Tumalo Mountain is a shield volcano

Shield volcano

A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...

 in the Cascade Range

Cascade Range

The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...

 of central Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

, located just northeast of Mount Bachelor

Mount Bachelor

Mount Bachelor, formerly named Bachelor Butte, is a stratovolcano atop a shield volcano in the Cascade Volcanic Arc and the Cascade Range of central Oregon.The Mount Bachelor ski area has operated on the mountain since 1958....

 across the Cascade Lakes Scenic Byway

Cascade Lakes Scenic Byway

The Cascades Lakes Scenic Byway is a National Scenic Byway in central Oregon in the United States. It runs for in the rugged country of Deschutes and Klamath counties on the east side of the Cascade Range. It offers particularly good views of Mount Bachelor and provides access to many...

. Ice Age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 glaciers carved a large cirque

Cirque (landform)

thumb|250 px|Two cirques with semi-permanent snowpatches in [[Abisko National Park]], [[Sweden]].A cirque or corrie is an amphitheatre-like valley head, formed at the head of a valley glacier by erosion...

 into the northeast flank of the mountain, producing a bowl which is popular with local backcountry skiers. A United States Forest Service

United States Forest Service

The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...

 fire lookout tower

Fire lookout tower

A fire lookout tower, fire tower or lookout tower, provides housing and protection for a person known as a "fire lookout" whose duty it is to search for wildfires in the wilderness...

was built on the summit in the 1930s, but abandoned in the 1970s and subsequently removed. A trail to the summit ascends the southwest flank of the volcano.