Shield greenstone north
Rocks in this area form from magma that formed by melting in the Earth's mantle. The magma was erupted onto the Earth's surface as lava and solidified to form basalt, a dark coloured igneous rock rich in iron and magnesium. Some of these rocks have been altered by heat and reaction with water, to form greenstone. They represent part of the Canadian Shield, one of the oldest parts of the Earth's crust.