Hendrix - Geology Underfoot in Yellowstone Country

in

Yellowstone
Country

MARC S. HENDRIX

2011

Mountain Press Publishing Company

Missoula, Montana

2011 Marc S. Hendrix

Second Printing, July 2013

All rights reserved

Illustrations 2011 Marc S. Hendrix unless otherwise noted

Cover art by Thomas Moran, the Grand Canyon of the Yellowstone

Courtesy of the Library of Congress, Prints and Photographs Division

The Geology Underfoot series presents geology with a hands-on, get-out-of-your-car approach. A formal background in geology is not required for enjoyment.

is a registered trademark of Mountain Press Publishing Company.

Library of Congress Cataloging-in-Publication Data

Hendrix, Marc S., 1963

Geology underfoot in Yellowstone country / Marc Hendrix.

p. cm. (Geology underfoot)

Includes bibliographical references and index.

ISBN 978-0-87842-576-1 (pbk. : alk. paper)

1. GeologyYellowstone National Park RegionGuidebooks.

2. Yellowstone National ParkGuidebooks. I. Title.

QE79.H46 2011

557.8752dc22

2010051894

Printed by Mantec Production Company, Hong Kong

Mountain Press Publishing Company
PO Box 2399 Missoula, Montana 59806
(406) 7281900
www.mountain-press.com

To my family

Sites featured in this book. Numbers in yellow squares correspond to vignette numbers.

VIGNETTES

This book is designed to be an easy-to-understand introduction to the geology and geologic history of Yellowstone Country. What follows are short vignettes that highlight what I think are some of the main geologic features of this remarkable region. Some, such as Old Faithful, will be familiar to most Yellowstone visitors and deserve treatment because of their status. Most of the vignettes, however, are meant to acquaint the reader with aspects of the regions geology that may not be as well known but are equally, or perhaps even more, fascinating. Throughout the book Ive tried to provide a sense of the tools and techniques scientists use to understand the geologic events preserved in rocks and sediments. Ive also highlighted a few of the ways in which the world-class geology of Yellowstone Country has served, and will continue to serve, as a resource in the furthering of human knowledge. Above all, I hope the contents of this book will inspire readers to visit Yellowstone Country, take a few steps out of their vehicles, and see, with new eyes, the immensely powerful forces and wonderfully colorful history so well preserved in this one-of-a-kind international treasure.

The stops in the book occur in a variety of settings, including roadside pullouts, the shoulders of roads, and along trails maintained by the National Park Service and U.S. Forest Service. A few occur in the backcountry and require part or all of a day to access. At each stop, please exercise a high level of caution, particularly along Yellowstones busy roads, on which drivers quite often are distracted by the scenery or various animals. Those readers willing to venture to stops off the road should bring drinking water, food, ample clothing, and sunscreen. The high elevations of Yellowstone National Park often leave visitors surprisingly winded, and it is easy to underestimate the amount of exertion required to undertake what might seem like a relatively short stroll. Yellowstones weather is also quite unpredictable. It is not unusual for seemingly mild sunny days to quickly evolve into something much less benign, like a summer cloudburst or a late spring or early autumn snow flurry. Remember that it is illegal to deface or take any rocks or other natural feature from the park, and the same applies to national forest land outside the park, where special permits are required for all collecting. As you enjoy Yellowstone Country, please treat it with the utmost care so future generations are able to experience its marvelous geologic features in the same way that you enjoyed them.

This book simply would not have been possible without the consistent support of my family, friends, and professional colleagues. In particular, I wish to acknowledge and thank James Lainsbury, the main editor with whom I worked at Mountain Press, for his continued encouragement and support, keen professional insight, and many hours of dedication to working on this project. I would also like to thank Beth Judy for the critical early role she played in getting me started with Mountain Press. I would like to thank my coworkers in the University of Montana Geosciences Department for numerous long and thoughtful conversations regarding many of the ideas presented in this book and my interpretation of the technical literature on those subjects. In this regard, I would especially like to thank Graham R. Thompson, who reviewed an early version of this manuscript, James W. Sears, and Steven D. Sheriff. Other colleagues I would like to acknowledge for the insights they provided regarding Yellowstone Country geology or other related topics addressed in this book include Steve Graham, Don Winston, Alan Carroll, Susan Vuke, Michael Hofmann, James Staub, Nancy Hinman, Jack Epstein, Judy Parrish, Lisa Morgan, Rob Thomas, Larry Smith, Mike Pope, Julie Baldwin, Joel Harper, Cheryl Jaworowski, Mike Stickney, and Rebecca Bendick.

I thank Aaron Deskins and Brian Collins for their help with the topography data used to construct the Getting There maps that appear at the beginning of each vignette. I am also grateful to Ron Blakey and the Northern Arizona University Geology Department for permission to use four paleogeographic reconstructions, and to Wade Johnson who graciously provided a high-resolution photograph of a hydrothermal explosion. Many of the geologic interpretations presented in this book would not have been possible without the body of formal geologic literature that exists for Yellowstone Country, and several of the figures presented in this book were modified from figures published elsewhere. As such, I would like to formally recognize those works listed in the Sources of More Information section that appears at the end of the book.

This book required a dedicated field effort over parts of six field seasons and involved the assistance, support, and encouragement of many individuals. First among these is my father, Sherman S. Hendrix, who served as field assistant over four field seasons and provided the main inspiration for this work. Important additional field assistance for which I am grateful was provided by Brigette Hendrix, Matthew P. McArdle, Denison Von Maur, Greg Lovellette, and Charles Cash. Throughout this project, I received critical support and encouragement from my family and would like to thank especially my wife, Brigette, whose continuous support, encouragement, and companionship made this work possible, as well as my mother, Carol, and sister, Robin. Lastly, I wish to thank Gabriel and Michael Hendrix, our two sons, for providing important additional inspiration.

Around the world, the name Yellowstone conjures images of stunning yet accessible natural beauty. Visitors to Yellowstone Countrythe area within and surrounding Yellowstone National Parkare treated to magnificent scenes that include rugged mountains, colorful cliffs, and broad valleys often dotted with big game animals. Within the park itself, the rising steam and bizarre white landscapes of geologically active thermal features contrast with pastoral grassy meadows, some of which are strewn with large boulders. Those able to leave their vehicle and traverse on foot for even short distances can experience cool mists drifting upward from a wonderful array of waterfalls, sulfurous aromas billowing from cauldrons of bubbling hot mud, and geysers spewing scalding water skyward. Though much of the Yellowstone region includes sharp ridgelines and prominent peaks towering over deep, forested valleys, the heart of the park is a surprisingly subdued landscape where vast coniferous forestsmany with sweeping scars still visible from wildfirescarpet a series of low, rolling ridges.