Volcanoes and Superquakes: Living with Geologic Hazards in the Pacific Northwest

For most residents of the Pacific Northwest, the region’s spectacular landscape — from rugged coastlines to towering, glacier-clad peaks — seems permanent and unchanging. For the Native Americans who inhabited the area for millennia before Anglo-Americans settled it, however, the land’s apparent stability and tranquility was recognized as a dangerous illusion.

As their oral traditions testify, many native tribes knew what contemporary scientists have only recently discovered: the Pacific Northwest owes much of its scenic beauty to almost unimaginable geologic violence, catastrophic earthquakes and devastating volcanic eruptions. Geologists studying deposits left by prehistoric earthquakes and tsunamis — giant sea waves tens of feet high — have learned that the coasts of Washington, Oregon, and northern California are vulnerable to the same kind of quake-generated tsunami disaster that killed about 200,000 people around the Indian Ocean in December 2004. During the last several thousand years, giant temblors have repeatedly convulsed the Pacific coast from near Eureka, California, to Vancouver Island, British Columbia, most recently in January, 1700.

The 1700 event — dated by a combination of radiocarbon techniques, the counting of annual tree rings, and written records of a tsunami that struck Japan in late January that year — registered a magnitude of 9.0, at least 30 times more powerful than the quake that shattered San Francisco in 1906. Tribal memories of that cataclysm include a northern California tale in which intense shaking was accompanied by floodwaters that swept away an entire village, sparing only those who had fled to high ground before the tsunami rolled ashore. On the Olympic Peninsula of northwest Washington, the Hoh and Quieleute tribes interpreted the upheaval as a fierce battle between two supernatural forces, Thunderbird and Whale.

In creating tales about the geologic events and processes that shaped their physical environment, Native storytellers typically presented a united worldview that encompassed both material and spiritual components. In the Bridge of the Gods legend, which celebrates a love triangle involving three volcanic peaks bordering the Columbia River — Hood, Adams, and St. Helens — the snow-capped mountains were not merely inert piles of rock; they were living presences with distinctive personalities.

Although it is now difficult to disentangle later Caucasian embellishments from the original tradition, a Klickitat version of the story preserves the important elements. According to Klickitat lore, long before white explorers arrived on the scene, native tribes were able to cross the Columbia River, near the present site of Cascade Locks, via a land “bridge” that was tomanowos, a creation sacred to the gods. But when the tribes became noisy and quarrelsome, Tyee Sahale (commonly interpreted as the “Great Spirit”) took steps that eventually led to the bridge’s demolition. First, he caused all the fires in their lodges to go out. Only the fire kept by Loowit, an old woman who avoided the violence that divided her people, remained burning, so all her neighbors had to come to her to rekindle their campfires. When Tyee Sahale asked Loowit to claim a reward for her generosity, she did not hesitate to name her choice: youth and beauty. Transformed into a lovely young maiden, Loowit inadvertently reignited the fires of war by attracting two aggressive suitors, both sons of the Great Spirit.

The first son, Pahto, ruled over territory north of the Columbia, while the second, Wy’east, led the Willamette people south of the river. When Pahto and Wy’east contended furiously for Loowit’s favor, hurling red-hot boulders at each other, Tyee Sahale separated them by overthrowing the bridge linking their two realms, its fragments creating the cataracts for which the adjacent Cascade Range was later named. The Great Spirit also changed the three lovers into volcanic mountains: Pahto became the broad-shouldered giant that white settlers called Mount Adams; Wy’east became Mount Hood; and Loowit, the beautifully symmetrical Mount St. Helens. It was said that Loowit (whom some tribes named Tahonelatclah or Louwala-Clough, “fire-mountain”) secretly favored the more graceful Wy’east, who burned with passion longer than Pahto, who soon fell asleep under his ermine blanket.

Besides explaining the volcanic nature of the three Guardians of the Columbia, the Bridge of the Gods tradition also evokes tribal memories of an enormous avalanche, the Bonneville landslide, that completely dammed the Columbia River only about three centuries ago, forming a rocky causeway that allowed travelers to cross the river dryshod. (Because the local tribes had no word for “bridge,” the notion that this formation was a soaring stone arch is a Caucasian invention.) It is possible that some of the large basaltic blocks forming the dam remained in place considerably after the river cut a new channel through its southern toe, about a mile south of its pre-slide course. If so, the famed Bridge of the Gods was in fact a jumbled pile of lava slabs, much as a native informant described it to a French missionary — “a long range of towering and projecting rocks” — before it collapsed, possibly in the earthquake of 1700.

By far the most frequently — and violently — active of the volcanic trio overlooking the Columbia River, Mount St. Helens opened a new chapter in her legendary career in March, 1980, when she began a series of minor eruptions that culminated in a cataclysmic outburst. Shaken by a magnitude 5.0 quake at 8:32 a.m., May 18, 1980, the entire north side of the volcano suddenly collapsed, triggering the largest debris avalanche in recorded history and unleashing a ground-hugging lateral blast that devastated 230 square miles of pristine timberland. In minutes, St. Helens’ classically perfect cone was transformed into a horseshoe-shaped wreck that faced northward toward a moonscape of gray desolation. During the initial phase of the day-long eruption, ash clouds soared almost 100,000 feet into the stratosphere, where winds carried the ash plume eastward, turning day into night across eastern Washington, northern Idaho, and western Montana. Deadly lahars, volcanic mudflows that resemble churning waves of liquid concrete, streamed down valleys heading on the mountain, destroying bridges, logging camps, and more than 200 houses and other structures before emptying into the Columbia River, temporarily closing it to shipping.

Although St. Helens’ 1980 outburst killed fifty-seven people and thousands of animals, including about 7,000 deer and elk, and caused approximately $1 billion in property losses, the eruption was relatively small compared to others in its recent geologic past. In A. D. 1479 (according to tree-ring dating), the volcano produced an explosive paroxysm six times larger than that of 1980, beginning an eruptive cycle that continued intermittently for at least 250 years. About 3,300 years ago, St. Helens disgorged so much pumice — creating a yellowish ash layer known as Yn that lies a foot thick at Mount Rainier National Park, 50 miles to the north, and extends as far northeast as Banff, Alberta — that many Native Americans had to abandon their former settlements and migrate to sites farther from the volcano’s lethal reach.

Even St. Helens’ tempestuous behavior, however, is dwarfed by the explosive violence of Mount Mazama, a volcano in southern Oregon that virtually destroyed itself.

About 7,700 years ago, Mazama — which then towered more than 12,000 feet above sea level — erupted so large a volume of material — perhaps forty cubic miles of frothy volcanic glass called pumice — that its former summit collapsed, forming the basin, five by six miles in diameter, that now holds the azure waters of Crater Lake. In the first phase of its suicidal paroxysm, Mazama ejected a column of ash that rose 30 miles into the air, showering orange-colored pumice over 500,000 square miles in eight western states and southern Canada. As new vents encircling the entire cone opened during the eruption’s second stage, roiling avalanches of incandescent pumice swept down all sides of the mountain, some traveling as far as 35 miles from the volcano. With its internal storehouse of molten rock rapidly emptied, the volcano’s upper cone subsided to fill the void, transforming a towering peak into a vast hole in the ground. As geologists observe, a comparable eruption today would create a regional disaster.

Like those of the Columbia region’s volcanic sentinels, Mazama’s tremendous outburst inspired a native tradition involving mountain deities. In 1865, Lalek, an aged Klamath chief, confided his people’s tradition to William M. Colvig, a young soldier then stationed at Fort Klamath, Oregon. According to Lalek’s story, in ancient times Llao, an underworld god who lived beneath Mount Mazama, fought against Skell, a sky god who inhabited Mount Shasta, 125 miles to the south. In their titanic conflict, all the spirits of earth and sky waged war, searing the land with sheets of flame that intermittently lit up the ash-shrouded darkness. When Skell at last prevailed, he beheaded Llao’s mountain, confining his opponent to a subterranean prison. (Although some anthropologists believe that this story of Mazma’s collapse and the origin of Crater Lake was transmitted orally from generation to generation for the last 7,000 years, others suggest that it was invented to explain the strange presence of a huge basin in a range of high peaks.)

Mazama and St. Helens are but two in a chain of geologically youthful volcanoes in the Cascade Range, which extends for 700 miles from Lassen Peak in northern California through Oregon and Washington to Mounts Garibaldi and Meager in British Columbia. During the last 350 years, at least eight have erupted: Baker, Glacier Peak, Rainier, and St. Helens in Washington; Mount Hood in Oregon; and Mount Shasta, Lassen Peak, and Cinder Cone in California. Geologists are particularly worried about future eruptions at Mount Rainer (14,411 feet), which supports a cubic mile of glacial ice, the nation’s largest single-peak glacier system south of Alaska. Hot rock ejected onto the volcano’s ice fields causes rapid melting, producing enormous lahars that rush at speeds of twenty-five to forty miles an hour downvalley before spreading out into the eastern Puget Sound lowland. About 150,000 people now live atop Rainier’s recent lahar deposits — directly in the path of future mudflows — but many more of the area’s 2.5 million inhabitants are likely to be affected when the volcano next erupts. Extensive deforestation of the Puget Sound lowlands has removed barriers that previously restricted a mudflow’s lateral extent, ensuring that future lahars will travel faster and farther than ever before. Even in locations untouched by lahars, the loss of crucial highways, bridges, businesses, residential developments, and shopping centers will disrupt innumerable lives.

Because its future activity will impact a densely populated region, including the Seattle-Tacoma area, Mount Rainier has been officially designated the most dangerous volcano in America.

Why does the Pacific Northwest’s scenic splendor involve so much geologic violence? Both the region’s propensity for giant earthquakes and volcanic eruptions result from its geologic setting, a vulnerable position where two huge slabs of the earth’s crust collide about 30 to 90 miles off the Pacific coast. Washington and Oregon form a link in the notorious “Ring of Fire,” a belt of intense seismic and volcanic activity encircling the Pacific Ocean. The circum-Pacific “Ring of Fire,” in turn, results from a worldwide geologic process known as plate tectonics. Pulsating like a living organism, the earth’s crust is fragmented into about sixteen major and several minor tectonic plates, rocky barges that carry continents or ocean basins on their backs. Heat circulating through the earth’s interior keeps the plates in constant motion, pulling apart, rubbing against each other, or colliding together as they slide over an underlying zone of hot plastic material, the mantle. Deep beneath the earth’s surface, the highest concentrations of internal heat form convection cells, similar to those in a pot of boiling water. This cycle of currents in the mantle, the 1,800-mile-thick region between the earth’s metallic core and its brittle outer shell, keeps the plates moving, buoying the crust in one place and tugging it down in others.

Linear rift zones at which plates separate are called divergent boundaries, or spreading centers, where magma (molten rock underground) oozes up through long fissures in the crust, creating submarine mountain ranges such as the Mid-Atlantic Ridge and the East Pacific Rise. As the magma rises along linear spreading centers in ocean basins, such as the Juan de Fuca Ridge off the Pacific Northwest Coast, it shoulders the surrounding rock aside, pushing opposite sides of the ocean floor away from each other and toward the neighboring continents. When the dense, relatively thin seafloor, composed of basaltic lava, collides with the much thicker and lighter granitic rock composing the continents, the heavier, denser ocean floor is forced downward, gradually sinking into the mantle beneath the continental margins. Where ocean and continental plates converge, a subduction zone typically forms. As the water-saturated oceanic plate plunges deeper into the mantle, the descending slab encounters increasingly high temperatures. The addition of water to subterranean hot rocks lowers their melting point and generates new magma. Hotter and lighter than the surrounding rock, the magma rises into the continental crust, typically forming underground reservoirs called magma chambers. When the chemically evolving magma becomes more buoyant than the surrounding rock and migrates to the earth’s surface, a new volcano is born or an old one revives.

Plate convergence forms subduction zones around most of the Pacific basin, triggering some of the world’s greatest earthquakes and volcanic eruptions, including those in Alaska, Japan, Indonesia, Central America, South America and the Pacific Northwest. The two most powerful earthquakes ever recorded — a magnitude 9.5 event in Chile in 1960 and a 9.2 quake in Prince William Sound, Alaska, in 1964 — both centered at subduction zones and both generated deadly tsunamis that swept thousands of miles from their source.

At the Cascadia subduction zone — which extends about 700 miles from northern California to British Columbia — two relatively small fragments of the Pacific plate, the Juan de Fuca plate and the even smaller Gorda plate to the south, are sinking beneath the northwest margin of North America, moving eastward at a rate of one or two inches a year. Partial melting of these descending slabs generates the magma that fuels the Cascade volcanoes from Lassen to St. Helens to Canada’s Garibaldi.

Subduction of the Juan de Fuca plate also produces the colossal earthquakes that have catastrophically jolted the Pacific Northwest at least a dozen times in the last 7,700 years, most recently in 1700. Geologists believe that the Cascadia subduction zone generates particularly high magnitude earthquakes because the Juan de Fuca slab does not descend smoothly or continuously beneath the continent’s edge. Instead, the two plates become locked together, causing stress to build until the descending plate breaks free and plunges suddenly many tens of feet downward, commonly pulling sections of the coastline down five or six feet with it. In the 1700 earthquake, which ruptured the fault for most of its length, subsidence was greatest along the northern Oregon and southern Washington coast, where large tsunamis also swept far inland, inundating town sites from Grays Harbor to Coos Bay. During quiet interludes between major quakes, the coastline rebounds gradually, rising about 1.5 inches per year — until the next great convulsion yanks it down again.

Although the interval between Cascadia superquakes averages about 550 years, they do not occur regularly; interludes between them vary from 200 to 1,000 years, making prediction of the next magnitude 9.0 temblor impossible.

As if a vulnerability to gigantic subduction temblors were not enough, the Pacific Northwest also has two other major sources of seismic threat: ruptures within sections of the already subducted Juan de Fuca slab and fault movement in the brittle continental crust. Perhaps because of a bend in the subducted slab beneath the area, intraplate earthquakes tend to center in the Puget Sound region. Washington’s three most damaging quakes in historic time, those of 1949, 1965, and 2001 originated when parts of the already subducted slab fractured far below the surface. Because their foci were so deep, about 30 to 35 miles underground, seismic waves had lost much of their energy by the time they reached the surface, muting their destructiveness. Even so, the magnitude 7.1 temblor of 1949 killed eight people and caused $25 million in damage, a financial toll that would be much larger if the quake were repeated today. Another seven people died in the 1965 event, which was centered between Seattle and Tacoma. The Nisqually quake of February 28, 2001 originated at almost the same underground location as that of 1949, but had a magnitude of only 6.8. State officials tabulated its cost at between $2 and $4 billion.

The third category of Pacific Northwest earthquakes originates on faults in the North American plate. Historically, the strongest earthquake from this source (estimated magnitude of 6.8) occurred in 1872. Centered near the town of Entiat, Washington, about 17 miles north of Wenatche, it was felt on both sides of the Cascade Range , from Walla Walla in eastern Washington to Port Townsend, Tacoma and Olympia, in the western part of the state. Because quakes originating in the continental crust typically occur at much shallower depths than those in subducted slabs, they cause much more intense shaking at the ground surface and are more damaging to human-made structures.

When previously unknown active faults in the continental plate were discovered crossing the Puget Sound area a couple of decades ago, geologists realized that the region’s largest cities run a high risk of seismic disaster. The Seattle Fault, which slices at least 40 miles through the crust from an area east of Lake Washington across downtown Seattle to Bainbridge Island, produced a topography-changing jolt about A. D. 900. Some locations were suddenly raised as much as 20 feet above their previous levels, while others dropped an equal distance. Like water sloshing in a bathtub, tsunamis swept inland over the shores of Puget Sound, including what is now the Seattle waterfront.

A recent study envisioning damage from a magnitude 6.7 event on the Seattle Fault estimates a loss of $33 billion and fatalities and injuries totaling almost 8,000.

Renewed activity at some of the Cascade volcanoes, particularly those near large population centers, could exact an even larger toll. If Mount Rainier were to stage a major eruption — or even a small eruption that generated a large mudflow — the economic and human losses would be staggering. Although not as volatile as Mount St. Helens, Rainier threatens more densely populated areas on valley floors many tens of miles from the volcano. About 5,600 years ago a relatively minor explosive event caused Rainier’s former summit to collapse, triggering the Osceola Mudflow — a cubic mile in volume — that streamed 65 miles from its source and buried 210 square miles, including the sites of Buckley, Enumclaw, Auburn, Sumner, Puyallup, and Tacoma, under thick muck. In a matter of hours, rocks that had once stood more than 15,000 feet above sea level, were submerged beneath the waters of Puget Sound.

Although the largest known, the Osceola is only one of approximately 60 similar lahars that Rainier has produced during the last several millennia. About 600 B.C., part of Rainier’s west face collapsed, opening a wide scarp known as the Sunset Amphitheater and generating the Round Pass lahar, a wave of rock and mud initially 1,000 feet high, that poured many miles down the Puyallup River Valley. Only 500 years ago avalanching rock from the same area high on Rainier’s west side produced the Electron Mudflow, which entombed a forest at the site of Orting before streaming down the Puyallup valley at least as far as Sumner. Although Orting has installed a warning system to alert residents that a lahar is on its way, people would have little more than 45 minutes in which to evacuate to high ground.

Rainier’s eruptive activity commonly produces destructive mudflows on several sides of the mountain at once. Between about A. D. 900 and 1000, eruptions produced a series of voluminous lahars that swamped both forks of the White River on Rainier’s east side, as well as the Nisqually River valley on the south flank, depositing a thick fill that raised canyon floors 60 to 90 feet above their present levels. During this extended eruptive episode, some mudflows traveled 65 miles into the Puget Sound basin, covering the lower Duwamish, White, and Puyallup valleys in rocky sludge up to 30 feet deep and inundating the sites of Auburn and Kent. Water draining from the lahar deposits, which contained numerous pumice fragments, transported large quantities of sand to bury tidal flats in what are now Seattle suburbs near the Boeing aircraft company. These reworked sands extend as far north as the Port of Seattle Terminal 107, about two miles from Elliot Bay, the inlet along which downtown Seattle is built.

Mount Rainier’s latest minor activity, which scattered pumice over the east flank between about 1820 and 1854, apparently triggered no significant mudflows. Continuing heat and steam emission in the two overlapping summit craters, however, remind us that Rainier is only napping between eruptions. It has produced more than 20 outbursts during Holocene time, the last 10,000 to 12,000 years since the end of the last Ice Age, and geologists fully expect the volcano to revive, perhaps with catastrophic consequences to people living in its shadow.

Although the range north of Mount Rainier is essentially non-volcanic, the two highest peaks in Washington’s heavily glaciated North Cascades — Mount Baker (10,781 feet) and Glacier Peak (10,541 feet) — are volcanoes that pose serious threats to towns and cities located far from their ice-shrouded summits. In March, 1975, exactly five years before St. Helens began the series of steam explosions that culminated in the cataclysm of May 18, 1980, Baker abruptly intensified its heat and steam emission, ejecting minor quantities of ash that thinly veneered the Boulder Glacier on its east flank and increasing its release of hydrogen sulfide gas. As ice melted to form an acidic lake in Sherman Crater, a bowl-shaped vent located a half mile south of the main summit, the U. S. Geological Survey (USGS) closely monitored the volcano, eventually closing the Baker Lake recreational area, at Baker’s eastern foot, to public access. Steam and sulfur production declined after 1976, and resorts and campgrounds were reopened, but the discharge of steam and heat remains significantly above pre-1975 levels.

Baker’s largest historic eruption occurred in 1843, when steam explosions blew fragments of old rock from Sherman Crater and deposited layers of ash for four miles northeast of the volcano. The historic episode, which lasted intermittently until about 1880, emitted no fresh magma, but partial collapse of the east rim of Sherman Crater directed avalanches and lahars down the eastern slopes toward Baker Lake.

As at Mount Rainier, Baker’s chief hazard — that most likely to affect populated areas many miles downvalley from the volcano — consists of debris avalanches and lahars. According to a 1995 USGS hazards evaluation, partial collapse of the upper cone 6,500 years ago caused a lahar that traveled down the Nooksack River into Bellingham Bay, burying the sites of several small towns, including Deming, Everson, and Lynden. If the west wall of Sherman Crater were to fail, the resulting mudflows could pour into Lake Shannon, perhaps causing dam failure and floods that would sweep down the channel of the Skagit River, inundating larger settlements on its flood plain, including Sedro Woolley, and Mount Vernon.

Because of its location deep within the rugged North Cascades 70 miles northeast of Seattle, Glacier Peak, invisible to travelers on busy Interstate 5, is perhaps the least known volcano in the range. It is also one of the most potentially dangerous. Like Mount St. Helens, Glacier Peak is highly explosive, erupting two of the largest and most widely distributed pumice layers of any Cascade volcano since the most recent Ice Age glaciers began to retreat. Besides blanketing vast areas of the Pacific Northwest and southern Canada in thick ashfalls about 13,000 years ago, the volcano has repeatedly produced large-volume avalanches of hot pumice and extensive mudflows.

Glacier Peak has been sporadically active during Holocene time, erupting thick viscous lava that piles up to form lava domes similar to that now growing in St. Helens’ crater. When steep domes high on the cone collapse or are disrupted by steam explosions, they form avalanches of hot gas and incandescent rock fragments — pyroclastic flows — that rapidly melt glacial ice, generating the floods and mudflows that have characterized the volcano’s behavior during the last few thousand years. Last active during the eighteenth century, when it ejected ash that now covers nearby ridgetops, Glacier Peak is not expected to erupt in the immediate future.

A more likely candidate for renewed activity during our lifetimes is Mount Hood, at 11,239 feet Oregon’s highest peak and most recently active volcano. Although Hood had enjoyed a long sleep of almost 12,000 years before it reawakened about 1,500 years ago, it has been one of the more vigorously active Cascade volcanoes since then, a fact abundantly documented in Native American legends. About A. D. 500, magma rising into Hood’s erosion-scarred cone caused the volcano’s south flank to collapse, initiating avalanches and mudflows that traveled down the Sandy River all the way to the Columbia. Like Glacier Peak, Hood produces a viscous magma called dacite, which, flow-resistant, typically piles up to form bulbous lava domes that shatter and collapse, generating pyroclastic flows and lahars. During this extended eruptive cycle, known as the Timberline episode, rising and collapsing domes at a vent south of Hood’s summit gradually created a broad debris fan that now mantles the volcano’s southern flank. Built in 1937 near the debris fan’s eastern margin, elegantly rustic Timberline Lodge now draws tens of thousands of skiers, snowboarders, and other winter sport enthusiasts every year to the unusually smooth expanse of the volcano’s south slope. Located at an elevation of 6,000 feet, the Timberline resort provides the nation’s only developed ski center open throughout the year, a distinction partly owed to the nature of Hood’s late Holocene activity.

Hood’s most recent eruptive period — the Old Maid episode — began during the winter of 1781-1782, only a decade before Robert Broughton, first lieutenant of George Vancouver’s 1792 exploratory voyage down the Pacific Northwest coast, named the peak for Lord Samuel Hood, admiral of the British navy. Arriving too late to witness the eruption, Broughton nonetheless observed some of its effects, which included a long submerged sandbar extending from the mouth of the Sandy River across the Columbia and logs that were stranded up to twelve feet above the river’s surface. When Lewis and Clark arrived at the Sandy River thirteen years later, Clark described the Sandy as so full of sediment that it ran only about four inches deep. Attempting to wade across, Clark was astonished to find ‘the bottom a quick Sand [sic.] and impassible.” The Sandy River, which presently runs through a deep, narrow gorge to the Columbia, was then choked with debris from a large mudflow originating high on Mount Hood.

The Old Maid period, named for typical mudflow deposits it created on Hood’s west flank, apparently began with explosive eruptions that blasted away the dome formed during the Timberline episode. When fresh magma rose into the vent, located about 1,000 feet below and south of the summit, it erected a new dome, Crater Rock, the prominent lava knob now seen at the apex of the south-side debris fan. Hot rock avalanching from the growth of Crater Rock initiated pyroclastic flows that traveled down the White River on Hood’s southeast flank, as well as onto the Sandy Glacier on the volcano’s west side, causing the massive lahars that filled the Sandy River gorge. Searing clouds of ash-permeated gas — pyroclastic surges — sweeping downslope from Crater Rock killed stands of trees near timberline, creating the silvery “Ghost Forest “ now visible on a ridgetop east of Timberline Lodge.

Although both Vancouver’s crew and the Lewis and Clark expedition of 1805-1806 missed seeing Hood in action, later settlers recorded minor explosive events during the mid-nineteenth century. Writing in the Everett Record (1902), W. F. Courtney offered an account of activity in September, 1859:

We were camped on Tie [Tygh] Ridge about thirty-five miles from Mt. Hood. ..It was about 1:30 o’clock in the morning when suddenly the heavens lit up and from the dark there shot up a column of fire. With a flash that illuminated the whole countryside with a pinkish glare, the flames danced from the crater. For two hours we watched, the mountain continued to blaze at irregular intervals, and when morning came Mt. Hood presented a peculiar sight. His sides, where the day before there was snow, were blackened as if cinders and ashes had been thrown out.

Six years later, John Dever, a soldier stationed at Vancouver, witnessed an early morning eruption, which he described in a letter to the Portland Oregonian (September, 1865):

Between the hours of 5 and 7 o’clock, and as the morning was particularly bright for this season of the year, my attention was naturally drawn toward the east. Judge, then, of my surprise to see the top of Mount Hood enveloped in smoke and flame. Yes, sir, real jets of flame shot upwards seemingly a distance of fifteen or twenty feet above the mountain’s height, accompanied by discharge of what appeared to be fragments of rock, cast up a considerable distance, which I could perceive fall immediately after with a rumbling noise not unlike distant thunder.

Although the deposits have not been positively correlated with observed historic events, Hood’s upper cone is littered with fragments of lava and pumice stones, some of which may have been erupted in 1859 or 1865.

In an unpublished letter of January 28, 1866, Portland resident Franklin A. Hinds, noted that Mount Hood had been “smoking” for the previous three months and was then still active. Laconically, Hinds also noted that Oregonians were not overly impressed by an active volcano located 50 miles distant, remarking that Hood’s occasional flare-ups did not “create so much excitement here as you would naturally suppose, the morning paper speaks of it as an item of news and it is soon again forgotten in the hum of business.” Hinds’ observation about the public’s attitude — determinedly ignoring a potential volcanic threat while pursuing business as usual — is still valid and identifies a major social impediment in preparing Pacific Northwest residents for the disastrous effects of a more powerful outburst in the future.

Although they do not yet have the techniques to predict the timing of future great earthquakes or volcanic eruptions, geologists agree that they are inevitable. Superquakes in the Cascadia subduction zone occur irregularly, but the certainty of their suddenly rearranging the coastal landscape, triggering tsunamis that will drown bays, harbors, and estuaries from Humboldt County, California to Vancouver Island, make long-term planning for their recurrence a necessity. The Cascade volcanoes typically produce two or more significant eruptions per century — at least four erupted between about 1800 and 1860 — making it likely that young adults in the Pacific Northwest will experience a volcanic crisis at some point in their lifetimes.

Among their many gifts to Anglo-American settlers, the region’s native inhabitants transmitted their memories of convulsive temblors, huge sea waves, and mountains that thundered and blazed, manifestations of the irresistible forces that rule nature and impose limits on human striving. As native traditions about the Bridge of the Gods and the battles between Llao and Skell made clear, the now deceptively quiet gods of earth, sea, and mountain could reassert their destructive power at any time.

Stephen L. Harris is a professor emeritus at California State University, Sacramento and the author of Fire Mountains of the West.