USGS Volcanoes (original) (raw)

On October 7, 1805, Lewis and Clark and the "Corps of Discovery" began their journey down the Clearwater River and into the volcanics of the Pacific Northwest. The Corps travelled from the Clearwater to the Snake and down the "Great Columbia", finally reaching the Pacific Ocean on November 15, 1805. Along the journey they encountered the lava flows of the Columbia Plateau, river channels carved by the great "Missoula Floods", and the awesome beauty of five Cascade Range volcanoes.

Map, Lewis and Clark in the Pacific Northwest
(Click map for brief summary about the area)

[ Top of Page]

Mount Adams, Washington, click for more information Mount Adams, Washington Mount Adams, at 12,276 feet, is one of the largest volcanoes in the Cascade Range. Lewis and Clark either mis-identified this peak, or simply called it a "a high humped Mountain to the East of Mt St. Helians". [More]
Mount Hood, Oregon, click for more information Mount Hood, Oregon Mount Hood, at 11,245 feet high, dominates the Cascade skyline from the Portland metropolitan area to the wheat fields of Eastern Oregon. Mount Hood is the fourth highest peak in the Cascades and the highest in Oregon. The volcano had erupted a few years before the Lewis and Clark journey. [More]
Mount Jefferson, Oregon, click for more information Mount Jefferson, Oregon The 10,495-feet-high Mount Jefferson was named by Lewis and Clark on March 31, 1806. They named it after the then President Thomas Jefferson, who funded their journey. [More]
Mount Rainier, Washington, click for more information Mount Rainier, Washington Mount Rainier is the highest (14,410 feet) and third-most voluminous volcano in the Cascades. The Mountain is, however, the most dangerous volcano in the range, owing to the large population and to the huge area and volume of ice and snow on its flanks that could theoretically melt to generate debris flows during cataclysmic eruptions. [More]
Mount St. Helens, Washington, click for more information Mount St. Helens, Washington Mount St. Helens was 9,677 feet high before May 18, 1980, when it erupted sending a plume of ash 15 miles high, and destructive mudflows miles downriver. Today the peak is 8,364 feet high, with a north-facing crater and a new lava dome. Lewis and Clark observed this peak along the journey and comment on the fact you can see Mount St. Helens from the mouth of the Columbia River. [More]

[ Top of Page]

Map, the Volcanoes of Lewis and Clark, click to enlarge Map, the Volcanoes of Lewis and Clark, click to enlarge Map, Columbia River and Tributaries, click to enlarge Map, Columbia River Flood Basalts, click to enlarge Map, Geologic Map of Washington State, 1974 USGS, click to enlarge Map, Missoula Floods, click to enlarge

  1. Lewis and Clark in the Pacific Northwest
    Volcanoes, Lava Flows, Rivers, Canoe Camp, and Fort Clatsop. A map of the volcanic area Lewis and Clark and the "Corps of Discovery" passed on their way to the Pacific. (Click map to enlarge)
  2. Lewis and Clark Volcano Sitings
    Marked locations where Lewis and Clark sited the "Volcanoes of Lewis and Clark". Mount Rainier, Mount St. Helens, and Mount Adams are in Washington State. Mount Hood and Mount Jefferson are in Oregon. Lewis and Clark named Mount Jefferson. (Click map to enlarge).
  3. The Columbia River and its Tributaries
    The Columbia River and its tributaries form the dominant water system in the Pacific Northwest. The mainstem of the Columbia rises in Columbia Lake in British Columbia, Canada. After flowing a circuitous path for 1,270 miles, the Columbia joins the Pacific Ocean near Astoria, Oregon. The major tributaries of the Columbia are the Kootenai, Flathead/Pend Oreille/Clark's Fork, Snake, and Willamette. The largest of these, the Snake, travels 1,038 miles from its source in Yellowstone National Park in Wyoming. The massive Columbia River basin was formed 12,000 to 19,000 years ago near the end of the last Ice Age. The Columbia river was named in 1792, by American Captain Robert Gray, after his ship "Columbia". (Click map to enlarge).
  4. Columbia River Flood Basalts
    The Columbia River passes through lava flow upon lava flow. During late Miocene and early Pliocene times (between 17 and 6 million years ago), one of the largest basaltic lava floods ever to appear on the earths surface engulfed about 63,000 square miles of the Pacific Northwest. Over a period of perhaps 10 to 15 million years lava flow after lava flow poured out, eventually accumulating to a thickness of more than 6,000 feet. Over 300 high-volume individual lava flows have been identified, along with countless smaller flows. Numerous linear vents, some over 90 miles long, show where lava erupted near the eastern edge of the Columbia River Basalts. Older vents were probably buried by younger flows. As the molten rock came to the surface, the earths crust gradually sank into the space left by the rising lava. The subsidence of the crust produced a large, slightly depressed lava plain now known as the Columbia Basin (Plateau). The ancient Columbia River was forced into its present course by the northwesterly advancing lava. (Click map to enlarge).
  5. Geologic Map of Washington State
    With Select Stratigraphic Units. (Click map to enlarge).
  6. The Cordilleran Ice Sheet and the Missoula Floods
    With the beginning of the Pleistocene time, about one million years ago, cooling temperatures provided conditions favorable for the creation of great sheets of moving ice. Thus began the Ice Age. At the end of the last Ice Age, a finger of the Cordilleran ice sheet crept southward into the Idaho panhandle, forming a large ice dam that blocked the mouth of the Clark Fork River, creating a massive lake 2,000 feet deep and containing more than 500 cubic miles of water. Glacial Lake Missoula stretched eastward for some 200 miles and contained more water than Lake Erie and Lake Ontario combined. When the highest of these ice dams failed, lake water burst through, shooting out at a rate 10 times the combined flow of all the rivers of the world. This towering mass of water and ice literally shook the ground as it thundered toward the Pacific Ocean, stripping away hundreds of feet of soil and cutting deep canyons -- "coulees" -- into the underlying bedrock. With flood speeds approaching 65 miles per hour, the lake would have drained in as little as 48 hours. Over time the Cordilleran ice sheet continued moving south and blocked the Clark Fork River again and again, recreating Glacial Lake Missoula. Over approximately 2,500 years, the lake, ice dam and flooding sequence was repeated dozens of times, leaving a lasting mark on the landscape. (Click map to enlarge). -- Excerpts from: U.S. Army Corps of Engineers Website, 2002, USGS/NPS Geology in the Parks Website, 2002, U.S. National Park Service, Lake Roosevelt National Recreation Area Website, 2002, U.S. National Park Service, Ice Age Floods Website, 2002, U.S. National Park Service, National Natural Landmarks Program Website, 2002, and U.S. Forest Service, Columbia Gorge National Scenic Area Website, 2002

[ Top of Page]

Lewis and Clark and the "Corps of Discovery"

"take notice of the country you pass through, it's general face, soil, river, mountains, it's productions animal, vegetable, & mineral so far as they may be new to us & also be useful; the latitudes of places ...; the names, numbers, & dwellings of the inhabitants, and such particularities as you can learn of them." -- President Thomas Jefferson - April 30, 1793

In 1803, President Thomas Jefferson commissioned Meriwether Lewis, who along with his friend William Clark, lead an expedition on an epic journey to explore the headwaters of the Missouri River and find an overland route to the Pacific Ocean by way of the Columbia River. The "Corps of Discovery" departed Camp DuBois near Wood River, Illinois, on May 14, 1804, and proceeded up the Missouri River using a keelboat and two "pirogues". After several councils with the Indian Tribes on the lower Missouri River, and the unfortunate death of Sergeant Floyd near present Sioux City, Iowa, the party reached the Knife River Indian Villages, near present Washburn, North Dakota. There they built Fort Mandan and spent a productive winter gathering information about the Indian Tribes and the lands to the west. They also recruited as interpreters, the Frenchman Toussaint Charbonneau and his Shoshoni wife, Sacagawea. In the spring of 1805, the permanent party continued up the Missouri River in the pirogues and dugout canoes. After an arduous portage around the Great Falls of the Missouri, they reached the headwaters of that great river. Now on foot, the party encountered a band of Shoshoni Indians, coincidentally led by Sacagawea's brother Cameahwait. The Shoshoni assisted the expedition by providing horses and a guide to cross the rugged Bitteroot Mountains. After a difficult crossing on what is now known as the Lolo Trail, the party met the friendly Nez Perce Indians. They left their horses with the Indians and once again made canoes. Navigating down the Clearwater, Snake, and Columbia Rivers, the Corps of Discovery reached the Pacific Ocean in November 1805. The party built Fort Clatsop on the south side of the Columbia River near present Astoria, Oregon, where they spent a cold, rainy winter. In the spring and summer of 1806, the expedition made their way back across the mountains, explored several major rivers in present day Montana, and made their way back down the Missouri River to St. Louis, arriving on September 23, 1806. The Lewis and Clark National Historic Trail is approximately 3,700 miles long, begins near Wood River, Illinois, and passes through portions of Missouri, Kansas, Iowa, Nebraska, South Dakota, North Dakota, Montana, Idaho, Oregon, and Washington. -- U.S. National Park Service, 2002, Fort Clatsop National Memorial Website, and Lewis & Clark National Historic Trail Website

[ Top of Page]

About the Reference Materials

Main Text Excerpts from:
History of The Expedition Under the Command of Captain's Lewis and Clark, to the Sources of the Missouri, thence Across the Rocky Mountains, and down the River Columbia to the Pacific Ocean, Performed during the years 1805-5-6, By order of the Government of the United States. Prepared for the Press by Paul Allen, Esquire., Vol. II. Published by Bradford and Inskeep, Philadephia, and Abm. H. Inskeep, New York. J. Maxwell, Printer., 1814. ("Biddle/Allen Publication") Online at: Library of Congress/American Memories Website, 2002; Collection from: The First American West: The Ohio River Valley 1750-1820, Special Collections Research Center, University of Chicago Library, and The Filson Historical Society. About the Biddle/Allen publication:
Captain Lewis was supposed to have edited the journals for publication, but he met with an untimely death, probably by murder, while traveling through Tennessee in 1809. The task then fell to Clark, who asked the Philadelphia lawyer Nicholas Biddle, to complete the job. Biddle agreed, but soon passed the work on to Paul Allen, a Philadelphia journalist. The journals were finally edited and made ready for publication in 1812, but were not published until February 20, 1814. Originally, an edition of 2,000 was to be printed, but when missing copies were tallied and defective copies weeded out, only 1,417 remained. These sold at six dollars a copy. The Biddle-Allen revision of the Lewis and Clark journals left intact the raw quality of diaries written in the wilderness, retaining their sense of danger and high adventure. -- Excerpt from: Treasures of the University of Delaware Library Additional Quotations and Journey Logs from:
The Journals of the Lewis & Clark Expedition, Gary E. Moulton, Editor, University of Nebraska Press, Lincoln and London, volumes 5, 6,7, 9, 10, and 11About the Moulton publications:
Dr. Gary Moulton at the University of Nebraska has compiled the first complete set of journals relating to the Lewis & Clark Expedition. The result of this project (beginning in 19__) is a 13-volume set (as of November, 2002) that includes Clark's maps, the Journals of Meriwether Lewis, William Clark, Patrick Gass, Joseph Whitehouse, John Ordway, and Charles Floyd. This set of books are the most accurate copies of the actual journals. Previous versions of the Journals have actually been condensed collections and interpretations of the known journal documents. -- Information courtesy: The Lewis & Clark Expedition Website, 2002 A History of Lewis and Clark Journals:

[ Top of Page]

USGS Lewis and Clark Links

[ Top of Page]