical velocities have been determined for bench marks located throughout Yellowstone National Park (YNP) by comparing geodetic leveling measurements made in 1923 (second order), 1936 (third order), 1941 (third order), 1955 (third order), 1960 (first order), and 1975–1977 (first order). The 1923–1975 data indicate uplift greater than 400 mm (7.7 mm/yr) of an area approximately 15–20 km wide and at least 40 km long which is centered along the northeast trending axis of the 600,000‐year‐old Yellowstone caldera; the maximum 1923–1975 vertical displacement in this area is 726 mm (14.0 mm/yr). The existence of a well‐defined and untilted Yellowstone Lake terrace implies that the 1923–1975 average vertical velocities cannot have been maintained for more than a few hundred years. The 1955–1977 data from central YNP indicate that the northeastern caldera half has risen relative to the southwestern half at an average velocity of about 8 mm/yr; a similar bias is present in the 1923–1975 data but it is less pronounced. The 1923–1960 and 1960–1975 data from northwestern YNP, and a 200 mm depression in the 1923–1975 data near Norris Junction, may be interpreted in terms of deformation associated with the 1959 Hebgen Lake earthquake and the 1975 Yellowstone Park earthquake. A composite profile of the 1936–1977 and 1941–1977 average vertical velocity data which skirts the edge of the Yellowstone caldera in northeastern YNP is most easily explained as the result of random leveling error and/or bench mark instabilities. The apparent youth of the 1923–1975 Yellowstone uplift and its close association with the Yellowstone caldera suggest that the most likely cause of the uplift is a recent (not more than 500 years ago) influx of molten material into the upper crust beneath the caldera.

Comparison of precise leveling measurements made in 1923 with those made in 1975, 1976, and 1977 reveals that the 600,000-year-old Yellowstone caldera is being uplifted relative to its surroundings. Maximum relative uplift since 1923 is in excess of 700 millimeters-about 14 millimeters vertically per year. The most likely cause of this rapid and unusually large surface deformation is a recent influx of molten or partially molten materials to a location within the crust beneath Yellowstone National Park.

A compilation of aeromagnetic and new earthquake data is used to characterize the current tectonic activity and crustal properties of the Yellowstone hot spot. Earthquakes located during detailed surveys from 1972 to 1976 occurred west and northeast of the Yellowstone caldera along east‐west zones and south of the caldera in north‐south zones. The change in trend suggests that Yellowstone is at a vertex of the contemporary tectonic patterns. Seismicity showed variations of maximum focal depths from ∼20 km outside the Yellowstone caldera to ∼5 km inside the caldera. The frequency of earthquake occurrence was markedly lower within the caldera. Fault plane solutions showed general north‐south extension west of the caldera, a suggestion of radial compression near the western caldera rim, and northeast to southeast extension south of the caldera. Spectral analyses of aeromagnetic data indicate the Curie isotherm to be 10±3 km below sea level at the periphery of the caldera. These data support the hypothesis of a magma source within the crust for the Yellowstone hydrothermal activity, but they do not bear on the definition of a deep mantle source for the Yellowstone hot spot.

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High‐resolution reflection seismic and detailed gravity data were acquired across an exposure of the Wasatch fault, Utah, near a trench excavated for dating of Quaternary fault displacement. The seismic data across the Quaternary Wasatch fault are interpreted to show three subparallel surfaces dipping from 70°W at the surface to an estimated 45°W at 40 m, displaced unconsolidated sediments, and colluvial material abutting the main fault. Detailed gravity data were of assistance in mapping the sediment‐bedrock interface from the rangefront across the Wasatch Fault Zone. A combined high‐resolution seismic and gravity interpretation reveals that bedrock is 80 m deeper in the hanging wall than in the footwall, suggesting that displacement has occurred on several en echelon blocks in the near‐surface of the Wasatch fault. Movement on the most recent Wasatch fault trace began prior to deposition of Pleistocene lacustrine sediments. The twelvefold, high‐resolution reflection seismic data were recorded and processed to achieve vertical resolution of approximately 1 m and horizontal resolution (Fresnel zone radii) of as good as 5 m on the deepest reflecting interfaces at 40 m. Reasonably high frequencies and good bandwidth (about 80–300 Hz) in the stacked seismic data permitted a direct comparison to the trenched cross section. Good correlation between the trench stratigraphy and structure and the seismic data suggests high‐resolution seismic data can be a valuable tool for analyzing near‐surface faulting in unconsolidated sediment and for locating potential trench sites.