On the north shore of Lake Superior, between Marathon and Terrace Bay, Ontario, lies Neys Provincial Park. It is a beautiful park, home to some very stunning geological features. The most interesting of which is the Coldwell Complex. The Coldwell Complex is the remnants of an ancient volcano that erupted over a billion years ago.


The Coldwell Complex first began to form over 1.1 billion years ago. Back then the northern shoreline of Lake Superior was part of a continental rift zone, where the earth’s crust was splitting apart due to the movement of the tectonic plates. As this occurred, Magma started to rise up through the cracks and holes in the crust. Eventually, the magma began to swell up onto the Earth’s surface. Over time the magma accumulated in such a large amount that it began to form a volcano. The volcano erupted periodically for millions of years, being continuously fed from the magma below.
Approximately 600 million years ago the volcanic activity finally ceased, and the volcano walls became so large and heavy that they collapsed inward, forming a large depression in the Earth, known as a caldera. The magma chamber became sealed by the fallen rocks. The magma slowly cooled and crystallized over time, forming different Igneous (magmatic) rocks with various minerals and textures.



During the last ice age, about 66 million years ago, glaciers covered most of North America. As the glaciers moved and melted, they caused erosion on the Earth’s surface, which began to expose the top layers of the Coldwell Complex. The result of this was that the ancient magma chamber and its diverse rock formations became visible on the surface.
The Coldwell Complex stretches 25 kilometres in diameter, 30% of which lies beneath Lake Superior.
Long parallel scratches on the rocks’ surfaces, known as glacial striations can also be seen. This is the result of the retreating glaciers dragging stones across the volcanic rock.



The volcanic remains in Neys Provincial Park are incredibly unique and do a fantastic job of revealing the ancient history of the earth. The history here, which stretches back over a billion years, is displayed in such a way that every individual, regardless of their scientific knowledge, can enjoy and understand it. The scientific, historical and aesthetic beauty of this area makes it an excellent destination for camping, hiking and learning.