Editing Biscayne National Park (section)

==Geography==
[[File:Biscayne National Park Map 2009.png|thumb|alt=Park map|Map of Biscayne National Park<ref>{{Webarchive|url=https://web.archive.org/web/20130115150822/http://hfc.nps.gov/carto/PDF/BISCmap1.pdf |date=2013-01-15 }}</ref>]]
Biscayne National Park comprises {{convert|172971|acre|sqmi km2|1}} in [[Miami-Dade County]] in southeast Florida.<ref name=area/> Extending from just south of [[Key Biscayne]] southward to just north of [[Key Largo]], the park includes [[Soldier Key]], the [[Ragged Keys]], [[Sands Key]], [[Elliott Key]], [[Totten Key]] and [[Old Rhodes Key]], as well as smaller islands that form the northernmost extension of the [[Florida Keys]]. The [[Biscayne Bay#Safety Valve|Safety Valve]], a wide shallow opening in the island chain, between the Ragged Keys and Key Biscayne just north of the park's boundary, allows [[storm surge]] water to flow out of the bay after the passage of tropical storms. The park's eastern boundary is the ten-fathom line ({{convert|60|ft|m|adj=on|disp=semicolon}}) of water depth in the Atlantic Ocean on the [[Florida Reef]]. The park's western boundary is a fringe of property on the mainland, extending a few hundred meters inland between [[Cutler Ridge]] and Mangrove Point. The only direct mainland access to the park is at the Convoy Point Visitor Center, adjacent to the park headquarters.<ref name=bischrs1>{{cite web|last=Leynes|first=Jennifer Brown|title=Introduction|url=http://www.nps.gov/parkhistory/online_books/bisc/hrs/chapter1.pdf|work=Biscayne National Park Historic Resource Study|publisher=National Park Service|access-date=28 November 2012|author2=Cullison, David|page=1|date=January 1998}}</ref>  The southwestern boundary adjoins the [[Turkey Point Nuclear Generating Station]] and its system of cooling canals.<ref name=biscbrochure1>{{cite book|title=Biscayne National Park Brochure and Map|year=2009|publisher=National Park Service}}</ref>

The southern portion of [[Biscayne Bay]] extends between Elliott Key and the mainland, transited by the [[Intracoastal Waterway]]. The park abuts the [[Florida Keys National Marine Sanctuary]] on the east and south sides of the park and [[John Pennekamp Coral Reef State Park]] to the south.<ref name=biscbrochure1/> Only {{convert|9075|acre|abbr=on}} of the park's area are on land, with the offshore keys comprising {{convert|4250|acre|abbr=on}} and mainland mangrove swamps account for the remaining {{convert|4825|acre|abbr=on}}.<ref name=bischrs1/> As an extension of the Everglades ecosystem, much of the park was originally proposed to be included in [[Everglades National Park]], but was excluded to obtain a consensus for the establishment of the Everglades park in 1947.<ref name=grunwald1>Grunwald, p. 214</ref>

===Geology===
[[File:Biscayne underwater NPS1.jpg|thumb|alt=Sunlight on an underwater coral reef|Underwater view of a [[coral reef]] at Biscayne National Park]]
[[Biscayne Bay]] marks the southernmost extent of the Atlantic barrier islands, represented by [[Key Biscayne, Florida|Key Biscayne]] and the northernmost extent of the [[Florida Keys]] at [[Elliott Key]]. The keys are distinguished from the barrier islands by the coral limestone that extends to the islands' surface under a thin veneer of topsoil, while the barrier islands are dominated by wave-deposited sands that cover most of the limestones.<ref name=bryan1>Bryan ''et al.'', p. 288</ref> Biscayne Bay lies between low ridges of [[Oolite|oolitic]] Miami Limestone on the west, forming [[Cutler Bay, Florida|Cutler Ridge]] and the coral-based Key Largo limestone that underlies Elliott Key and the keys to the south. The Miami limestone was deposited in turbulent lagoon waters.

The Key Largo Limestone is a fossilized coral reef formed during the [[Sangamonian]] Stage of about 75,000 to 125,000&nbsp;years ago. The Miami Formation achieved its present form somewhat later, during a glacial period in which fresh water consolidated and cemented the lagoon deposits.<ref>Bryan ''et al.'', pp. 287–290</ref> The Key Largo Limestone is a coarse stone formed from stony corals, between {{convert|69|and|200|ft|abbr=on}} in thickness.<ref>Bryan ''et al.'', p. 298</ref> As a consequence of their origins as reefs, the beaches of Elliott Key and Old Rhodes Key are rocky. Significant sandy beaches are found only at Sands Key.<ref name=bnmecology>{{cite web|title=The Ecology|work=Biscayne National Monument: A Proposal|url=http://www.nps.gov/parkhistory/online_books/bisc/proposal/sec4.htm|publisher=National Park Service|access-date=7 January 2013}}</ref>

===Hydrology===
Biscayne Bay is a shallow semi-enclosed lagoon which averages {{convert|10|ft|abbr=on}} in depth.<ref name=wbiscsalin8>{{cite web|title=Estimates of Flows to Meet Salinity Targets for Western Biscayne National Park|url=http://digitalcollections.fiu.edu/sfrc/pdfs/FI11060804.pdf|publisher=National Park Service|access-date=8 January 2013|page=8|date=June 2008|url-status=dead|archive-url=https://web.archive.org/web/20130521210355/http://digitalcollections.fiu.edu/sfrc/pdfs/FI11060804.pdf|archive-date=21 May 2013}}</ref>  Both its mainland margins and the keys are covered by mangrove forest. The park includes the southern portion of Biscayne Bay, with areas of thin sediment called "hardbottom", and vegetated [[seagrass meadow]]s supporting turtlegrass and shoal grass.<ref name=npsbisc1>{{cite web|title=Biscayne Bay|url=http://www.nps.gov/bisc/naturescience/biscaynebay.htm|work=Biscayne National Park|publisher=National Park Service|access-date=19 November 2012}}</ref>

As a result of efforts to control water resources in Florida and projects to drain the [[Everglades]] during the early and mid-20th century, water flow into Biscayne Bay has been altered by the construction of canals. These canals channel water from portions of the southeastern Everglades now used for agriculture into the bay. Prior to canal construction, most fresh water inflow came from rain and groundwater, but the canals are now altering the salinity profile of the bay, conveying sediment and pollutants and leading to [[saltwater intrusion]] into the Biscayne aquifer. The [[Comprehensive Everglades Restoration Plan]] (CERP) was established in 2000 to mitigate the effects of human intervention into the natural water flow of the Everglades. Primarily aimed at the [[Restoration of the Everglades|restoration of historical patterns of water flow]] into Everglades National Park, the project will also deal with issues arising from the diversion of water out of the southern Everglades into Biscayne Bay.<ref name=sotpbisc2>NPCA, p. 2</ref> The Biscayne Bay Coastal Wetlands Project (BBCW) is a CERP component specifically intended to redistribute water flow so that fresh water is introduced gradually through creeks and marshes rather than short, heavy discharges through drainage canals.<ref name=npca13>NPCA, p. 13</ref>