Chapter 15 - Normal Fault-Dominated Landscapes

Abstract

Active and recently active normal faults form perhaps the most conspicuous and widespread landscapes in the Cordillera. Not only are they ubiquitous across the Basin and Range physiographic province, they have infiltrated nearly every province in the Cordillera. This chapter describes normal fault-dominated landscapes, which include the Basin and Range, the Rio Grande Rift, and the Triassic Lowlands. Normal faults form via extension and result in an increase in land area. Basin and Range extension in Nevada and Utah began primarily after about 17 million years ago, intensified less than 10 million years ago, and has completely reincarnated the landscape. Two of the best-known and best-studied normal fault mountain ranges are the Teton Mountains and the Wasatch Range. Both formed primarily within the past 10 million years and both are active. The Rio Grande Rift is an extension of the Basin and Range northward into the Southern Rockies. It too is active. The Triassic Lowlands represent an ancient normal fault landscape within the Appalachian Mountains.