Most of Lambton County is covered by a large, relatively level clay plain. The Lake Huron shoreline and the northeastern part of the County exhibit evidence of ancient glacial lakes: sand deposits, beach terraces, shorecliffs, and moraines. Close proximity to Lake Huron, the St. Clair River, and the northern edge of the Carolinian Forest zone, give the area a high amount of biological diversity.

The soil in this region is a very important natural resource as it is within the main agricultural region of the province. The soil is very rich and productive owing its existence to the ancient sea that once flooded this area for a long period of time. During this time, organisms and plants fell into the sea leaving multiple layers of sediment behind. This sea floor also created very flat land making it ideal for agriculture. The subsequent deposits of decaying organic material also has endowed the area with rich oil deposits.