“The forms can change only if the energy applied to the system changes.”
From Hack, J.T., 1960, Interpretation of erosional topography in humid temperate regions: American Journal of Science, v. 258A, p. 80-97.
The study of geomorphology may have seen some of its most profound and fundamental research published during the mid-twentieth century. John T. Hack (1913-1991) was a foremost geologist who, while working for the USGS, studied the evolution of the Earth’s surface. In this 1960 publication, Hack came up with a time-independent model for erosion and landscape change. He noted that the Earth’s surface is an open system upon which many processes could act simultaneously. Hack was also the first to propose that uplift could be slow enough to counteract erosion, thus leading to landforms that could remain in steady-state until a major energy input occurred, such as through an orogeny or climate change. Hack’s theory sparked the study of the various processes controlling landscape evolution, and how these processes interact with one another on a multitude of scales.
Many geologists and geomorphologists have built upon Hack’s theory, and I am continuing this work to further understand the processes governing the evolution of the Rio Grande fluvial system in northern New Mexico.