Time scale
Numbers on the time scale represent time in millions of years before present. Numerical dates were added long after the time scale was established using […]
Nonconformity
Basic types of contacts To understand the concept of nonconformity in the rock formation, it is important to mention the basic types of contacts between […]
Disconformity
A disconformity is a gap in the rock A disconformity is a gap in the rock record that represents a period of erosion rather than […]
Coquina and Chalk
Although a great deal of limestone is produced by biological processes, this origin is not always evident because shells and skeletons may undergo considerable change […]
How Does Shale Form?
Much of what can be learned about the process that forms shale is related to particle size. The tiny grains in shale indicate that deposition […]
The Soil Profile
Because soil-forming processes operate from the surface downward, soil composition, texture, structure, and color gradually evolve differently at varying depths. These vertical differences, which usually […]
Igneous Processes
Igneous rocks Igneous rocks form in two basic settings. Molten rock may crystallize within Earth’s crust over a range of depths, or it may solidify […]