How Much Basalt Is Below Lake Superior

Lake Superior is located in the Midwest United States, roughly on the border of Minnesota and Wisconsin and Ontario, Canada. It is the largest of the five Great Lakes, famously referred to as “Gitche Gummi” by the indigenous Ojibwe people. A significant feature of this lake is that it is largely composed of basalt, a type of volcanic rock.

Basalt is a “dark-colored, fine-grained, igneous rock composed mainly of plagioclase, pyroxene, and some olivine. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill.” So, how much basalt is actually underneath the lake?

Scientists suggest that Lake Superior is composed of roughly 16.4% basalt. This is a significant amount considering that basalt, in comparison to other rock types, is quite rare and hard to find. According to a study from the University of Minnesota Duluth, between 1.3 to 5.3 billion cubic meters of basalt, is below Lake Superior.

What makes this phenomenon so interesting is that it is a result of billions of years of volcanic activity. This is because “basaltic basement rocks, which are the oldest rocks of our continent, were the original material that made the ancient North American bedrock”. In the present day, the basalt found in this lake originates from the Midcontinent Rift System, which is a 2.7 billion year old system of dikes and faults.

The MRCS covers an area of more than 250,000 square kilometers and extends from the Great Lakes all the way to Lake Winnipeg in Canada. The Lake Superior basin is situated right in the middle of this large area, allowing it to be heavily saturated with basaltic rock. Other geological components of this lake are, limestone, sandstone, and shale.

Environmental Impacts

The high quantity of basalt under the lake may have had an environmental impact. This is especially true considering that basalt is known to absorb nutrients and water more readily than other types of rock. This allows for Lake Superior to form a more diverse ecology system as it can contain more marine species.

Additionally, basalt is known to grow macrophytes and algae, which are both essential to sustaining life in the water. Furthermore, the mere presence of basalt in the lake could have acted as a protective barrier. As basalt is a tough, durable rock, it may help to protect the lake from the elements. It is also used to filter the water, keeping it at the optimal pH levels for aquatic life to thrive.

Benefits for Human Beings

The basalt beneath Lake Superior also has a wide range of benefits for humans. For starters, it is a great source of minerals. This has attracted miners to the area in search of copper, silver and gold. Additionally, basalt is known to contain silicates, which are used to make mortar and cement. These materials are in turn used to construct and build homes.

Other items made with basalt may be found in our everyday lives, such as asphalt, which is a material commonly used in road construction. Basalt is also used in landscaping and construction projects, something that can be seen on the shores of Lake Superior. Furthermore, basalt fabric is used in architecture to make countertops, tiles and even sculptures. Its thermal stability and “high resistance” make it an ideal material for human applications.

Population Changes

The presence of basalt in Lake Superior may have also had an impact on its population levels. It is possible that the presence of basalt in this lake gave the area an evolutionary advantage. Its ability to filter out water and its resistance to elements, may have allowed certain organisms to thrive in this environment. Consequently, these organisms may have played an important role in the development of the area’s ecology. Furthermore, these organisms may have also helped to support the area’s population growth.

In addition, the presence of basalt in Lake Superior could have also supported the local economy. The valuable minerals underneath the lake may have attracted people to the area, in the hopes of extracting these commodities. Furthermore, locals may have traded in these items. Therefore, it is arguable that the basalt in Lake Superior played an important role in the area’s development.

Effects on Water Quality

The presence of basalt underneath Lake Superior may have also had a positive effect on the lake’s water quality. Basalt’s water retention and filtration capabilities, may have prevented erosion and the build-up of toxins in the lake. This is because basalt can act as a natural filter, removing potential pollutants from the water.

Basalt is also known for its ability to absorb toxins; something that may be an important factor in preserving the lake’s water quality. Furthermore, basalt’s durability also prevents it from eroding. This may have had a significant impact in preventing against water pollution as it may have decreased the amount of sediments that get into the lake. Thus, basalt may have had a direct effect in preserving the lake’s environment.


It is evident that the basalt underneath Lake Superior has had a substantial influence on the area. It has provided the lake with a unique environment, contributing to its evolution, adaptation, and achievements. It has also provided with a great source of valuable minerals, which have been extracted for human use. Additionally, the presence of basalt has been instrumental in maintaining the water quality in the lake. It is clear that this type of rock has been vitally important in the evolution of Lake Superior and its presence is far from insignificant.

Todd Hashimoto is a nature writer and enthusiast. He has a special interest in ecotourism, particularly for lakes around the world. He has traveled extensively for his research, visiting some of the most renowned bodies of water on every continent. His writing covers topics like lake ecology and conservation as well as interesting historical and cultural facts about famous lakes. He is passionate about bringing attention to the beauty and importance of these natural wonders in hopes of promoting their protection.

Leave a Comment