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* sinkholes may also be caused by a drainage of water, such as a water table decline | * sinkholes may also be caused by a drainage of water, such as a water table decline | ||
* sinkholes are most common where limestone, sandstone, salt beds, or gypsum are prevalent | * sinkholes are most common where limestone, sandstone, salt beds, or gypsum are prevalent | ||
[[File:Thor's Well (37588682016).jpg| | [[File:Thor's Well (37588682016).jpg|250px|border|right|thumb|Thor's Well: a sinkhole on the coast of Cape Perpetua, Oregon]] | ||
* Thor's Well: a sinkhole on the coast of Cape Perpetua, Oregon, that drains at high tides | * Thor's Well: a sinkhole on the coast of Cape Perpetua, Oregon, that drains at high tides | ||
[[File:December_Giant_sinkhole_collapse_USGS_1972.jpg| | [[File:December_Giant_sinkhole_collapse_USGS_1972.jpg|250px|border||right|thumb|More than three acres of forest suddenly disappeared into this "December Giant" sinkhole in Montevallo, Alabama, USA.]] | ||
* Golly Hole in Shelby County is considered the largest sinkhole in the US. | * Golly Hole in Shelby County is considered the largest sinkhole in the US. | ||
** it is 325 ft long, 300 ft wide, and 120 ft deep | ** it is 325 ft long, 300 ft wide, and 120 ft deep | ||
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=== Directional extremes (north, south, east, west) === | === Directional extremes (north, south, east, west) === | ||
'''United States''' | '''United States''' | ||
[[File:USA-Extreme-Points.svg|USA-Extreme-Points|right| | [[File:USA-Extreme-Points.svg|USA-Extreme-Points|right|200px|thumb|Extreme points in the contiguous 48 states: Northwest Angle (MN), Ballast Key (FL), Sail Rock (ME), Bodelteh Islands (WA) See https://en.wikipedia.org/wiki/List_of_extreme_points_of_the_United_States]] | ||
* northernmost state in the continental U.S.: '''Minnesota''' | * northernmost state in the continental U.S.: '''Minnesota''' | ||
* northernmost point in the continental U.S.: '''Northwest Angle''', Minnesota, known as "The Angle" | * northernmost point in the continental U.S.: '''Northwest Angle''', Minnesota, known as "The Angle" | ||
* Click EXPAND to read more about the Northwest Angle: | * Click EXPAND to read more about the Northwest Angle: | ||
<div class="mw-collapsible mw-collapsed | <div class="mw-collapsible mw-collapsed"> | ||
** when negotiating the US-Canadian border following the American Revolution (Treaty of Paris, 1783), negotiators used an inaccurate map of the border of present-day Minnesota and Canada, and thereby included the northwest portion of the Lake of the Woods as the border, while it actually lies within Canadian territory | ** when negotiating the US-Canadian border following the American Revolution (Treaty of Paris, 1783), negotiators used an inaccurate map of the border of present-day Minnesota and Canada, and thereby included the northwest portion of the Lake of the Woods as the border, while it actually lies within Canadian territory | ||
** thus The Angle is one of six "practical exclaves" of the U.S., as it is only accessible by land via Canada | ** thus The Angle is one of six "practical exclaves" of the U.S., as it is only accessible by land via Canada |