Effects of The Mason Impact Structure

The Manson event was an unimaginable catastrophe. The impact of the enormous meteorite caused destruction equivalent to approximately 10 trillion tons of TNT. Everything within 130 miles of the point of impact was instantly engulfed in flames. Trees were toppled and standing vegetation was devastated within 300 miles of the impact site. It is also believed that most animals as far as 650 miles away did not survive the Manson impact, and dinosaurs 800 miles away would have been knocked off their feet.

The Western Interior Seaway was home to many forms of marine vertebrates, which would have been greatly disturbed or killed by giant shock waves and possible tsunami-like waves. The seaway’s habitats would have been so disrupted as to cause the death of thousands of marine creatures. To support this theory, scientists have found evidence that certain lineages of fish, mosasaurs and marine turtles, including the Archelon, mysteriously vanished from the Western Interior Seaway during the approximate time of the Manson impact event.

Researchers believe that the region stabilized a short time after the impact, and that a shallow lake formed in the crater moat. In time, the lake filled with dirt and rocks. The area was leveled by more than 70 million years of erosion that followed. Due to the crater’s thick covering of Phanerozoic clast breccia, only small areas of the central peak and terrace terrane eroded. The Manson area was covered by several continental glaciers during the last 2.5 million years, causing further erosion and burying the region in layers of glacial till. Today, the crater is entirely covered with glacial sediment and not detectable above ground.

Although groundwater is difficult to find within the Manson Crater, the structure has brought several benefits to local residents. According to Dr. Raymond Anderson, Supervisor of Geology and Mineral Resources at the State of Iowa Department of Natural Resources, Energy and Geological Resources Division, "Water wells that penetrate into the brecciated crystalline rocks of the central peak encounter naturally soft water. On the northeast edge of the structure, at the town of Gilmore City, gigantic limestone quarries mine limestone that was lifted up to the current land surface by the force of the Manson impact."