Nipissing sills facts for kids
The Nipissing sills, also known as the Nipissing diabase, are a group of very old, flat rock formations found in Ontario, Canada. These sills formed between 2217 and 2210 million years ago. They are located within the Superior craton, which is a very ancient and stable part of the Earth's crust in the Canadian Shield.
These sills are basically sheets of cooled molten rock that pushed their way into older rock layers. They cut through the Huronian Supergroup, which is a very old collection of sedimentary rocks.
What are Nipissing Sills?
Nipissing sills are a type of sill, which is a flat, sheet-like body of igneous rock. This means they formed when molten rock, called magma, squeezed into cracks between existing layers of rock and then cooled and hardened.
These sills are made of a strong, dark rock called gabbro. They are found in many places, especially around the Sudbury and Elliot Lake areas. In these regions, the Nipissing sills have been bent and changed shape over millions of years. This happened after the older Huronian rocks were already cracked and folded.
Where Did They Come From?
Scientists believe the molten rock that formed the Nipissing sills came from deep inside the Earth. It didn't come from directly beneath where the sills are now. Instead, it traveled a very long distance!
The magma is thought to have come from a huge volcanic event called the Ungava magmatic event. This event happened around the same time, 2217 to 2210 million years ago. It was located far to the northeast, under what is now the Labrador Trough.
The molten rock traveled about 1500 kilometers (930 miles) from this distant source. It moved through long cracks in the Earth's crust, like underground rivers of magma. These cracks are called dikes. One important group of these dikes is the Senneterre dikes, which formed about 2216 million years ago. They helped feed the magma to where the Nipissing sills are found today.
