bushes and herbaceous plants such as grasses and sedges are typical of the alvar plant community. This delicate ecosystem manages to eke out a living under extreme and fluctuating conditions of temperature, moisture and poor soils.
When you visit you will see a great deal of almost flat-lying, smooth pavement, linked to the movements of the glaciers. Soils are thin or almost non-existent. Because of the softness, the pavements cracks form and become increasingly dissected. These collect soil and plants take root. The sparsely vegetated bedrock barrens that develop are in fact the alvars.
I contacted one of the three authors of ‘Manitoulin Rocks!’.
Peter Russell is the Curator for the Earth Sciences Museum at the University of Waterloo. Their aim was to present a ’simplified account‘ of the geological history and to present interesting and unusual facts. It is a guide book you will want to have before visiting.
And Peter knows his rocks. The ‘Peter Russell Rock Garden,’ named in his honour is the best outdoor space on campus. While originally created to commemorate the 25th anniversary of the University of Waterloo in 1982, this educational and beautiful university landmark located in the heart of campus has grown steadily over the years to contain over 70 large specimens of rocks and minerals.
Of particular interest on the island are the clints and grikes. Due to the solubility of limestone, found everywhere on Manitoulin, limestone pavements are associated with some very curious and unusual landforms. The most characteristic surface feature of limestone pavements is their division into blocks, called clints, bounded by deep vertical fissures known as grikes.
Water dissolves the stone, enlarging joints and bedding planes. On the surface, the chemical weathering widens and deepens cracks to form grikes. This leaves exposed blocks of limestone. called clints, and the resulting pattern of blocky rock is called a limestone pavement. A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial pavement. The term is mainly used in the United Kingdom where many of these landforms have developed distinctive surface patterning resembling paving blocks.
Alvars are ecologically different and only on Manitoulin can you see clints and grykes.