She was a leading figure in the use of microfossils to determine the age of rock formation for use in oil exploration in the Gulf of Mexico region.

Additionally, her contribution to geology and the study of micropaleontology was pivotal in earning women geologists respect in the field.

[3] Richards attended the University of California, Berkeley, graduating in 1919 with an honors degree in paleontology, geology, and physiography.

[3][4] In 1920, she left California and moved to Houston to work for the Rio Bravo Oil company, where she was hired by Edwin T.

[3] In 1921, Applin presented a paper in Amherst, Massachusetts, stating her theory that microfossils could be used in oil exploration, specifically the dating of the rock formations in the Gulf of Mexico region.

[8] In 1925, Applin co-authored a paper with Alva C. Ellisor and Hedwig Kniker,[3] which reported her findings that oil-bearing rock formations in the Gulf Coast region could be dated using microfossils.

[11] During a 1955 survey in the South-East Gulf Coast region of the United States, Applin discovered 4 previously undiscovered species of Foraminifera that helped in piecing together prehistoric environmental conditions in Alabama, Georgia, and Florida[12] In 1960, Applin received a plaque from the Gulf Association of Geological Studies in recognition of her accomplishments and contributions to the field.

[3] By 1975, Edgar Wesley Owen wrote Trek of the Oil Finders, minimizing the role that Esther and her fellow female paleontologists played in the discovery.