Imagine you took a stack of ribbons, compressed it till it buckled into bows, and then tilted the whole stack on its side. That pretty much sums up what you can see in this picture of plunging, folded bedrock at Gulpha Gorge Campground, north of Hot Springs, in the Ouachita Mountains of Arkansas. The bedrock of the Ouachitas was buckled and tilted about 200 million years ago when the South American and North American continents collided – part of the incredible process geologists call plate tectonics.
This is just a couple of wee folds that are exposed at the surface because the bedrock at Gulpha Gorge is novaculite – a really hard rock that doesn’t erode away easily. However, if we could strip the vegetation and civilization away in central Arkansas, we would see that pretty much all the rocks in the region are folded and tilted in similar ways. Some of the folds cover many square miles and can be seen from space on a clear day, and others are no bigger than a speed-bump.
Pictured above is one of the “gold” mines of Arkansas. This is one of many prospect holes dug in the Ouachita Mountains around 1886 when investors fell victim to the first documented Arkansas gold scam. It’s located in the Charlton Campground just west of Mt. Ida in the Ouachita Mountains. The reality is no gold in commercially minable quantities has ever been found in Arkansas.
Scams involving gold and other precious metals are not unique to the state, but they have been a recurring problem, as recently as the mid 1980s. The scams, in a nutshell, consist of staking out a claim on a piece of land, obtaining falsified assay reports that show inflated values of precious metals, and then duping investors into buying parts of the claim.
Though it’s hard to imagine falling victim to such a scheme, the con-men have historically been quite successful. As rumors spread, more and more people rush to get in on the bonanza. By the time the dust starts to settle, the original instigators are gone and so is everyone’s money.
This is a picture of petrified wood. Most people are familiar with famous petrified wood occurrences, such as the Petrified Forest National Park in Arizona. We also have this curious fossil in Arkansas.
Petrified wood, like other fossils, forms when minerals replace the organic material that makes up an organism – in this case a tree. For this to happen the tree has to be buried very quickly, while alive or immediately after dying, because oxygen causes things to rot. Burial can result from a landslide, volcanic ash fall, or other natural process. After burial, mineral-rich groundwater slowly replaces the organic tissue, most commonly with the mineral quartz.
The result is a solid rock that looks exactly like a piece of wood, often retaining growth-rings and other fine details of the original plant. Petrified wood in Arkansas is young geologically speaking. It formed in the past 66 million years.
The above picture shows several varieties of kryptonite…. not really! These are various minerals that display a natural phenomenon known as fluorescence. Fluorescent minerals contain particles that glow when exposed to ultraviolet light, a type of light outside of the spectrum of light we can see. Actually, these minerals also fluoresce in visible light such as sunlight, but the visible wavelengths drown out the glow so we don’t notice it.
This collection of fluorescent minerals, along with other educational, geology-related exhibits, is on display at the Arkansas Geological Survey’s learning center in Little Rock. If you would like to visit the learning center and see for yourself, it’s available for touring by appointment. You can find out more by contacting the Arkansas Geological Survey.
This week’s geopic is a bit of a stretch, but since ice is technically a mineral, a frost flower is a crystal form of the mineral ice. Plus they are just cool.
Frost flowers form when the air is below freezing but the ground isn’t frozen. In Arkansas, these conditions typically occur early in the morning in Fall or Spring. They begin due to freezing of moisture in the stem of a plant which expands and makes small cracks in the stem. Water in the plant freezes as it is extruded from the cracks, and more moisture is continually wicked up from the soil. The resultant ice forms delicate ribbons that curl around the stem resembling flower petals.
Because they are so fragile and rarely last more than a few hours, most frost flowers are never seen. If you happen to be out on a crisp morning, come across one, and you have a camera handy, be sure to take some pictures.