The society has six regional sections in North America, an international section, and seventeen specialty divisions.
GSA began with 100 members under its first president, James Hall. Over the next 43 years it grew slowly but steadily to 600 members until 1931, when a $4 million endowment from 1930 president R.A.F. Penrose, Jr. jumpstarted the GSA's growth. As of April 2013, GSA has more than 25,000 members in over 100 countries.
The stated mission of GSA is "to advance geoscience research and discovery, service to society, stewardship of Earth, and the geosciences profession". Its main activities are sponsoring scientific meetings and publishing scientific literature, particularly the journals Geological Society of America Bulletin (commonly called "GSA Bulletin") and Geology. A more recent publication endeavor is the online-only journal Geosphere. In February 2009, GSA began publishing Lithosphere. GSA's monthly news and science magazine, GSA Today, is open access online.
Annual meetings consist of oral and poster presentations about geology, along with field trips, short courses, and other activities. Another big part of the annual meeting is the Exhibit Hall, which includes the Graduate School Information Forum and booths for companies, suppliers, other geoscience organizations, and purveyors of goods and services.
As the need arises, GSA issues Position Statements "in support of and consistent with the GSA's Vision and Mission to develop consensus on significant professional, technical, and societal issues of relevance to the geosciences community. Position Statements, developed and adopted through a well-defined process, provide the basis for statements made on behalf of the GSA before government bodies and agencies and communicated to the media and the general public."
For example, in 2006, the GSA adopted the Position Statement Global Climate Change:
The Geological Society of America (GSA) supports the scientific conclusions that Earth’s climate is changing; the climate changes are due in part to human activities; and the probable consequences of the climate changes will be significant and blind to geopolitical boundaries. Furthermore, the potential implications of global climate change and the time scale over which such changes will likely occur require active, effective, long-term planning.