Rock Show

Construction crews are jackhammering away limestone that formed millions of years ago.
Construction crews are jackhammering away limestone that formed millions of years ago.

In the distant past, the current site of Bloomington, Ind., sat on the floor of a shallow sea about 15 degrees south of the equator. Brachiopods, bryozoans and crinoids—three marine animals that resembled a clam, a coral stalk, and a plant-like stem respectively—thrived in the area.

As they are wont to do, those three animals (and many more) died, and over the years the shells and bones of the deceased mixed with sediment and minerals that created the crystal form of calcium carbonate. The mixture created a specific kind of rock called Salem limestone. As the years passed, the continent of Africa collided with North America, forming the Appalachian Mountain range, and the shallow sea was drained, exposing the Salem limestone to the elements. Plate tectonics moved the future state of Indiana from the equator to the northern hemisphere and its current position.

And after 350 million years in the ground, construction workers are cursing its existence.

If you’re a fan of the sound of jackhammers, boy, do we have a site for you. The construction of Luddy Hall always included the removal of limestone from the site. You can’t build anything in Monroe County and not run into a lot of limestone. The problem is that the exact spot where an elevator shaft is supposed to be built happens to be the 350-million-year-old home of a deep vein of Salem limestone, and construction crews will spend the next three weeks jackhammering the stone out of the ground.

It’s hard, loud, dusty work, but it’s a necessary part of the construction project. The good news is the rock still has a bright future, or as bright of a future as rock can have. Because limestone is a commodity, some of it will be used as clean fill for the construction of the nearby I-69 project. That gravel you see on construction sites? The large rocks used to build up the banking around bridges? That’s limestone.

Over the next few weeks, the Luddy Hall site will see mass excavating, and the Weddle Bros. construction team will be doing the subgrading for the floor and beginning work on the exterior footings. That means arrival of rebar and concrete trucks are still a couple of weeks away, but they’re getting closer.

Pelli Clarke Pelli, the architects on the project, and representatives from Weddle Bros. enjoyed a tour of some local quarries and picked out samples of different grades of limestone that will make up the exterior of the building.

If you’re interested in seeing the work being done at the Luddy Hall site, check out the construction cam that is mounted on the top of the nearby Geology Building that gives a clear view of the site.

Special thanks to Polly Sturgeon, the Education Outreach Coordinator for the Indiana Geological Survey at IU, for her help in telling the story of Salem limestone.

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