Ursula Marvin

"Mainstream geology is founded upon enunciated by James Hutton (1726–1797) and Charles Lyell (1797–1875), who argued that, during unlimited expanses of time, the Earth has undergone slow, ceaseless change by processes we can observe in operation. In their view, we cannot call on any powers that are not natural to the globe, admit of any action of which we do not know the principle, nor allege extraordinary events to explain a common appearance. A , originating from outside the Earth, and wreaking change instantaneously. Such a process violates every tenet of uniformitarianism. Largely for this reason, hypotheses of impact origin for craters on the Earth and the moon were vigorously opposed for the better part of the past century. Space-age research now has established beyond doubt the authenticity of impact as a geologic process, but an abundance of evidence exists that a wide chasm still persists between the views of impact specialists and those of terrestrial geologists. A full realization of the ramifications of impact processes may have been delayed by the advent of , which engulfed the geological community in the late 1960s. Revolutionary as it appeared at that time, plate tectonics, which is envisioned as involving gradual changes generated by forces internal to the globe, fully conforms with uniformitarian principles. In contrast, impact processes, which have recently been cited to account for cataclysmic events such as massive tsunami deposits, incinerating wildfires, and global extinctions, carry genuinely revolutionary implications that are fatal to the uniformitarian principle itself."

"In August, 1933, at the in Chicago, was founded with an enrollment of 57 charter members and and as the first President and Secretary-Treasurer, respectively. Within five years, the Society had doubled in size, with members from the U.S.A. and ten other nations. Annual meetings were suspended during World War II (1942 through 1945) and when it reconvened in 1946 the members adopted the name “”. By that time personal and professional antagonisms had arisen that threatened to fragment the Society and led, in 1949, to the resignation of Nininger and his wife. Throughout the 1950s the Society was widely regarded as a small, disorganized and essentially moribund organization. Revitalization of the Society began in the early 1960s after the advent of the when the Society steadily gained members with expertise in , , , and , and impact dynamics."

"Since the opening of the , images from have enabled us to map the surfaces of all the rocky planets and in the Solar System, thus transforming them from astronomical to geological objects. This progression of geology from being a strictly to one that is planetary-wide has provided us with a wealth of information on the evolutionary histories of other bodies and has supplied valuable new insights on the Earth itself. We have learned, for example, that the , and that the Moon subsequently accreted largely from debris of . The airless, waterless Moon still preserves a record of the impact events that have scarred its surface from the time its crust first formed. The much larger, volcanic Earth underwent a similar bombardment but most of the evidence was lost during the earliest 550 million years or so that elapsed before its first surviving systems of crustal rocks formed. Therefore, we decipher Earth's earliest history by investigating the record on the Moon. Lunar samples collected by the of the USA and the of the former USSR linked the Earth and Moon by their oxygen isotopic compositions and enabled us to construct a timescale of lunar events keyed to dated samples. They also permitted us to identify certain meteorites as fragments of the lunar crust that were projected to the Earth by impacts on the Moon. Similarly, analyses of the Martian surface soils and atmosphere by the and s led to the identification of meteorite fragments ejected by hypervelocity impacts on Mars. Images of Mars displayed land-forms wrought in the past by voluminous floodwaters, similar to those of the long-controversial of Washington State, USA. The record on Mars confirmed catastrophic flooding as a significant geomorphic process on at least one other planet. The first views of the Earth photographed by the crew of gave us the concept of and heightened international concern for protection of the global environment."