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Washington State History
Chapter 1: Volcanoes
Volcanic Era: Timeline
 Paleozoic Era (570 -230 million years ago)
 Early mountain building stages of the Rocky
Mountains
 Mesozoic Era (230-63 million years ago)
 Rockies constructed forming W. edge of North
America
 Tectonic plate shifting leads to Cascade Mts.
 Cenozoic Era (63 million-present)
 Columbia Plateau formed by lava flows & ice
erosion
 Olympic Mountains are uplifted (tectonic plates)
 Formation of all major PNW volcanoes
 Mt. St. Helen’s eruption (1980)
Volcanic/Glaciation Era
Columbia Plateau (pg 12)—
 Formed over millions of years by water and ice
erosion, siltation, lava flows, volcanic eruptions
Volcanic Era
•Cascade Mountains
• The range is 600+ miles
long
• From B.C. to California
• Volcanoes:
• Mt. Baker (10,778 ft)
• Glacier Peak (10, 436)
• Mt. Rainier (14,411)
• Mt. St. Helens (8,365)
• Mt. Adams (12,307)
Olympic Mountains
•Peninsula
• Surrounded
by water on 3
sides
•Volcano
• Mt. Olympus
(7,980)
Volcanic Era…
 The “Ring of Fire”
 A worldwide zone of frequent volcanic and
earthquake activity.
 It surrounds the Pacific Ocean
 421 known volcanoes
Mt. St. Helens
 Formation
 4.1 Richter scale earthquake on March 20, 1980
 This was the beginning of the formation of the
craters
 “No one foresaw the impending disaster, even with
the increased earthquake activity, the minor ash
plumes, and the small eruptions that occurred
almost daily.”
 The “Bulge”
 Growing on the north side
 4-5 ft/day
 Governor Dixy Lee Ray created the “Red Zone.”
Mt. St Helen’s Eruption
 May 18,1980
 1,300 ft blown off
 Effects
 Death and destruction
 57 killed
 Animals
 156 sq miles of forest—enough wood to build
84,000 homes
 Melted 140,000 acres of snow and ice
 Mighty Columbia clogged. 40 ft deep18 feet
deep from debris
Washington State History
Chapter 1: Glaciation
Glaciation Timeline
 Pleistocene Epoch (1 million years ago)
 The Puget Lobe penetrated western
Washington south to present day Olympia
 The Okanogan Lobe moved along
Okanogan River and blocked Columbia
River
 Last Ice Age (40,000 years ago)
 Lake Missoula Floods
 Columbia Lake formed
Puget
Okanogan
Polson
Glaciation
 The Continental Glaciers
 A “swinging” motion—advanced and
receded each time making a greater impact
 Shaped land through weathering, ice, water,
and wind erosion
 Cordilleran Ice Sheet
 3 Major “Lobes” in PNW
 Puget Lobe
 Okanogan Lobe
 Polson Lobe
Formation and Movement of
Glaciers
Alan Kearney’s photos showing South Cascade Glacier’s
retreat, 1981 to 2006.
Puget Lobe (22)
 Pushed South into Puget Sound.
 Scattered the Puget Sound lowlands between the
Cascades on the east and the Olympics on the
west.
 Formed San Juan Islands
Okanogan Lobe (22)
 Effectively blocked the Columbia River at today’s
Grand Coulee Dam. Coulee? A canyon carved out
by glaciers.
 Columbia Lake formed and overflowed south
 The overflow eroded the landscape
 Led to the creation of…
 Grand Coulee
 Irrigates a million acres of fertile farmland
 Banks Lake
 Dry Falls (24)
 Largest waterfall 40-50x greater water
Grand Coulee Dam
Dry Falls
 Green Douglas firs where the waters
cut through.
Down her wild mountains and canyons
she flew.
Canadian Northwest to the ocean so
blue,
Roll on, Columbia, roll on!
 CHORUS: Roll on, Columbia, roll on.
Roll on, Columbia, roll on.
Your power is turning our darkness
to dawn,
Roll on, Columbia, roll on.
 Other great rivers add power to
you,
Yakima, Snake and the Klickitat,
too,
Sandy Willamette and Hood River,
too;
Roll on, Columbia, roll on.
Jefferson's vision would not let him rest,
An empire he saw in the Pacific
Northwest.
Sent Lewis and Clark and they did the
rest;
Roll on, Columbia, roll on.
 At Bonneville now there are ships in the locks
The waters have risen and cleared all the rocks
Shiploads of plenty will steam past the docks
So roll on, Columbia, roll on
 And on up the river is Grand Coulee
Dam
The mightiest thing ever built by a man
To run the great factories and water the
land
So roll on, Columbia, roll on
 These mighty men labored by day and
by night
Matching their strength 'gainst the river's wild
flight
Through rapids and falls, they won the hard fight
So roll on, Columbia, roll on
Polson Lobe (25)
Lake Missoula Flood
 Resulted in the formation of a
large glacial lake called Lake
Missoula
 (a) Formed Lake Missoula
 Lake Missoula’s glacial waters
burst PAST the Polson Lobe
rushing westward toward the
Columbia River and southward
across the Columbia Plateau
 Claimed that for 2-14 days
Eastern WA was ravaged by the
Lake Missoula Flood.
 (b) Lake Missoula Flood
(c) Channeled Scablands
 The scarred and eroded
landscape from the flood
became known as the
Channeled Scablands
**Harlen J. Bretz from the University of
Chicago initiated the theory that the Lake
Missoula Flood formed the unique
Channeled Scablands of eastern Washington