Silty soil is made of fine, powdery sedimentary particles. Construction disasters can be caused by such a thaw and the resulting subsidence, or settling, of surface features. Thermosiphons offered one solution to permafrost on the Alaska pipeline. Other options exist. To avoid settling, engineers try to build on bedrock or coarse, well-drained soil with a low ice content.
Builders can also maintain stable soil by insulating structures to prevent permafrost thawing.
Small, lightweight structures may need only an airspace between floor and soil surface, created by raising the building on stilts. Larger structures require the support of insulated pilings driven deep into the permafrost. This technique allowed the Russians to build entire cities on permafrost in Siberia. Permafrost's capacity to preserve plants and animals for centuries gives scientists a window into the past to help them assess how rapidly greenhouse pollutants may be warming the Earth. Ground temperatures indicate past climatic conditions and current changes in world ambient temperatures, providing an understanding of the complex interactions of human-induced global warming, ice melting, and potential sea level changes.