The arch at the Time Sweeps sculptureStudents Mallory Osmun and Tara Lonsdorf created this interactive geology analysis of Thea Alvin’s Time Sweeps sculpture. The students describe Time Sweeps as the rockiest public art to hit the Rowan University Glassboro campus. Envisioned as an outdoor classroom, amphitheater, and communal meeting area, the sculpture’s construction is a product of the technical precision and creative artistry of master stonemason Thea Alvin, who first immersed herself into the world of stonework at the age of just 16. Ms. Alvin launched the construction process in May and June 2021 with the help of three assistants and several Rowan students from the Departments of Art and Geology.

This sculpture’s features include a hollow basalt beam, which acts as a solar calendar angled to capture the first rays of light cast by the summer solstice. The sunrise will filter through the hole and be cast dramatically upon the basalt pillars on the other side of the sculpture, signaling the beginning of summer.

A photo of a Gabbro rock located at the Time Sweeps sculpture.Showcased along with the arch are seven different boulders representing the three major rock groups that make up the planet and show its amazing geological diversity. The basalt, rhyolite, gabbro, and granite make up the igneous group of rocks and tell us the story of the Earth’s mantle. The conglomerate and arch give a sedimentary history of ocean environments, and the schist and gneiss show the range of metamorphism in tectonic regions. With these boulders on display, visitors and students gain opportunities to see parts of our planet otherwise impossible to experience inside of South Jersey. 

Mallory and Tara’s project provides a detailed geology analysis of the Time Sweeps and photographic examples that can help students learn about the major rock groups. Please use the following link to explore the project:



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