Imagine standing at the edge of a colossal abyss. That is the immensity of Thornton Quarry. It is one of the largest aggregate quarries on Earth.
Thornton Quarry’s story is one of time. It stretches back hundreds of millions of years. It’s also about human endeavor and engineering marvel.
The first settlers arrived in Thornton in 1834. Gurdon Hubbard opened the first quarry in 1836. That quarry was on Kinzie Street. It was abandoned due to poor quality stone. Fred Gardner and Stephen Crary opened quarries later. The Brownell Improvement Company purchased the area in the early 1900s. Colonel Hodgkins bought the property in 1920.
The quarry north of Ridge Road opened in 1924. A tunnel connected the north and south quarries in 1926. Colonel Hodgkins died. Brownell repurchased the quarry. Material Service Corporation purchased it in 1938. It has been the owner ever since.
The sheer size of the Thornton Quarry is impressive. It spans 1.5 miles long and 0.5 miles wide. The deepest point plunges 450 feet down. The entire village of Thornton could fit on its floor.
But there is also a hidden history in its rocks. Crushed limestone reveals evidence of the distant past. Fossils of ancient sea creatures tell a story. This was once an equatorial tropical reef. It existed 600 million years ago. Illinois and Indiana were pushed north by tectonics later.
During the Silurian Period 425 million years ago, North America was different. A shallow, tropical sea covered much of the land. Reefs grew in the area of Wisconsin and Illinois. These reefs were built by organisms. They rose above the seafloor. Warm, shallow waters fostered their growth. The water was clear allowing sunlight to reach the reef surface.
The Thornton Reef teemed with life. Strange marine invertebrates flourished. Corals, crinoids, and shelled creatures thrived. Sea lilies and horseshoe crab-like animals were present. There were ancestors of squids and octopuses. Some were up to ten feet long. Pentamerid brachiopods were common. These fossils are easy to find today.
Coral processed seawater. It created lime deposits. These hardened into limestone. Dead coral remained on top. New coral laid eggs on the limestone. This process repeated itself. The result was layers of limestone. They encased coral and other sea life.
The Thornton Quarry also holds a cosmic secret. A meteorite was found in 1994. It was estimated to be 4 to 4.6 billion years old. It weighed between 800 and 1,000 pounds. It landed when the quarry was a coral reef. That was part of a huge temperate sea. This sea was similar to the Caribbean Sea.
Today, Hanson Material Service owns the quarry. It is the second-largest commercial stone quarry worldwide. It produces aggregates, stone, sand, and other products. The quarry produces millions of tons of rock products each year. The rock is sold as is or ground into dust. It is used in concrete mixing and asphalt coatings. By-products include asphalt shingles and building materials.
The Metropolitan Water Reclamation District contracted to use the Thornton Quarry for stormwater overflow. It is part of the Deep Tunnel project. The quarry supplies billions of gallons of stormwater storage. This water is treated before release into waterways. It protects residents and saves millions in damages.
As we stand here, it’s amazing to consider the transformations. Thornton Quarry is a natural wonder. It is a testament to time. It is a vital part of our modern infrastructure.