Mammoth Spring is the largest spring in the state of Arkansas, the second largest in the Ozark Mountains region, and the seventh largest in the United States. This National Natural Landmark is located within the boundaries of Mammoth Spring State Park. Approximately 497 feet from the Missouri state line in north-central Arkansas, it is within sight of U.S. Highway 63 and the city of Mammoth Spring (Fulton County). Though the spring has always been known as “big” or “mammoth,” the first known settlers in the 1820s created a small village called “Head of the River,” which would later be renamed Mammoth Spring.
Water flows from the spring at an average rate of 9.78 million gallons per hour, with a constant water temperature of fifty-eight degrees Fahrenheit. It measures eighty feet deep at the head of the spring; twenty feet of that is a vertical underwater bluff. Though the actual spring cannot be seen from the surface because of the depth of the pool, it resembles a funnel with a bent tube featuring a forty-five-degree angle. The water from the spring forms a ten-acre lake known as Spring Lake and flows south as the Spring River, one of state’s best-known rivers for trout fishing and recreational floating.
A spring is a natural flow of water that serves as an outlet for water that has accumulated in the permeable rock strata underground. Rainwater soaks into the soil and is drawn downward by gravity into openings, or fractures, in the limestone, in the process forming underground channels or caves. Once these spaces have become completely saturated with water, an outlet must be found, leading to the formation of a spring. Local folklore regarding the creation of Mammoth Spring includes the tale of a Native American tribe that was suffering through a great drought. The chief’s son died, and in a fit of despair the chief executed the tribe’s warriors. As a mass grave for them was dug, water gushed forth from the ground, thus forming Mammoth Spring.
Rainwater from the high, flat plateau areas in southwestern Missouri, from Thayer north to Pomona, is the water source for Mammoth Spring. The rainwater soaks down through the clay soils and fractured limestone deposits until it reaches the underground water table. From there, it flows along a vast underground system of interconnected cavities, eventually converging into a main artery that emerges in the spring pool at Mammoth Spring. At times, the spring pool is noticeably bubbly, a condition attributed to the high levels of minerals such as calcium and magnesium.
As a bottom-fed spring, Mammoth Spring supplies a consistent level of water year round to both Spring Lake and the Spring River. Because of the cool temperature and steady water supply, two fish hatcheries are located near the spring to provide fish for stocking the Spring River. The first of these is the oldest national fish hatchery in Arkansas, the Mammoth Spring National Fish Hatchery (MSNFH), which was established in 1903 and is operated by the U.S. Fish and Wildlife Service. In addition, the Jim Hinkle Spring River State Fish Hatchery is operated by the Arkansas Game and Fish Commission.
For additional information:
Mammoth Spring State Park. http://www.arkansasstateparks.com/mammothspring/ (accessed October 27, 2021).
U.S. Geological Survey Data from the Mammoth Spring Gauging Station. waterdata.usgs.gov/ar/nwis/uv/?site_no=07069190&PARAmeter_cd=00065,00060 (accessed October 27, 2021).
Dianna Owens Fraley
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In the fall of 1966, while I was a student at Memphis State University in Memphis, Tennessee, a friend of mine and I scuba dived into the Mammoth Spring pool in an attempt to penetrate the spring itself. We did manage to get to the opening of the spring at about eighty feet deep, but the force of the water was so tremendous, we could get no farther than the opening at the base of the vertical rock wall in the northwest corner of the spring pool next to Hwy. 63. I remember the visibility was only about three or four feet, even with powerful diving lights. I remember seeing gravel on the bottom literally boiling from the force of the water. I lost a diving knife somewhere in the pool that day and I presume it’s still down there. I look back on that attempt as a foolhardy adventure of youth and hope no one ventures into that dangerous place again. Once was enough for me.