Unconformities: Geologic Evidence of Time and Process. An unconformity exists between two rock layers when which geologic processes has occurred?

Unconformities: Geologic Evidence of Time and Process

An unconformity is an interface between two rock layers where a period of erosion or non-deposition has occurred. It is an interruption in the rock record, and geologists use unconformities to help understand the geologic processes that have occurred over time. In order to identify an unconformity, geologists examine the characteristics of the rock layers, looking for angular discordance, erosional surfaces, or change in lithology (Vance, 2019). Angular discordance occurs when two rock layers are not parallel, indicating that one layer has been tilted or eroded prior to the other layer being deposited. Erosional surfaces are flat surfaces that have been created by erosion, and a change in lithology is a difference in the physical characteristics of two adjacent rock layers, such as a change in grain size or composition (Leeder, 2018). The presence of an unconformity is evidence that a period of time has been omitted in the rock record. This specific period of time is referred to as the unconformity gap, and the events that occurred during this gap can be classified as either diastrophic or epeirogenic… Cont…