The Trinity Test and Trinitite

Nicole Summersett
March 13, 2018

Submitted as coursework for PH241, Stanford University, Winter 2018


Fig. 1: A sample of Trinitite left behind from the detonation. (Source: Wikimedia Commons)

By early 1939, the secret of splitting a uranium atom was known throughout the world. With this revelation came the realization that utilizing this energy could produce a highly destructive bomb. With this new information as well as the threat of a second world war, the United States started developing plans to produce an atomic bomb. In late 1941, these efforts to build an atomic bomb became known as the Manhattan Project. [1] The Manhattan project eventually led to the first atomic bomb being set off in the United States and helped sparked the nuclear age, which has forever impacted the world. Although it was not known what the exact results or environmental impact of this first test would be, the results dramatically helped scientist research both the immediate and long-term effects of nuclear detonations.

The Trinity Test

On July 16, 1945, the first atomic bomb, Gadget, was set off in Alamogordo, New Mexico approximately 120 miles south of Albuquerque. The plutonium bomb was detonated with a yield of 21 kilotons which was approximately equal to the Fat Man atomic bomb dropped on Nagasaki. [2] The resulting temperature from the fireball was estimated at 8430°K, which is about 1.5 times hotter than the surface temperature of the sun. The mushroom shape cloud that followed the explosion erupted to a height of between 15.2 to 21.3 kilometers. [3] A five-foot deep, thirty-foot wide crater was left at ground zero. All structures in the immediate path were destroyed.

A radioactive green glass residue was also discovered at the site of the test, shown in Fig. 1. It was given the name trinitite. [4] Trinitite has facilitated studies of the impact of nuclear blasts on the environment and the radioactive material left behind.


Left at the test sight of the Gadget was a green glassy material later known as trinitite - named after the Trinity mission. This new material was one of the first items available to be studied for radiation due to a nuclear explosion. Research done on trinitite has shown that it has been found to contain fission products, activation products, and residual nuclear fuel. [5] While sand is composed of quartz, microcline, abite, muscovite, actinolite, and calcite, only quartz was found in the glass left behind - inferring that all other materials had been melted away. [3] The trinitite is quite radioactive. The radioactive nuclides include: plutonium and uranium from the bomb, fission fragments, and the activation products that were produced by the bomb's neutrons. [3] Interestingly enough, not all of the trinitite was formed by the melting of sand. [5] The top layer of trinitite glass found was formed when the hot gasses rose and then rained down to the earth as molten droplets. That is why the trinitite was formed in a bead shape. This trinitite is more radioactive than the trinitite formed from the melting on the surface.


Sixty-five years after the Gadget was detonated, the trinitite glasses are still slightly radioactive. The radiation at the test sight is about ten times greater than the radiation in the surrounding areas. [4]


The Trinity nuclear test was not only the beginning of a nuclear age, but also provided much-needed information on how nuclear test change the surrounding environment and what role radiation plays in the environment.

© Nicole Summersett. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] H. Goldwhite,"The Manhattan Project," J. Fluorine Chem. 33, 109 (1986).

[2] Fahey, A. J., et al. "Postdetonation Nuclear Debris for Attribution," Proc. Natl. Acad. Sci. (USA) 107, 20207 (2010).

[3] N. Eby et al., "Trinitite - the Atomic Rock," Geology Today 26, 180 (2010)

[4] C. Ukropina, "The Trinity Test," Physics 241, Stanford University, Winter 2015.

[5] G. R. Eppich et al., "Constraints on Fallout Melt Glass Formation from a near-Surface Nuclear Test," J. Radioanal. Nucl. Chem. 302, 593 (2014).