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Emplacement of Holocene silicic lava flows and domes at Newberry, South Sister, and Medicine Lake volcanoes, California and Oregon

Scientific Investigations Report 2017-5022-I
By:  and 
https://doi.org/10.3133/sir20175022I

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Abstract

This field guide for the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly 2017 focuses on Holocene glassy silicic lava flows and domes on three volcanoes in the Cascade Range in Oregon and California: Newberry, South Sister, and Medicine Lake volcanoes. Although obsidian-rich lava flows have been of interest to geologists, archaeologists, pumice miners, and rock hounds for more than a century, many of their emplacement characteristics had not been scientifically observed until two very recent eruptions in Chile. Even with the new observations, several eruptive processes discussed in this field trip guide can only be inferred from their final products. This makes for lively debates at outcrops, just as there have been in the literature for the past 30 years.

Of the three volcanoes discussed in this field guide, one (South Sister) lies along the main axis defined by major peaks of the Cascade Range, whereas the other two lie in extensional tectonic settings east of the axis. These two tectonic environments influence volcano morphology and the magmatic and volcanic processes that form silicic lava flows and domes. The geomorphic and textural features of glass-rich extrusions provide many clues about their emplacement and the magma bodies that fed them.

The scope of this field guide does not include a full geologic history or comprehensive explanation of hazards associated with a particular volcano or volcanic field. The geochemistry, petrology, tectonics, and eruption history of Newberry, South Sister, and Medicine Lake volcanic centers have been extensively studied and are discussed on other field excursions. Instead, we seek to explore the structural, textural, and geochemical evolution of well-preserved individual lava flows—the goal is to understand the geologic processes, rather than the development, of a specific volcano.

Suggested Citation

Fink, J.H., and Anderson, S.W., 2017, Emplacement of Holocene silicic lava flows and domes at Newberry, South Sister, and Medicine Lake volcanoes, California and Oregon: U.S. Geological Survey Scientific Investigations Report 2017–5022–I, 41 p., https://doi.org/10.3133/sir20175022I.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Preface
  • Contributing Authors
  • Introduction
  • Road Log
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Emplacement of Holocene silicic lava flows and domes at Newberry, South Sister, and Medicine Lake volcanoes, California and Oregon
Series title Scientific Investigations Report
Series number 2017-5022
Chapter I
DOI 10.3133/sir20175022I
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Volcano Science Center
Description viii, 41 p.
Country United States
State California, Oregon
Other Geospatial Medicine Lake Volcano, Newberry Volcano, South Sister Volcano
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details