While balancing on a rocky cliff at the Mississippi River bluffs, University students learned how their footholds formed from where an ocean once flowed.
Students taking Geology 1001 stretched their legs and minds Tuesday as teaching assistants led them through rock structures that make up the University’s East Bank campus.
Walter Library’s immense pillars facing the Mall are made of limestone, said Sarah Smith, one of the TAs, as students scribbled her words onto paper. At a closer look, the limestone contains broken, tiny shell fossils.
Covering the bottom of the shallow ocean that once flowed over Minnesota’s landscape, the shells broke up and scattered. Rocks and debris compressed the broken shells, forming limestone over the years, said Jason Erickson, another TA.
Students learned how rocks such as limestone formed before their field trip. This is just a chance to apply their knowledge to their surroundings, Smith said. She said Tuesday was the first time they took the class out of the classroom this year.
“I’ve always wondered walking around here, ‘What is that? What are those borders made out of?'” said Sarah Jacobson, College of Liberal Arts junior.
Pillsbury Hall, home of the geology department, is a rock collection in and of itself. The large bricks forming the building are made of sandstone.
A column on the northwest side of Pillsbury is made of Ely Limestone, formed in Ely, Minn., more than 2.7 billion years ago. Sitting outside the building is a large piece of Oneota Dolomite with pock marks caused by water erosion.
Although the TAs told their students what formed each building, bench or pillar, students also learned how to figure it out themselves.
“If you put acid on limestone it will fizz,” said Brian Artka, an Institute of Technology sophomore. Besides the diluted hydrochloric acid test, geologists look at a rock’s cleavage — the way it breaks — to figure out what type it is.
After their East Bank stroll, students hiked the narrow Mississippi River bluffs. There they saw evidence of the ocean’s changing tides imprinted on the remaining rocks.
Three distinct layers make up the bluffs’ wall, signifying the rise and fall of the ocean, said Erickson while picking up a handful of St. Peter Sandstone.
“This should just be called sand, really,” Erickson said as the crumbly, yellow substance slid through his fingers. Students carefully milled around him on the loose rock to grab their own handful and take in the history of their surroundings.