Almost a month passed between July 5 and August 2, 1993. What happened during these 28 days changed forever the way geologists will look at this quiet Midwestern part of the US. You see, before this time, the spillway at Coralville Reservoir was simply that--a spillway made of pavement sitting idle, quietly waiting. All that changed during "the great flood of 1993." The overflow of the Coralville Reservoir Spillway exposed what is now known to scholars and visitors alike as The Devonian Fossil Gorge.
This area, closely managed by the Army Corps of Engineers, is adjacent to Coralville Dam and McBride Beach, located just north of Iowa City on North Dubuque Street. During the floods, the water level behind the dam rose over 4.5 feet above the spillway of the Coralville Dam. These fast-moving waters carved away pavement, clay, bedrock, and top soil to expose the Devonian-era fossils below. Though the water flowed at a rate of only five to six times the normal rate of the Iowa River, it rushed downhill in such a way that it ultimately carved out of bedrock, a 15-foot gorge showing clearly the layers of fossils below.
The Coralville Lake was authorized under the Flood Control Act of 1938 as a way of controlling the Iowa river and its winding path throughout the area. The basic work on the dam began in 1949 and, according to a guide at the site, was completed in 1958, after a delay in construction because of the Korean War. The Coralville Dam still controls waterflow and offers flood protection to the cities and towns downstream of the Iowa river and, in its almost 40 years of exisitence, has had no problems whatsoever.
For those who may not know, the Devonian era was a time in history of about 375 million years ago and is easily viewed though a horizontal "cut" in the earth exposed by nature's flood waters of 1993. For scholars and visitors alike, to view this world from so long ago is to see it as one might see parts of a layer cake! It is true that if visitors look carefully, individual fossils can be clearly seen embedded within the rock, something unique to any area and seen previously in museums or books. Though this is a unique way to view history, you need to have a smattering of background of the era to fully appreciate all that was exposed during the summer of ’93. Within this area of land, fossils seen include crinoids, coral heads, and even bracheopods, some so perfectly preserved that the individual details are clearly seen without any extra magnification. It is as if they were set ther for all to see and appreciate, or perhaps to remind us that there was life in the area BEFORE people, that this area has many secrets yet to be revealed. Of course, the area must be stabilized to protect both the viewers and the exhibit, so unfortunately many of the best-preserved fossils have had to be covered in order to better preserve the area. Knowing this, the viewer can take comfort in the fact that a large number of the most impressive fossils have been relocated to the visitor center at the top of the hill.
While we are on the subject, be sure to stop at the aforementioned visitor center. Though the climb is in fact steep, this center has an impressive display of fossils found at the gorge and deemed important enough to remove and display here. One impressive fossil has a perfect impression of a sea creature that at one time grew to lengths of over 80 feet--pretty impressive when you remember that today most of the land around this area is planted in corn and other crops, with nary a sign of sea life in sight! It is pretty amazing that this little piece of the Midwest, so quiet and thought boring by many visitors, can have such a wonderful piece of history on display.
Although actions have been taken to preserve this important look into the history of Iowa, there are many occurrences, both natural and man-made, that threaten its existence even today. Freezing and cooling, both of which are common to this area of the Midwest, will tend to chip and break off the rock surface after a time, and the often harsh Iowa winters with their sleet, ice, and heavy snows can take their toll on this piece of history as well. Though winters have been mild since summer of ’93, we Midwesterners know this cannot last forever; we are bound to have the storm of the century, and with these storms come the worries that the change in temperatures can (and most likely will) cause irreversible damage. The various natural growth plants and such also threaten the gorge, for as they grow they expand the rock, causing cracking and possible irreversible damage.
Though these natural threats are worrisome, there is one that is much more so. The greatest threat to the area is not snow, rain, or even plant growth, but the threat of human hands! While it most certainly is tempting to carry away a "nice little fossil" to have a piece of history, the many visitors every year must remember that such "collecting" is illegal. The Army Corps of Engineers have posted signs warning visitors against such action without a federal permit, a warning they have been known to sternly enforce. And if a "warning" is not enough for you, consider the fine involved with removing and item from a national park; these can be quite steep and certainly nothing to play around with!
According to an employee at the site, this gorge dates back to the Middle Devonian period, approximately 375 million years ago. Fossils found here include coral, and it is because of the evidence of this coral that a nearby town, Coralville, was so named. The fossils seen in the 23 exposed beds of the gorge are staggering to the mind and are, in fact, still being discovered and catalogued as this piece is being written. Geologists have spent much of their time at the gorge since it was discovered, simply discovering and identifying the different layers, fossils, and debris found in the gorge. School-age children from miles around regularly make trips to the gorge during the year, learning and discovering alongside professional scholars at the site. To see this gorge is to believe it. To try to explain to someone who has no idea of the area, the expanse of the gorge, or the horrid rains of ’93, it is close to impossible to convey the sheer amazement one feels when first viewing this gorge, realizing all the while that this was alive with sea creatures 375 million years ago. The thought of it is staggering and truly only experiencing the gorge for oneself can you really appreciate it all being photographed for possible use in future texts about the Devonian age. As a teacher I can only encourage any and all who travel to the area to experience this gore for themselves and see the multi-layered history firsthand.
The best time to visit this site is in the spring or fall, as the gorge does not catch many cool breezes. In fact, the limestone that is so common to the area there tends to hold in the hot Iowa sunshine, and anyone who has experienced sun in Iowa can tell you it is best to avoid it if at all possible during the hottest parts of the day. Also, please remember that when you do visit the gorge, you will be doing a fair amount of walking and climbing, so wear loose clothing and comfortable shoes. While it is not for young children, it is common to see young children at the site with parents, but don’t let your children run around. This isn’t a playground, but a museum of sorts and definitely not a play place. The rocks are steep and somewhat hard to climb, so one could easily be hurt if they aren’t careful while viewing the gorge. During the school year, many schools take field trips to the gorge for firsthand lessons, so beware that there may be a crowd during late fall and early spring. And while there are no official guides, there are usually persons present who would enjoy "lecturing" on the finds at the gorge and who will happily share the various finds around the gorge that they have discovered on previous visits. Don’t forget your camera, for while taking the fossils themselves is forbidden, pictures are encouraged, and with digital cameras today, sharing your find is as easy as finding the closest cyber café! Bottom line is this folks: check out this real life slice of history, learn about the gorge, and share it with your kids, your spouse, or that special someone in your life--you don't get chances like this every day.