The Formation of the Niagara Escarpment

The rocks layers of the Niagara Escarpment are a fossil record of nearly 30 million years of evolution dating from the upper Ordovician (445 million year ago) to the lower Silurian era (420 million years ago) in the Paleozoic Era; a period of 25 million years. The rock below, and east of the escarpment is mostly Ordovician limestone. The rock on, and west of the escarpment is mostly Silurian dolostone. Because of this, the escarpment was once called the Silurian Escarpment.

But how did that happen?

The Lower layer of Escarpment Rock

Approximately 450 million years ago, the area was covered with a warm water sea covering a depression in the earth called the Michigan Basin which had the earliest forms of life living on the muddy bottom. As these early creatures died, their bodies settled to the bottom of the sea. Dirt and mud and sand we call “sediment” would be washed into the sea and cover the remains of these creatures. As it compressed, mud and silt would form layers of shale; sand into sandstone; and corals, calcium-rich exoskeletons and lime mud into limestone. The remains of the many species of sea creatures became fossils, There were trilobites, crinoids (animals which look like plants), shellfish and corals within the layers of sediment.

The Cap Rock is the Coral

The upper, newer, harder layers contain fossils of more complex and diverse life. A chemical reaction between the limestone of the reefs and shells, and magnesium-rich groundwater over a long period of time created a hard, resistant layer known as dolostone rock. Two hundred and fifty million years ago at the time of the dinosaur, the Michigan sea disappeared for the last time, and a long period of erosion began exposing the rock. The receding glacier 12,000 years ago and constant erosion formed it into what it is today.

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