page_title: Boiling Springs, Pennsylvania
section_title: Hydrogeology
hierarchical_section_title: Boiling Springs, Pennsylvania / Hydrogeology
caption_attribution_description: English: the freakin bubble Boiling Springs
context_page_description: Boiling Springs is a census-designated place in South Middleton Township, Cumberland County, Pennsylvania, United States, and is part of the Harrisburg metropolitan area. The population was 3,225 at the 2010 census, up from 2,769 at the 2000 census.
context_section_description: Boiling Springs is located on the eastern side of South Middleton Township at 40°09′25″N 77°07′57″W, on the north side of Yellow Breeches Creek. Pennsylvania Route 174 passes through the town as 1st Street and leads 8 miles (13 km) northeast to Mechanicsburg and west 22 miles (35 km) to Shippensburg. Carlisle, the Cumberland County seat, is 6 miles (10 km) to the northwest via Front Street/Forge Road.
  According to the United States Census Bureau, the CDP has a total area of 2.48 square miles (6.43 km²), of which 2.47 square miles (6.39 km²) is land and 0.01 square miles (0.03 km²), or 0.49%, is water.
  Boiling Springs gets its name from the natural artesian well springs located in and around the town. Boiling Springs ranks seventh in size of springs in the Commonwealth of Pennsylvania. The largest of these springs named "the Bubble" is a 2nd magnitude spring based on its average discharge of around 0.7 cubic meters per second. About 22 million US gallons (83,000,000 l) of water flows per day from a total of 30 springs dotted across approximately 2 acres (8,100 m²).
  The impression of "boiling" does not result from the temperature of the water, which stays at 55.5–55.8 °F (13.1–13.2 °C) year-round, but rather from a unique hydrogeological feature. Two vertical diabase dikes, made up of highly impermeable igneous basalt parent rock, cut through the limestone bedrock in the area and form a subterranean "V", with Boiling Springs located at the interior tip of the V.
  The dikes were formed around 200 million years ago, during the late Triassic and early Jurassic periods, when Pangaea broke apart: the same period of geological activity that formed the Palisades Sill. What is now eastern North America began to separate from what is now north-western Africa. Deep faults formed in the earth's crust as the continental sections pulled apart. Magma was generated through decompression melting, and this molten rock pushed up to fill the faults. The cooler temperatures of the upper crust quickly solidified the hot rock, preventing it from reaching the surface. This geological process created large, thin, subvertical sheets of impermeable basalt, or diabase dikes.
  When precipitation flows down South Mountain, a large amount of groundwater is produced. Much of the water, which has an acidic pH, is able to erode the valley's limestone bedrock and continue flowing at about 45 feet (14 m) below the soil. However, some of the water is trapped by the impermeable diabase dikes, which act as a hydrologic barrier. The water becomes progressively confined by the dikes as it nears the tip of the "V". Due to the positive pressure created by this confinement, water is pushed up to the surface and out of the artesian aquifer, giving the impression of "boiling" springs. The springs have a median flow of 11,500 US gallons (44,000 l) per minute. These springs, collectively known as a "spring swarm" discharge 5 to 7 times the expected infiltration given its topographic watershed. Data collected via the use of highly precise and accurate data loggers have revealed the springs hydrograph to display discharge surges, while temperature, conductivity, and turbidity remain constant. Water temperature varies seasonally by 0.3 °C but is 6 months out of phase with air temperature. A new model that has been proposed to account for these findings suggests that the excess water emanating from the springs originates from an area 60 km to the southeast on the southern side of South Mountain near the West Conewago Creek, Lat 40`04'56", long 76`43'13".
  One of the most prominent springs in this area is called the "Bubble". It is located directly behind the Boiling Springs Tavern, at the intersection of 1st Street and Front Street. The name of the Boiling Springs High School mascot, "The Bubblers", was inspired by this spring.
caption: The Bubble
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