Composition of the land

The Niagara Parks Power Station sits on a flat parcel of solid bedrock that formed nearly 430 million years ago. The land is composed of many different layers of sedimentary rock, called strata. Here’s a look at the layers of land that were excavated to construct this tunnel.
  • Topsoil (15 ft.): A mixture of decomposed organic matter, gravel and boulder overburden.
  • Guelph (10 ft.): Created when the upper rapids flowed over and cut through the Guelph formation. This layer is composed of a grainy dolomite full of rock cavities lined with mineral crystals such as calcite and gypsum.
  • Eramosa (62 ft.): The Eramosa layer is made up of aphanite, a fine-grained type or rock with mineral crystals undetectable by the naked eye. This pale brown layer is limited to the area closest to the falls.
  • Goat Island (13 ft.): Estimated to be between 419 and 443 million years old based on the fossils found within the layer. The fossilized wormlike marine animals of the Triassic Period are believed to be some of the earliest known in the world. Some of the large rocks at the base of the falls came from this layer.
  • Gasport (29 ft.): This layer started as dense underwater formations called thickets. These thickets consisted of branching corals and algae fields. The limestone and dolomite also found in this layer are the same kind used to construct the power station. Their low absorption and porous properties were ideal for a building surrounded by water.
  • DeCew (6 ft.) The upper surface of the DeCew layer has a varied thickness due to erosion. It is easily identifiable by the rippling curved breaks found in the rock, known as Conchoidal fracturing.
  • Rochester (30+ ft.): Features soft and easily erodible layers of shale formed underwater from mud. The bottom of this layer is supported by folk limestone made of skeletal fossil fragments and calcite cement. Over 200 fossilized species have been identified in the Rochester layer.
  • Medina sandstone: Even after the tunnel reached a depth of 174 feet, workers continued to dig down an additional 35 feet under the tunnel to the Medea Sandstone layer. This was to ensure that the tunnel sat on a more solid base than what the Rochester shale provided.