Editing Bruce Peninsula National Park (section)

==Geology==
[[File:Bruce peninsula national park 4.JPG|200px|left|thumb|"The Grotto" at Bruce Peninsula National Park]]
The [[Niagara Escarpment]] runs from near [[Rochester, New York|Rochester]], New York, to [[Tobermory, Ontario|Tobermory]], then on to [[Manitoulin Island|Manitoulin]], [[St. Joseph Island (Ontario)|St. Joseph Island]] and other islands located in northern [[Lake Huron]] where it turns westwards into the [[Upper Peninsula]] of northern Michigan, south of [[Sault Ste. Marie, Michigan|Sault Ste. Marie]]. The escarpment then extends southwards into [[Wisconsin]] following the [[Door Peninsula]] and then more inland from the western coast of [[Lake Michigan]] and [[Milwaukee]] ending northwest of [[Chicago, Illinois|Chicago]] near the Wisconsin-Illinois border. It forms the backbone of the [[Bruce Peninsula]] and shapes the northern boundary of most of the park and provides the park with some of its most spectacular scenery.

The rock of the escarpment is very old. Approximately 400 million years ago, this area was covered by a shallow tropical sea teeming with life in the form of plant-like animals, [[crustacean]]s, living [[coral]]s and [[mollusk]]s. It would have looked much like the present-day [[Great Barrier Reef]] of [[Australia]]. When the sea began to dry up, the minerals dissolved in it became more and more concentrated. [[Magnesium]] in the water was absorbed into the [[limestone]], which then became a harder, slightly different sort of rock, called [[Dolomite (rock)|dolomite]].

The harder dolomite forms much of the rock of the escarpment cliffs along Bruce Peninsula National Park's Georgian Bay shoreline. At Niagara Falls, the dolomite "caprock" is more resistant to erosion than the rock below it, creating the sculptured cliffs for which the area is famous. Since the [[Last Glacial Period|last ice age]], water levels in the region have undergone great changes. Softer limestone has been eroded away by water action, leaving magnificent overhanging cliffs at various points along the shore. These are the big attraction of the Cyprus Lake trails. Where erosion has cut more deeply, caves have been formed, such as the famed "Grotto" on the shore between the Marr Lake and [[Georgian Bay]] Trails. Great blocks of dolomite, undercut by wave action, have tumbled from the cliffs above and can be clearly seen below the surface of the deep, clean waters of Georgian Bay.