Author Question: Describe the history of the Pleistocene ice ages. What will be an ideal ... (Read 61 times)

wenmo · **on:** Jul 15, 2018

Describe the history of the Pleistocene ice ages. What will be an ideal response?

Question 2

Briefly describe the geologic history of the North American Cordillera. What will be an ideal response?

samiel-sayed · **Reply #1 on:** Jul 15, 2018

Answer to Question 1

The Pleistocene began 1.6 million years ago and ended 10,000 year ago, during which several intervals
of continental glaciation and warmer interglacial periods took place. There were 20 major warm-cold
cycles during the last 2 million years. The four major Pleistocene glacial episodes were named for the
states in which the most southerly glacial deposits are well exposed: the Nebraskan, Kansan, Illinoian,
and Wisconsinian.

Answer to Question 2

The history of the Cordillera is long and complex, involving accretion of island arcs along the
continental margin, orogeny at an oceanic-continental boundary, vast outpourings of basaltic lava, and
block faulting. After cessation of the Laramide orogeny, mountain ranges eroded. During the Early
Cenozoic, a subduction zone stretched off the Pacific Coast from Mexico to Alaska where the Farallon
plate was consumed. All that remains are the Juan de Fuca and Cocos plates.