Pasadena orogeny

Pasadena orogeny is a mountain building event in the Western United States. Conventionally it refers to the formation of mountains in mainly Southern California during the Pleistocene and lasting until the present day; originally it referred to the uplift of the San Gabriel Mountains.

Geography of Southern California

The Pasadena orogeny is a major Late Quaternary[1]-modern event[2] of mountain formation,[1] which took place in the middle or perhaps late Pleistocene[3] or to the present-day.[4] It is also known as the "Coast Ranges orogeny"[3] or considered to be part of the Cascadian orogeny[5] or Alpide Orogeny.[6] Finally, the term "Pasadena orogeny" is sometimes applied to all very recent orogenies around the Pacific Ocean.[7] The type location is close to Pasadena, California in the Transverse Ranges,[8] and originally referred to the fast rise of the San Gabriel Mountains recorded there.[9]

During this orogeny mountain ranges such as the San Bernardino Mountains, San Gabriel Mountains, San Jacinto Mountains, Santa Monica Mountains, Santa Ynez Mountains[10] and the Transverse Ranges grew,[11] as did the northern Channel Islands[10] such as Catalina Island and San Clemente Island,[12] the Kettleman Hills anticline in the San Joaquin Valley[13] and the Palos Verdes Hills.[14][12] Sometimes the concept is limited to the uplift of the Transverse Ranges.[15]

The general uplift of mountains over a length of over 400 kilometres (250 mi) is caused by the collision of the North American Plate with other geologic structures that are attached to the Pacific Plate.[10] This orogeny has resulted in the uplift of mostly north-south trending mountain chains, although some east-west trending uplifts are also found such as the Channel Islands and the Transverse Ranges;[13] much of the uplift took place at the edge of basins.[16] The Pasadena orogeny is accompanied by earthquake activity, which includes tsunami hazards.[17]

Folding accompanying the uplift of the Coast Ranges in Southern California,[3] folding farther north at Morro Bay[18] and the structure of the Santa Barbara Basin[1] and Ventura Basin are consequences of the Pasadena orogeny.[4] The city of Long Beach, California lies within the affected region.[2]