Marr's Spring EarthCache

Marr's Spring Earthcache

"Part of Marr's Field on farmland owned by William Marr, this spring was a major factor in the selection of this site for the University of Alabama campus in 1827.  From its opening in 1831 well into the 20th century, the institution relied upon Marr's Spring as its principal water source.  Water flowing from hillside crevices was collected in these brick cisterns and hauled in buckets to the rooms of students and throughout the campus.  A dam for a swimming pond and bathhouse was constructed, supported by the spring and cisterns.  By the mid-1880s, as the cisterns began to deteriorate, the University considered repairs until deciding, as the 1889 trustee's minutes recorded, "It has always been considered doubtful whether the plunging and swimming in the very cold water so directly from the spring is conducive to health."  A 1955 survey found that Marr's Spring yielded 100 gallons of good, clear odorless water per minute.  The cisterns were renovated in 2010 in an effort to restore the original beauty of this University of Alabama historical landmark." -- from historical marker.

What is the difference between a spring and an artesian well?

A spring occurs when groundwater appears at the land surface. Springs occur in various forms and are classified by the rock type in which the spring occurs, how the spring was formed, how much water flows from the spring, the temperature of the water, and if the water flow varies from season to season. Some springs may fall into more than one classification.

ARTESIAN SPRINGS occur when the groundwater, under pressure, finds its way to the land surface. An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well. Water may even reach the ground surface if the natural pressure is high enough, in which case the well is called a flowing artesian well. An aquifer is a geologic layer of porous and permeable material such as sand and gravel, limestone, or sandstone, through which water flows and is stored. An artesian aquifer is confined between impermeable rocks or clay which causes this positive pressure. The recharging of aquifers happens when the water table at its recharge zone is at a higher elevation than the head of the well. Fossil water aquifers can also be artesian if they are under sufficient pressure from the surrounding rocks. This is similar to how many newly tapped oil wells are pressurized. Artesian wells were named after the former province of Artois in France, where many artesian wells were drilled by Carthusian monks from 1126.

GRAVITY SPRINGS are formed by water soaking into the ground until the water encounters a confining layer that will not let the water seep further down. The water then flows across the top of the confining layer until it reaches the ground surface. Examples of gravity springs are springs found in hillsides or cliffs. The springs along the north shore of Lake Superior and along the Mississippi and St. Croix River Valleys are generally of this type.

PERENNIAL SPRINGS drain a large land surface area and flow continuously throughout the year.

INTERMITTENT SPRINGS flow only during certain times of the year when rainfall or snowmelt is sufficient to recharge the soil and groundwater.

TUBULAR SPRINGS are most commonly associated with limestone channels and cavern, and volcanic lava tubes. The water is contained in caves or solution cavities in the limestone, or hollow “tubes” formed by cooling lava. Cavities or tubes may range from microscopic in size to large openings measuring many tens of feet across. Large tubular springs in some parts of the United States flow over a million gallons per minute. The large springs of southeastern Minnesota are tubular springs.

SEEPAGE SPRINGS are formed when groundwater slowly seeps out of the ground. Seepage springs usually occur in sand, gravel, or organic materials and generally are found in depressions or valley bottoms. Seepage springs are different from artesian springs because they are not necessarily confined (contained below a dense layer of clay or other material) and usually have low flows.

THERMAL SPRINGS are springs that release groundwater warmer in temperature than groundwater in the surrounding watershed area. Examples of thermal springs are warm springs, hot springs, mudpots, and geysers such as those at Yellowstone National Park. Thermal springs are most commonly found in areas with a recent history of volcanic activity.

Springs are often confused with flowing artesian wells. An artesian well is a hole or boring that has been drilled into a water-bearing formation or "aquifer" that is under pressure. The water in an artesian well rises above the top of the aquifer (water-bearing formation) until the pressure is equalized. In a flowing artesian well, the water rises above the ground surface and the water flows out of the well casing to equalize the pressure.

So why is this spring here?

As with many geological questions in this area of the Black Warrior Basin, it goes back to the Pottsville Formation.

The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, and Ohio. The formation is also recognized in Alabama. It is a major ridge-former in the Ridge-and-Valley Appalachians of the eastern United States. The Pottsville Formation is conspicuous at many sites along the Allegheny Front, the eastern escarpment of the Allegheny or Appalachian Plateau. Relative age dating of the Pottsville places it in the early to mid-Pennsylvanian period, or roughly 300 million years ago. During this geological period, much of what is now the central United States was covered by a shallow sea, the Rocky Mountains did not yet exist, and the Appalachians were much higher than today.

The Pottsville Formation consists of a gray conglomerate, fine to coarse-grained sandstone, and is known to contain limestone, siltstone and shale, as well as anthracite and bituminous coal. It is considered a classic orogenic molasse. The formation was first described from a railroad cut south of Pottsville, Pennsylvania.

The term "molasse" refers to the sandstones, shales and conglomerates formed as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse is deposited in a foreland basin, especially on top of flysch, for example that left from the rising Alps, or erosion in the Himalaya. These deposits are typically the non-marine alluvial and fluvial sediments of lowlands, as compared to deep-water flysch sediments. Sedimentation stops once the orogeny stops, or once the mountains have eroded flat. The molasse can sometimes completely fill a foreland basin, creating a nearly flat depositional surface, that nonetheless remains a structural syncline. Molasse can be very thick near the mountain front, but usually thins out towards the interior of a craton; such massive, convex accumulations of sediment are known as clastic wedges.

In Alabama, the term "Fall Line" is used to describe the locations upstream that major rivers (Black Warrior, Cahaba, Coosa and Tallapoosa) were no longer navigable before the construction of locks and dams. The University of Alabama lies to the south of this line, which approximates the boundary between the Atlantic Plain and the Appalachian Highlands. As one moves south and west into the Black Warrior River basin, the Pottsville formation rocks that are exposed to the north and east begin to be covered with angular unconformity by poorly consolidated Mesozoic (252-66 million years ago) and Cenozoic (66 million years ago to present) strata of the Gulf Coastal Plain and Mississippi Embayment.

In this particular location, rains that fall in the University of Alabama and surrounding area pass through the layers of surface strata as well as the sandstone and shale below ground until they reach a layer through which they cannot easily pass. That water flows below the campus until the water table is exposed at Marr’s Spring, where it emerges from the ground continually year-round.

To log this earthcache, you must answer the following questions. The answers can be found by observation, reading the historical marker, and reading this cache page.  Send them to me via my email address on my profile. Do not post them to your log or it will be deleted.

1. How many cisterns are at the site?

2. Why was this site important to the formation of the University of Alabama?

3. How many gallons of water, per minute, did a survey find that Marr's Spring produced?  When was the survey performed?

4. What type of spring do you think this is, based on the information above? Could it be more than one type? Give evidence for your answer.

5. (Optional) Take a photo of yourself (or your GPS) at this picturesque site!

If you enjoyed this cache, please give it a Favorite ribbon!