Mammoth Mountain

Lava dome(s) in United States

Last Eruption: 1260

Key Facts

Elevation

3,369 m (11,053 ft)

Type

Lava dome(s)

Location

37.631°, -119.032°

Region

Basin and Range Volcanic Province

Rock Type

Trachyte / Trachydacite

Tectonic Setting

Rift zone

Location

Loading map...

Overview

Mammoth Mountain, a trachydacitic lava-dome complex, lies on the SW topographic rim of Long Valley caldera. It is west of the structural rim of the caldera and considered to represent a magmatic system distinct from other nearby volcanic regions (Hildreth, 2004). The latest magmatic eruptions took place about 57,000 years ago.

Mammoth Mountain is surrounded by at least 35 mafic vents that are part of the same magmatic system and include Red Cones, two closely spaced basaltic cinder cones SW of Mammoth Mountain and SE of Devils Postpile National Monument. The cones, whose name derives from colorful scoria deposits, are unglaciated and were radiocarbon dated at about 8,500 years ago. Phreatic eruptions, distinct from those at South Inyo Craters, took place about 700 years ago from vents on the north side of Mammoth Mountain.

Recent unrest, including seismicity, gas emission, and tree kill, is thought to be related to dike intrusion in 1989.

Volcanic Hazards & Risk Assessment

Primary Hazards

Risk Level

Population at RiskModerate

Infrastructure RiskModerate

Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary

Trachyte / Trachydacite

Silica Content

Varied composition

Tectonic Setting

Rift zone

Continental rift or intraplate setting with varied eruptive styles.

Age & Formation

Epoch

Holocene

Evidence

Eruption Dated

Eruption Statistics & Analysis

Metric	Value	Global Ranking	Significance
Total Recorded Eruptions	Unknown	Low	Moderately active volcano
Maximum VEI	VEI Unknown	Minor	Local impact potential
Recent Activity	766 years ago	Historical	Historically active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program

International eruption database

Current Status

Normal

No recent activity. Routine monitoring continues.

Nearby Volcanoes in North America Volcanic Regions

Regional Volcanic Activity

The North America Volcanic Regions contains multiple active volcanic systems. Cross-regional magma interactions and tectonic stresses can influence eruption patterns across the entire arc. Monitor regional seismic activity and volcanic alerts.

Quick Info

•Smithsonian ID: 323150
•Evidence: Eruption Dated
•Epoch: Holocene

About the Photo

Mammoth Mountain, a Pleistocene trachydacitic lava-dome complex constructed on the SW topographic rim of the Long Valley caldera between about 200,000 and 50,000 years ago, forms the broad peak on the horizon. The Red Cones (center and lower left) are part of series of about three dozen mafic cones surrounding Mammoth Mountain. The oxidized reddish scoria of the cone, which was formed during the early Holocene, is mantled at its base by light-colored pumice erupted from the Inyo Craters about 650 years ago.

Photo by Lee Siebert, 1998 (Smithsonian Institution)