terrace

With almost carpenterlike precision, using water as a favorite tool, nature frequently carves from sloping terrain the benchlike surfaces known as terraces. A lake terrace commonly occurs at the water’s edge but may sometimes be well above it, marking the height of an earlier lake level. In glacial terrain, wave action along a lake coast frequently creates a steep-fronted breaker terrace of heavy cobbles that will remain intact during severe storms that destroy associated breaker terraces composed of lighter gravels, built up by previous storms. Marine terraces are found at the seaward edge of the land, gently sloping terrains of water-sorted geological debris eroded from sea cliffs and often uplifted by tectonic forces. Hanging bog is a term often used to designate a water-saturated terrace located partway up the lower slopes of wooded hillsides. A river terrace might be part of a former floodplain, a nearly level area of sand, clay, gravel, and silt left behind when a river excavated its bed through wet and dry climatic periods. Terrace flights are the most dramatic examples of river terracing, a series of platforms that resemble stairs and which are created by the looping meanders of a stream steadily cutting its bed. The flow of mineral-rich waters at a hot springs, on the other hand, builds up terraces of opal-like travertine, bringing an angular beauty to the landscape. Arresting examples occur at Thermopolis, Wyoming, and along Havasu Creek in Arizona.

Mike Tidwell