The assumption that slow processes are silent often leads to the question of whether erosion makes a sound. Erosion, the wearing away and transport of Earth materials by natural forces, is a constant source of acoustic energy. The sounds range from the violent, booming thunder of collapsing ice to the nearly inaudible creaking of shifting soil. These noises are a direct byproduct of kinetic energy converting into audible waves, providing scientists with a passive method to measure the rate and force of landscape change.
The Physics: How Erosion Generates Sound
The science of erosion-generated sound relies on the transfer of mechanical energy from moving material into the surrounding medium, whether air, water, or solid ground. Sound waves are mechanical vibrations traveling through matter. The most common mechanism is impact, which occurs when one particle strikes another or a stationary surface. For instance, a single water drop hitting bare soil can generate a sound pressure level between 29 dB and 42 dB, depending on the soil’s particle size distribution.
Another mechanism is friction or abrasion, which involves the grinding and rubbing of materials as they slide past one another. This action releases energy as high-frequency vibrations. When rocks or sediment are dragged across a bedrock riverbed, they produce a distinct acoustic signature.
When materials move in large quantities, they also generate vibration that travels through the earth. The energy from the collision of rocks in a river, known as bedload transport, creates ground vibrations detectable by seismometers, often in the low-frequency range of 10–150 Hz. The river channel or a large glacial mass can resonate from this movement, turning the landscape itself into a noise generator.
Dynamic Sounds of Water and Ice
The most energetic and perceptible sounds of erosion are produced by water and ice, the planet’s most powerful sculpting agents. Coastal wave action on shingle or gravel beaches creates a characteristic, loud clatter as the backwash and uprush move coarse particles, sometimes up to 40 mm in diameter, back and forth. Within rivers, the sound of bedload transport—the rolling and scraping of stones along the bottom—is a continuous, deep rumble that varies with flow intensity. Hydroacoustic sensors monitor this underwater sound, which indicates the erosion rate in the channel.
Glacial erosion, particularly calving, creates a complex acoustic environment. When massive chunks of ice break off a glacier and crash into the sea, they produce distinct rumbles, snaps, and violent splashes. Submarine calving, where ice detaches below the waterline, generates powerful, low-frequency sounds that can travel for thousands of kilometers underwater. These large calving events generate some of the loudest natural underwater sounds in the Arctic Ocean. Additionally, the melting of glacial ice releases tiny pockets of trapped air, producing a steady, high-frequency sound described by scientists as sounding like “bacon frying” or “hissing static.”
The Subtle Noise of Wind and Gravity
Less energetic forms of erosion result in quieter, measurable acoustic phenomena. Wind erosion operates through a process called saltation, where sand particles bounce across the ground surface in short, low trajectories. The noise from this process is a faint hiss or crackle, created by the rapid impacts of millions of sand grains hitting the ground and dislodging other particles. These sounds are often masked by the noise of the wind itself, but they are a constant acoustic signal of surface-level transport.
Gravity-driven mass wasting, such as landslides and rockfalls, generates sudden, loud, broadband noise upon impact, detectable by seismic networks. The energy released by a large rockfall is converted directly into ground vibration and airborne sound. A subtler form of gravity erosion is creep, the gradual, downslope movement of soil and rock over long time scales. This slow shifting is inaudible to the human ear but produces low-level, continuous acoustic signals. Specialized geophones are required to detect these signals, providing researchers with insight into the relentless reshaping of hill slopes.