 |
|
 |
 |
||||||||||||||
Along the edge of the Niagara escarpment, a dense band of white cedar trees in combination with the limestone bedrock create unique, reduced light conditions for the understory environment. Additionally, the rock faces and crevices, and the slumping bedrock create habitats for a variety of animals making this a unique area of the Arboretum.
What is the Niagara Escarpment?
The Niagara Escarpment is the edge of a thick series of dolomite layers of Silurian age that extends from Ontario Canada into Wisconsin. The dolomite started in shallow seas as tiny aquatic organisms called foraminifera died and their calcium-carbonate shells piled up forming sediment over 400 million years ago. Over time the calcium carbonate was converted to limestone or dolomite. Earlier and later, the sediment was mostly clay, and softer shales built up forming layers of soft over hard rock. The term "Niagara Escarpment" is sometimes used in Iowa, where the same Silurian rocks are exposed and form bluffs.
The Niagara Escarpment is a gently-sloping layer
of rock that forms a ridge or a cuesta. One side of a cuesta is a steep
escarpment of erosion resistant rock, while the other is has a longer
gentle slope of more easily eroded rock. The Niagara Escarpment forms
sharp bluffs along the edge of Green Bay as it extends through Door County.
The escarpment forms because there are layers of hard rocks on top of
soft rocks and the layers are tilted slightly, so the layers are exposed
at the surface at an angle. The tops of the bluffs are mainly composed
of layers of hard Silurian dolomite. Softer layers of Devonian and Ordivician
rock composed of slates and other sedimentary rocks erode away under the
bluff and on the sloping side to create the characteristic cuesta landform.
If water undercuts the bluffs, erosion happens even faster. Eventually
the undercutting is severe enough that blocks of dolomite tumble down
the escarpment forming piles of boulders.
Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects
© 2001-2004 The Cofrin Center
for Biodiversity and the University of Wisconsin Green Bay,
All Rights Reserved
Last
updated on
January 12, 2006