U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004--3044

April 2004

Prepared in cooperation with the Pyramid Lake Paiute Tribe and the Pyramid Lake Museum Visitor Center

The Tufas of Pyramid Lake, Nevada

Printed on recycled paper

Figure 1. Pyramid Island along the east shore of 

Pyramid Lake. 

Figure 2. Pluvial Lake Lahontan at its highstand 

about 15,000 years ago. The black areas indicate 

perennial lakes that exist today. The gray areas 

indicate ephemeral lakes and sinks. The blue area 

indicates the surface area of Lake Lahontan at its 

highstand. The red lines indicate overflow points 

(sills) between subbasins. Sill elevations: Darwin 

Pass (1,265 m), Mud Lake (1,177 m), Astor Pass 

(1,222 m), and Emerson Pass (1,207 m).

Figure 3. Dense tufa coating 

volcanic cobbles in the Terraced 

Hills area at the north end of 

Pyramid Lake.

Figure 4. Thinolite crystals exposed at 

the base of the Blanc Tetons site.

BACKGROUND

Pyramid Lake is the site of some of 

the Earth’s most spectacular tufa deposits. Tufa is a rock composed of calcium 

carbonate (CaCO3) that forms at the 

mouth of a spring, from lake water, or 

from a mixture of spring and lake water. 

The explorer John C. Fremont (1845) 

wrote about the tufas during his 1843-

44 expedition and named the lake after 

the pyramidal-shaped island that lies 

along the east shore of the lake (fig. 1). 

The Paiute name for the island is Wono, 

meaning cone-shaped basket. The Paiute 

name for the lake is Cui-Ui Panunadu, 

meaning fish in standing water. 

The U.S. Geological Survey, in cooperation with the Pyramid Lake Paiute 

Tribe, has obtained radiocarbon ages 

of many of the tufa deposits that border 

Pyramid Lake in order to obtain a record 

of lake level change for the past 35,000 

years (Benson, 1994). 

THE FORMATION OF TUFAS

Most of the tufas formed between 

26,000 and 13,000 years ago when the 

climate was much wetter, and Pyramid 

Lake was joined to lakes in nearby subbasins. Pluvial lakes, such as Lake Lahontan, formed during this wetter climate. 

These lakes are transitional in nature, 

and today, many are 

gone or exist only as 

remnants. Pyramid 

Lake is one of seven 

water bodies that 

coalesced to form 

pluvial Lake Lahontan (fig. 2). At its 

highstand, Lake 

Lahontan was 281 m 

deep (compared to 

106 m in 2004) and covered 22,800 km2, 

a surface area slightly larger than presentday Lake Ontario. 

Tufas in the Pyramid Lake subbasin 

were first mentioned in scientific literature by Fremont (1845), who erroneously 

believed they had formed above water. 

Tufa mounds formed when springs 

discharged from the bottom of Pyramid 

Lake, supplying calcium that combined 

with carbonate dissolved in lake water 

to form the mounds. The thickest tufa 

deposits formed near lake-bottom sites of 

ground-water discharge, and at overflow 

elevations where the lake was held at 

near-constant levels for long periods of 

time. 

TUFA VARIETIES AND FORMS

Russell (1885) was the first to suggest that there were three tufa varieties, 

including lithoid (dense), thinolitic (crystalline) and dendritic (branching) (figs. 

3, 4, 5). Two other varieties have been 

noted in the Pyramid Lake area: a finegrained carbonate that cements sand and 

gravel forming beachrock (fig. 6), and a 

thin white porous carbonate that coats the 

outer surfaces of older tufas (fig. 7). 

 Tufa varieties combine to become tufa 

forms. Common forms include: (1) tufa 

pillows (fig. 8), composed of branching 

tufa and dense tufa nodules (fig. 5); (2) 

tufa tubes, composed of dense or branching varieties of tufa that sometime surround a thinolitic crystal mesh 

(fig. 4); (3) tufa sheets and 

drapes, which are primarily 

composed of branching tufa; 

and (4) tufa spheres or barrels, 

commonly composed of one 

or more layers of thinolitic crystals. In 

some situations, tufa forms combine 

to create tufa megaforms, such as tufa 

mounds (fig.7) and tufa reefs (figs. 8, 9). 

The largest collection of mounds occurs 

at the north end of Pyramid Lake at the 

Needles Rocks site. The locations of 

tufas depicted in this fact sheet are shown 

in Figure 10. 
For more information, contact:

Chief, Branch of Regional Research

U.S. Geological Survey, MS 418

Denver Federal Center, Box 25046

Denver, CO 80225-0046

Figure 6. Layers of 

beachrock adjacent to and 

north of Indian Head Rock.

Figure 7. The southern Blanc 

Tetons mound. Large tufa 

spheroids have been coated 

and cemented with white 

porous tufa. 

Figure 8. Tufa 

pillows making up 

a reef-like tufa on 

Anaho Island.

Figure 9. Tufa reefs coating Marble Bluff.

Figure 10. Locations of tufa sites discussed in 

this fact sheet.

Figure 5. Tufa pillows at 

Doghead Rock composed of 

branching tufa (B) and dense (D) 

tufa pendants and nodules.

THE ELEVATION OF TUFA 

DEPOSITS AND THEIR RELATION 

TO OVERFLOW POINTS (SILLS)

Because tufas form in lake water, 

it follows that their vertical growth is 

limited by lake level. In 

the Pyramid Lake subbasin, 

the elevations of the tops of 

many tufa mounds correspond to elevations of intersubbasin overflow points, or 

sills (fig. 2). When the level of Pyramid 

Lake was held constant by overflow to 

an adjacent subbasin, erosion of tufa and 

sediment occurred at and slightly above 

the overflow level, and deposition of 

tufa occurred below the overflow level. 

Terraces were created by both erosional 

and constructional processes. In addition, many other reef-like tufa deposits 

formed on rocky headland areas when the 

level of Pyramid Lake was kept relatively 

constant by overflow to adjacent lake 

subbasins. 

Many of the tufas illustrated in this 

and other reports (Benson, 1994; Benson, 

2004) have been dated using the radiocarbon method (Benson and others, 1995). 

The elevations and ages of the tufa allow 

us to construct a lake-level history for the 

last 35,000 years. The data indicate that 

Lake Lahontan rose sharply about 26,000 

years ago and was maintained at about 

1,265 m for the next 7,000 years by overflow to the Carson Desert. After a brief 

fall to less than 1,250 m, Lake Lahontan 

rose rapidly to its highstand (1,335 m) 

about 15,000 years ago 

and then fell rapidly 

between 14,000 and 

13,000 years ago. 

RECENT TUFA FORMATION

Deposition of tufa megaforms appears 

to have ended with the fall of Lake 

Lahontan between 14,000 and 13,000 

years ago. We do not know why tufa 

deposition essentially ceased; however, 

decreases in the discharge of lake-bottom springs may have sharply lessened 

the amount of calcium available for tufa 

precipitation. Accurate dates for recent 

encrusting varieties of tufa are not available, in part because it is not known how 

much “old” carbon was introduced into 

the tufas by ground-water sources during 

their precipitation (Benson and others 

1995). In addition, tufas re-exposed to 

lake water, either by a rise in lake level or 

by removal of the lake sediment that surrounds them, may acquire additional calcium carbonate. The Needles Rocks area 

has experienced continued discharge of 

calcium-bearing waters into the bases of 

the tufa mounds. This younger calcium 

carbonate fills preexisting pore spaces in 

the tufa or adds calcium carbonate to the 

outside of a tufa. Many of the bases of 

tufa mounds that surround Pyramid Lake 

have been cemented with younger tufa, as 

indicated by the presence of “girdles” of 

calcium carbonate. Existing data indicate 

that the level of Pyramid Lake did not 

exceed the elevation of Mud Lake Sill 

which ranged from 1,177 to 1,183 m during the past 8,000 years (Benson and others, 2002), suggesting that cementation of 

the old tufa mounds occurred during that 

time interval.

—Larry Benson 

REFERENCES

Benson, L.V., 1994, Carbonate deposition, Pyramid 

Lake subbasin, Nevada: 1. Sequence of formation and elevational distribution of carbonate 

deposits (tufas): Palaeogeography, Palaeoclimatology, Palaeoecology, v. 109, p. 55-87.

Benson, L.V., 2004, The tufas of Pyramid Lake, 

Nevada: U.S. Geological Survey Circular 1267, 

14 pp.

Benson, L.V., Kashgarian M., and Rubin, M., 1995, 

Carbonate deposition, Pyramid Lake subbasin, 

Nevada: 2. Lake levels and polar jet stream 

positions reconstructed from radiocarbon ages 

and elevations of carbonate deposits (tufas): 

Palaeogeography, Palaeoclimatology, 

Palaeoecology, v. 117, p. 1-30.

Benson, L., Kashgarian, M., Rye, R., Lund, S., 

Paillet, F., Smoot, J., Kester, C., Mensing, S., 

Meko, D., and Lindstrom, S., 2002, Holocene 

multidecadal and multicentennial droughts 

affecting northern California and Nevada: 

Quaternary Science Reviews v. 21, p. 659-682.

Fremont, J. C., 1845, Report of the exploring 

expedition to the Rocky Mountains in the year 

1843 and to Oregon and north California in the 

years 1843-44: Washington D.C.

Russell, I. C., 1885, Geological history of Lake 

Lahontan, a quaternary lake of northwestern 

Nevada: U. S. Geological Survey Monograph 11, 

287 pp.