Editing Boiling Springs, Pennsylvania (section)

==Hydrogeology==
Boiling Springs is located on the eastern side of South Middleton Township at {{coord|40.156884|-77.132609|type:city_region:US|format=dms|display=inline}},<ref name="GR1">{{cite web| url=https://www.census.gov/geographies/reference-files/time-series/geo/gazetteer-files.html| publisher=[[United States Census Bureau]]| access-date=2011-04-23| date=2011-02-12| title=US Gazetteer files: 2010, 2000, and 1990}}</ref> on the north side of [[Yellow Breeches Creek]]. [[Pennsylvania Route 174]] passes through the town as 1st Street and leads {{convert|8|mi|0}} northeast to [[Mechanicsburg, Pennsylvania|Mechanicsburg]] and west {{convert|22|mi}} to [[Shippensburg, Pennsylvania|Shippensburg]]. [[Carlisle, Pennsylvania|Carlisle]], the Cumberland County seat, is {{convert|6|mi|0}} to the northwest via Front Street/Forge Road.

According to the [[United States Census Bureau|U.S. Census Bureau]], Boiling Springs has a total area of {{convert|6.43|km2|order=flip}}, of which {{convert|6.39|km2|order=flip}} is land and {{convert|0.03|sqkm|order=flip|2}}, or 0.49%, is water.<ref name="Census 2010"/>

Boiling Springs gets its name from the natural [[artesian well|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.<ref name="ReferenceB">{{Cite journal |doi = 10.1002/2017GL073790|title = Correlating Global Precipitation Measurement satellite data with karst spring hydrographs for rapid catchment delineation|journal = Geophysical Research Letters|volume = 44|issue = 10|pages = 4926–4932|year = 2017|last1 = Longenecker|first1 = Jake|last2 = Bechtel|first2 = Timothy|last3 = Chen|first3 = Zhao|last4 = Goldscheider|first4 = Nico|last5 = Liesch|first5 = Tanja|last6 = Walter|first6 = Robert|bibcode = 2017GeoRL..44.4926L|doi-access = free}}</ref> About {{convert|22|e6USgal|L}} of water flows per day from a total of 30 springs dotted across approximately {{convert|2|acre|sqm}}.

The impression of "boiling" does not result from the temperature of the water, which stays at {{convert|55.5-55.8|F}} year-round,<ref name="ReferenceB"/> but rather from a unique hydrogeological feature. Two vertical [[diabase]] [[Dike (geology)|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.<ref>Flippo, H. N., Jr. [1974], ''Springs of Pennsylvania'', Pennsylvania Department of Environmental Resources, Office of Resources Management, Water Resources Bulletin 10, 46 p.</ref>

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 [[Fault (geology)|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.<ref>{{cite web |url=http://www.priweb.org/ed/TFGuide/NE/topo/topo_files2/topo_pdfs/ne_topo2.pdf |title=Archived copy |access-date=2009-09-01 |url-status=dead |archive-url=https://web.archive.org/web/20080910102047/http://www.priweb.org/ed/TFGuide/NE/topo/topo_files2/topo_pdfs/ne_topo2.pdf |archive-date=2008-09-10 }} Paleontological Research Institution, "Topography of the Appalachian/Piedmont: Region 2", p. 117</ref>

When precipitation flows down [[South Mountain (Maryland and Pennsylvania)|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 {{convert|45|ft}} 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 {{Convert|11500|USgal|l}} per minute. These springs, collectively known as a "spring swarm" discharge 5 to 7 times the expected infiltration given its topographic watershed.<ref>Becher, A. E. (1991), Stop 7; Hydrogeology and the source of Boiling Springs, Cumberland County, Pennsylvania, in Geology in the South Mountain Area, Pennsylvania: Guidebook for the 56th Annual Field Conference of Pennsylvania Geologists, edited by W. D. Sevon and N. Potter, pp. 189–193.</ref> 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&nbsp;°C but is 6 months out of phase with air temperature.<ref name="ReferenceB"/> 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&nbsp;km to the southeast on the southern side of South Mountain near the West Conewago Creek, Lat 40`04'56", long 76`43'13".<ref name="ReferenceB"/>

[[Image:Bsprings2.jpg|thumb|right|The Bubble]]

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 (Pennsylvania)|Boiling Springs High School]] mascot, "The Bubblers", was inspired by this spring.