The earth is active and dynamic. The surface of the earth is the result of a complex balance of all forces acting upon it. Mountains, rivers, forests, continents, and oceans shift and change through time. We as individuals and a species only see the earth through a small window during which the rate of change may not be noticeable, except during dramatic events.

Tectonic forces acting beneath the earth's crust drive regional uplift, earthquakes, and volcanoes. Along parts of California's Pacific margin, the rate of uplift is more than four meters per thousand years. At these rates, portions of the California Coast Ranges and the Transverse Ranges could be twice of more the height of Mt. Everest. Although most active along the Pacific Rim, uplift has affected part of every land mass.

Fortunately for life on earth, landslides counterbalance some of the uplift. The components of gravity, water erosion, wind, and development are some of the causes for landslides. The natural strengths of the earth materials, cohesion (the stickiness of soil) and reinforcement by plant roots help a slope to resist sliding. Landslides occur when the forces driving failure are greater than those resisting movement.

As noted, uplift rates are not the same everywhere. Likewise, earth materials are highly variable and inhomogenous in strength, porosity, and resistance to weathering. Coupled with this, precipitation patterns are chaotic. These factors interact in an elegant, complex fashion, triggering landslides of many types, volumes, and and rates of movement.

A landslide stops when the resisting forces again exceed the driving forces. Once this occurs, new soil develops and surface features soften. With changing conditions, the landslide may again become unstable. Where landslides are a dominant mountain flattening process, portions of a hill may be in any state of recovery. The variations in hill form and soil properties aid in forming the rich diversity of habitats that can be used by many different plant and animal species.

Landslides may also provide diversity in streams. Rocks and soil brought into a stream may fill pools and smother gravel. Conversely, the landslide debris may be washed and sorted, with the gravel retained used for spawning by fish and the fine-grained sediments nourishing riparian floodplains. Similarly, logs and trees brought into stream channel may form blockages to fish migration or generate important habitat structures.

Landslides are neither good nor bad. They are a natural component of all hill slopes and are processes that contribute to the diverse physical habitat of the surface of the earth.