Sutter Buttes—The Lone Volcano in California’s Great Valley

he volcanic spires of the Sutter 

Buttes tower 2,000 feet above 

the farms and fields of California’s 

Great Valley, just 50 miles northnorthwest of Sacramento and 11 

miles northwest of Yuba City. The 

only volcano within the valley, the 

Buttes consist of a central core of 

volcanic domes surrounded by a 

large apron of fragmental volcanic 

debris. Eruptions at the Sutter Buttes 

occurred in early Pleistocene time, 

1.6 to 1.4 million years ago. The 

Sutter Buttes are not part of the 

Cascade Range of volcanoes to the 

north, but instead are related to the 

volcanoes in the Coast Ranges to the 

west in the vicinity of Clear Lake, 

Napa Valley, and Sonoma Valley. 

In the fall of 1841 an overland party 

from the United States Exploring Expedition led by Charles Wilkes traveled down 

the valley of the Sacramento River in central California, rejoining the expedition’s 

ships later in San Francisco. The geologist 

of the expedition, James Dwight Dana, 

could not help noticing in the middle of 

that broad, flat valley an isolated cluster of 

hills that tower 2,000 feet above the valley floor “like an island in a vast prairie of 

millpond smoothness” (Dana, 1849). Dana 

explored the hills, now known as the Sutter Buttes, on October 16. He recognized 

them as the remains of an extinct volcano 

and described the various volcanic rocks 

found in them, becoming the first geologist to study this distinctive geologic and 

geographic feature of the valley. Dana also 

commented, “The whole country, we were 

told, was flooded during the winter freshets, and the deer and antelope of the plains 

then take to the Bute hills.” 

In the 170 years since the Wilkes Expedition, few other geologists have investigated 

the Sutter Buttes and the surrounding area. 

In 1929 Howel Williams, a Professor at the 

University of California at Berkeley, named 

the major landscape features and correctly 

outlined the basic geologic history (Williams, 1929). Nearly 50 years later, Williams and his Berkeley colleague, Garniss 

Curtis, revised and elaborated the volcanic 

history, aided greatly by radiometric dating of rocks (Williams and Curtis, 1977). 

In addition, the petroleum industry carried 

out investigations of sedimentary rocks 

adjacent to the Sutter Buttes and drilled 

many deep wells in search of natural gas. 

Although these investigations have determined the general history of Sutter Buttes, 

some aspects remain uncertain and are the 

subject of ongoing investigations.

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011-3024 

March 2011

U.S. GEOLOGICAL SURVEY—REDUCING THE RISK FROM VOLCANO HAZARDS

Rising 2,000 feet from the center of California’s flat Sacramento Valley near Yuba City, the isolated Sutter Buttes 

were formed by volcanism more than 1 million years ago. Their dramatic isolation is well shown in this shadedrelief image. Base map from U.S. Geological Survey elevation data.

In 1841, an overland party 

from the United States 

Exploring Expedition led by 

Charles Wilkes explored 

the Sutter Buttes, camping 

southeast of South Butte, as 

shown in this lithograph. 

Engraved by J. W. Steel from 

a drawing by Alfred T. Agate, 

an artist with the expedition. 

T
Regional Geology and Anatomy of the 

Volcano

For much of the past 75 million years, the 

area of the Great Valley of California was 

a shallow sea that connected to the Pacific 

Ocean. Rivers carried sediments from the Sierra Nevada and Klamath Mountains and deposited them in this sea. Over time, these sediments were compacted to form an enormous 

thickness of marine shale and sandstone. The 

region eventually rose to just above sea level 

Geologic map and diagrammatic cross section of the Sutter Buttes. Geology compiled from Williams and 

Curtis (1977), Thamer (1961), and new mapping by Brian Hausback. The cross section is vertically exaggerated 3X to emphasize the topography.

as an immense river valley, dominated by the 

Sacramento, Feather, and San Joaquin Rivers. Before the volcanic eruptions that formed 

the Sutter Buttes, the area was a uniform, flat 

plain on which rivers meandered back and 

forth, depositing sand, gravel, and mud on top 

of the earlier marine sediments.

The Sutter Buttes as we see them today consist of three major parts, termed by Professor 

Williams the “castellated core,” the “moat,” and 

the “rampart.” The castellated core comprises 

Miles Faults

Cross Section

 end points

Rampart Moat

Castellated Core

Moat Rampart

Quaternary sediments

Quaternary landslides

Lake bed deposits

Andesite & dacite rampart deposits

Andesite & dacite domes

Rhyolite rampart deposits

Rhyolite domes

Tertiary marine and river deposits

Cretaceous marine deposits

Cretaceous granitic rocks

Geologic Map of the Sutter Buttes Volcano

The Sutter Buttes are mostly in private 

ranches owned by families that have held 

title to the lands since the early 1900’s. In 

order to enter these lands for hiking and 

other activities, nonresidents must arrange access through groups such as the 

Middle Mountain Foundation 

(http://www.middlemountain.org). 

ACCESS TO SUTTER BUTTES

the high, craggy peaks in the center of the Sutter Buttes. These were formed by batches of 

partly molten rock (magma) that rose to the surface as viscous plugs, forming steep-sided volcanic features known as “domes.” The domes 

originally looked much like the Chaos Crags in 

Lassen Volcanic National Park. The fragmented 

surface materials of the Sutter Buttes domes 

have now been eroded away, exposing their 

resistant interior parts.

Immediately surrounding the castellated 

core is the moat. This low-lying ring of 

valleys is underlain by sedimentary rocks 

older than the Sutter Buttes volcano. These 

include layers of shale, sandstone, and conglomerate that range in age from late Cretaceous (~70 million years ago) to just before 

the Sutter Buttes first erupted about 1.6 

million years ago. The sedimentary layers 

of the moat have been uplifted and steeply 

tilted by the intruding volcanic domes of the 

castellated core, and the soft, weak shales 

and sandstones have eroded away over time 

to form the moat valleys. 

The outermost part of the Sutter Buttes is 

the rampart, a broad area of low, outwardsloping hills that were formed by flows of 

fragmental volcanic debris that moved radially 

outward from their source in the castellated 

core. Some of this material resulted from hot, 

explosive eruptions like most of the eruptions 

of Mount St. Helens, whereas other material 

was sloughed off the cooler outer parts of the 

domes and highland slopes of the castellated 

core and deposited as debris flows. 

Volcanic History of the Sutter Buttes

The first eruptions at Sutter Buttes occurred 

about 1.6 million years ago, in the early Pleistocene, when magma pushed upward through 

the thick pile of Sacramento Valley sediments. 

Some of the magma breached the surface to 

form extrusive domes in the rocky core of the 

Buttes. Explosive eruptions pulverized the extruding magma, depositing blocky fragments 

and volcanic ash that hardened into pyroclastic (“fire-broken”) rocks. 
The first lavas to erupt were light-colored, 

often white, rhyolites—rocks rich in silica 

(SiO2

) and alkalis (potassium and sodium) but 

poor in magnesium and iron. The extruding 

lavas were so viscous that they accumulated 

at the surface as thick, pasty blobs, or lava 

domes. After about 30,000 years, these rhyolites were followed by more voluminous eruptions of andesite and dacite, lavas lower in 

silica and higher in magnesium and iron than 

the earlier rhyolites. Forming much larger 

domes, the andesites and dacites are darker in 

color than the rhyolite, typically medium to 

dark gray, contain abundant large crystals, and 

are commonly oxidized (rusted) to brick red. 

The andesite-dacites erupted through 

numerous vents distributed throughout the 

castellated core. In addition to the magma that 

erupted at the surface, much andesite-dacite 

magma lodged below the ground as intrusive 

bodies, spreading and lifting the preexisting 

sedimentary layers. In this way, originally horizontal sedimentary layers around the perimeter of the volcano were bent upward to vertical 

and in some places overturned. This deformation is best displayed in the south moat of the 

volcano (see cross-section and map). 

The eruption of voluminous andesite-dacite 

continued until about 1.4 million years ago, 

creating the mountainous interior of the Sutter Buttes. Eruptions of volcanic domes were 

at times explosive because of an abundance 

of gases (mostly water vapor, carbon dioxide, and sulfur gases) in the magmas. The 

explosive eruptions fractured the dome rocks 

into fragments ranging from fine ash to giant 

blocks. These pyroclastic materials were carried downslope from the domes as slurries of 

debris made fluid by either hot volcanic gases 

(pyroclastic flows) or liquid water (lahars). 

The very hot pyroclastic flows and the cooler 

lahars accumulated around the base of the 

castellated core in layer after layer of debris, 

forming the gently outward-sloping rampart, 

a continuous debris apron or “fan” all the way 

around the castellated core of volcanic domes 

and over the truncated top of the surrounding 

moat sediments. 

The lowermost, rhyolitic layers of the 

rampart are exposed in only a few areas on 

the outer part of the moat valleys. These 

rhyolitic pyroclastic deposits are overlain by 

thick deposits derived from andesitic-dacitic 

pyroclastic flows and lahars. The uppermost 

layers of the rampart contain the largest blocks 

(about 30 feet in diameter), derived from the 

youngest, tallest, and best preserved domes of 

the core (South, North, West, Williams, Curtis, 

and Twin Peaks). 

Lakebeds

In the very center of the castellated core are 

the remnant deposits of a very deep lake that 

was formed during the volcanic eruptions of 

the Sutter Buttes. These layered deposits are 

mostly sands and gravels of andesite-dacite 

composition and are at least 1,000 feet thick. 

The lake may simply have filled a basin confined by volcanic domes, or the lake basin may 

have been excavated by powerful explosions 

during the andesite-dacite eruptive period. Today the lakebeds are surrounded and truncated 

by andesite-dacite domes that intruded into the 

layers and gently deformed and uplifted them 

to form a high central ridge in the Buttes.

Today’s Topography

At the end of volcanism about 1.4 million 

years ago, the castellated core and the rampart 

looked much as they do today. The castellated core was dominated by the youngest, 

tallest andesite-dacite domes. The rampart 

was a thick accumulation of pyroclastic-flow 

and lahar deposits. Over the past 1.4 million 

years, however, the erosional effects of rain, 

running water, and wind have cut down into 

the softest and weakest of the geologic materials of the Buttes. Streams and landslides have 

preferentially cut into the relatively weak shale 

and sandstone sedimentary layers to carve the 

moat valleys. Outward-flowing streams have 

also cut down through the pyroclastic debris 

layers to form distinctive radial valleys in the 

rampart. However, the elevations of the hard 

volcanic domes have probably not been lowered much by erosion. 

How Did the Buttes Get There?

An important question is whether the Sutter Buttes are related to the Cascade Range, 

which extends from the volcanoes of southern 

British Columbia to Lassen Peak in northern 

California, or to the Coast Range volcanic 

The sloping outer “rampart” of the Sutter Buttes 

was built by both volcanic mudflows (lahars) and 

hot flows of volcanic material (pyroclastic flows) 

that included large blocks, pictured here with a geologist (U.S. Geological Survey retired volcanolgist 

Robert L. Smith) for scale.

This aerial view looking east shows the low-lying “moat” between the high volcanic core of the Sutter Buttes and the sloping apron of the “rampart.” The moat was formed by erosion 

of soft sedimentary layers pushed up and tilted by the volcanic intrusions. Inset photograph at left shows 

North Butte, a high and well-preserved dacite dome in the central “castellated core” of the Sutter Buttes.
Thamer, D.H., 1961, Marysville Buttes, in 

Garrison, L.E., ed., Annual field trip, eastcentral Sacramento Valley–Marysville 

(Sutter) Buttes–Chico Creek–Oroville: 

Geological Society of Sacramento, 

p. 36-41, map scale 1:48,000.

Williams, H., 1929, Geology of the Marysville

 Buttes, California: University of California

 Publications in Geological Sciences, v. 18,

 p. 103–221. 

Williams, H., and Curtis, G.H., 1977, The

 Sutter Buttes of California; a study of Plio-

 Pleistocene volcanism: Berkeley, Univer-

 sity of California Press, 56 p. 

Brian P. Hausback1

, L.J. Patrick Muffler2,

and 

Michael A. Clynne2

Edited by Peter H. Stauffer

Graphic design by Judy Weathers

1

California State University, Sacramento

2

U.S. Geological Survey, Menlo Park, Calif.

COOPERATING ORGANIZATION

Middle Mountain Foundation—The Sutter 

Buttes Regional Land Trust

For more information contact:

Middle Mountain Foundation

P.O. Box 3359

Yuba City, CA 95992-3359 

(530) 755-3568

http://middlemountain.org, 

middlemountain@yahoo.com

For hike reservations, contact (530) 671-6116 

or 

mmfhikes@yahoo.com

trend, which includes the Berkeley Hills volcanics, the Sonoma Volcanics, and the Clear 

Lake Volcanics (the youngest of these, with 

eruptions from 2.1 million years to 10,000 

years ago). The Sutter Buttes do not fall on 

the geographic trend of either the Cascades or 

the Coast Range. However, the composition, 

texture, and age of the volcanic rocks suggest 

that the magmas that formed the Buttes are 

most likely part of the magmatic system of the 

Coast Range volcanoes. 

But why did eruptions occur at this isolated location in the middle of the Sacramento 

Valley, far from other volcanoes? Geophysical studies have revealed a prominent northsouth linear “ridge” that has anomalously 

high magnetism and gravity deep beneath 

the Sacramento Valley and directly under the 

Sutter Buttes. These geophysical features 

may be the expression of a buried, inactive 

fault that separates granitic and metamorphic rocks of the Sierra Nevada to the east 

from oceanic rocks of the Coast Range to 

the west. Additional faults intersect this deep 

crustal fault to provide possible conduits for 

Sutter Buttes magmas to rise to the surface. 

The Sutter Buttes contain the only lavas 

to erupt at the surface in the Great Valley, 

but rhyolites similar to those at the Buttes 

are found in the subsurface just to the west, 

along the Willows Fault. 

The Sutter Buttes stand as a remarkable 

geographic and geologic feature of California’s Great Valley, and they remain a subject 

of scientific interest and research. One curious 

feature is the presence at the surface in the castellated core of a huge block, one-quarter mile 

across, of crystalline rock (Cretaceous granite) 

characteristic of the Sierran basement. How 

was this block carried upward to the surface? 

Or is it perhaps the tip of an upfaulted sliver of 

the basement deep below? This is one of many 

puzzles remaining for geologists to solve in 

future studies.

Selected References

Cady, J., 1975, Magnetic and gravity anoma-

 lies in the Great Valley and western Sierra 

 Nevada metamorphic belt, California: 

 Geological Society of America Special 

 Paper 168, 56 p.

Dana, J.D., 1849, Notes on Upper California: 

American Journal of Science, Article 

XXV, series 2, v. 7, p. 247–264.

Dickinson, W.R., 1997, Tectonic implications of Cenozoic volcanism in coastal 

California: Geological Society of America 

Bulletin, v. 109, no. 8, p. 936–954.

Hausback, B.P., and Nilsen, T.H., 1999, Sutter 

Buttes, in Wagner, D.L., and Graham, S.A., 

eds., Geologic field trips in northern California: California Division of Mines and Geology Special Publication 119, p. 246–254.

For thousands of years, natural gas (largely methane) has leaked to the surface within and around the Sutter Buttes. Sometimes wildfires ignited these gas seeps, causing them to produce eerie blue flames that 

emerged from cracks in the ground and continued to burn long after the wildfires were quenched by rain. This 

phenomenon undoubtedly provoked a sense of awe and reverence for these dramatic crags located in the 

middle of a broad, flat valley. The native Maidu people named the Buttes “Histum Yani” or Middle Mountain.

Unlike the San Joaquin Valley (the southern part of California’s Great Valley), the Sacramento Valley to the 

north has no appreciable deposits of oil, but it does have much natural gas. This gas was generated from 

microscopic plankton that died and sank to the ancient sea floor to be entombed in marine mud. Gradual 

burial by as much as 38,000 feet of overlying sediments created high temperatures and pressures that 

transformed the organic remains into gas. The volcanic upheaval that formed the Sutter Buttes pushed 

some of these sediments upwards, creating natural traps for methane and other gases rising from depth.

Exploration for gas in the Sutter Buttes area began in 1864, when a local worker and entrepreneur, Dexter 

Cook, sank a shaft near South Butte. The 30-foot-deep shaft filled with gas and inevitably exploded when he lit 

a candle at the bottom, injuring four men. The shaft was deepened to 65 feet and then sealed, leaving a pipe extending above the surface. The gas streamed out and for years produced a 5-foot-tall, blue, smokeless flame. 

The first commercial natural-gas well in the Sacramento Valley was completed to a depth of 2,727 feet in the southwestern moat of the Sutter Buttes in early 1933. 

This “discovery well” flowed at 3.4 million cubic feet of gas per day and still produces today, along with many other modern wells. Gas from the wells is collected 

into pipelines and distributed throughout northern California.

NATURAL GAS IN THE SUTTER BUTTES

Within the castellated core, layered lake-bed deposits, more than 1,000 feet thick, attest to the former 

existence of a lake in the center of Sutter Buttes.

This discovery well at Sutter Buttes still produces gas.