Field-trip guide to a volcanic transect of the Pacific Northwest

Scientific Investigations Report 2017-5022-M
By: , and 



The Pacific Northwest region of the United States provides world-class and historically important examples of a wide variety of volcanic features. This guide is designed to give a broad overview of the region’s diverse volcanism rather than focusing on the results of detailed studies; the reader should consult the reference list for more detailed information on each of the sites, and we have done our best to recognize previous field trip leaders who have written the pioneering guides. This trip derives from one offered as a component of the joint University of Idaho- Washington State University volcanology class taught from 1995 through 2014, and it borrows in theme from the classic field guide of Johnston and Donnelly-Nolan (1981). 

For readers interested in using this field guide as an educational tool, we have included an appendix with supplemental references to resources that provide useful background information on relevant topics, as well as a few suggestions for field-based exercises that could be useful when bringing students to these locations in the future. 

The 4-day trip begins with an examination of lava flow structures of the Columbia River Basalt, enormous lava fields that were emplaced during one of the largest eruptive episodes in Earth’s recent history. On the second day, the trip turns to the High Lava Plains, a bimodal volcanic province that transgressed from southeast to northwest from the Miocene through the Holocene, at the northern margin of the Basin and Range Province. This volcanic field provides excellent examples of welded ignimbrite, silicic lavas and domes, monogenetic basaltic lava fields, and hydrovolcanic features. The third day is devoted to a circumnavigation of Crater Lake, the result of one of the world’s best-documented caldera-forming eruptions. The caldera walls also expose the anatomy of Mount Mazama, a stratovolcano of the Cascade Range. The last day is spent at Newberry Volcano, a back-arc shield volcano topped by a caldera. Newberry is compositionally bimodal with an abundance of explosive and effusive deposits, including the youngest rhyolites in the Pacific Northwest.

Suggested Citation

Geist, Dennis, Wolff, John, and Harpp, Karen, 2017, Field-trip guide to a volcanic transect of the Pacific Northwest: U.S. Geological Survey Scientific Investigations Report 2017–5022–M, 31 p.,

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Preface
  • Contributing Authors
  • Introduction
  • Geologic Background
  • Acknowledgments
  • References Cited
  • Appendix—Supplemental Educational Materials Relevant to Field Trip
Publication type Report
Publication Subtype USGS Numbered Series
Title Field-trip guide to a volcanic transect of the Pacific Northwest
Series title Scientific Investigations Report
Series number 2017-5022
Chapter M
DOI 10.3133/sir20175022M
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Volcano Science Center
Description ix, 31 p.
Country United States
State Oregon
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details