Lake Superior, the largest and deepest of the Great Lakes, is a unique body of freshwater known for its vast size and frigid temperatures. Decomposition does occur in its depths, but the lake’s specific environmental conditions dramatically reduce the rate and alter the process compared to warmer, shallower bodies of water. This extreme slowdown of natural decay has led to the lake’s reputation for preserving remains, raising the question of what specific factors cause this phenomenon.
Standard Biological Decomposition
Decomposition in a typical environment, such as on land or in warm water, is a rapid, multistage biological and chemical process. The initial stage is autolysis, where the body’s own enzymes begin to break down cells and tissues shortly after death. This self-digestion prepares the remains for the next, more dramatic phase of decay.
The putrefaction stage is driven primarily by the gut microbiome, particularly anaerobic bacteria like Clostridium species, which proliferate after oxygen is depleted. These microbes consume tissue proteins and carbohydrates, releasing foul-smelling gases such as methane and hydrogen sulfide. This gas production causes significant bloating, which is the mechanism that typically causes a body submerged in warmer water to float to the surface.
Temperature is the primary regulator for the speed of these processes, with optimal bacterial and enzymatic activity occurring between 21 and 45 degrees Celsius. Warmer conditions accelerate autolysis and putrefaction, leading to rapid decay, whereas cold temperatures significantly slow down the metabolic rates of the bacteria. Without the necessary heat, the chemical reactions required for swift decomposition cannot proceed efficiently.
Environmental Conditions that Slow Decay
The physical attributes of Lake Superior create an environment hostile to the normal process of putrefaction. The lake’s vast volume acts as a thermal sink, maintaining water temperatures in the deepest sections at a near-constant 4 degrees Celsius (39 degrees Fahrenheit). This extreme cold is the most significant factor in preservation, as it dramatically inhibits the growth and enzymatic activity of the putrefactive bacteria.
Because the bacteria that cause bloating and gas production are largely inactive in this cold, the remains often remain dense and sink to the bottom instead of floating back to the surface. Furthermore, the deep trenches of the lake often feature low-oxygen, or anaerobic, conditions. This lack of dissolved oxygen at depth restricts the activity of aerobic bacteria, which are the main drivers of rapid decay and the associated putrefactive changes.
The water itself is also oligotrophic, meaning it is low in nutrients, which further suppresses the overall microbial and biological activity. High hydrostatic pressure in the deepest areas, which can exceed 400 pounds per square inch, also plays a minor role by physically compacting tissues.
Adipocere: The Mechanism of Preservation
When remains are subjected to the specific conditions of Lake Superior—cold, wet, and anaerobic—normal decay is often replaced by a chemical process called saponification. This process converts the body’s fatty tissues into a waxy, soap-like substance known as adipocere, or “grave wax.” The transformation occurs when the lipids, or fats, are hydrolyzed and then hydrogenated by the action of anaerobic bacteria in the absence of oxygen.
Adipocere formation effectively halts the putrefactive decay of soft tissues and can begin to appear within a few months. Once formed, this durable, whitish material encases and preserves the body’s form, acting as a natural, long-term mold. This mechanism is the reason remains recovered from the lake, sometimes decades later, can appear surprisingly intact and recognizable.
Scavenging, Light, and Retrieval
The deep environment of Lake Superior also lacks many of the external factors that accelerate tissue breakdown in other bodies of water. The depth prevents light penetration, creating a dark, cold environment where large aquatic scavengers, such as fish and crustaceans, are scarce or inactive. This absence of predation means the remains are not physically disturbed or scattered.
The practical difficulties of retrieval are compounded by both the immense depth and the lack of a gas-induced bloat stage. Since the bodies rarely resurface, they remain on the lakebed, often settling in deep trenches or within the confines of a shipwreck. Locating remains in the lake’s nearly 1,300-foot maximum depth is a significant challenge, making recovery rare.