| Dumbell Mountain | |
| Elevation Ft: | 8416 |
| Elevation Ref: | [1] |
| Prominence Ft: | 1316 |
| Isolation Mi: | 2.53 |
| Parent Peak: | Seven Fingered Jack |
| Map: | Washington#USA |
| Country: | United States |
| State: | Washington |
| Region: | Chelan |
| Region Type: | County |
| Part Type: | Protected area |
| Part: | Glacier Peak Wilderness |
| Range: | Entiat Mountains North Cascades Cascade Range |
| Coordinates: | 48.1801°N -120.8587°W |
| Topo: | USGS Holden |
| Rock: | Dumbell Mountain plutons gneissic hornblende quartz diorite |
| Age: | Cretaceous |
| First Ascent: | 1932 Richard Alt, George Fahey |
| Easiest Route: | Scrambling |
Dumbell Mountain is an 8416feet double summit massif located in the Glacier Peak Wilderness of the North Cascades, in Chelan County of Washington state. The Dumbell summit is slightly higher than the northeast subpeak (8,408 ft) which is unofficially called Greenwood Mountain. The nearest higher neighbor is Chiwawa Mountain, 2.4miles to the east-southeast. Precipitation runoff from Dumbell Mountain drains into tributaries of the Chelan River and the Wenatchee River. The mountain's descriptive name was applied by Albert Hale Sylvester (1871-1944), pioneer surveyor, explorer, topographer, and forest supervisor in the Cascades.
Dumbell Mountain is located in the Cloudy Pass batholith, an intrusive formation that was formed approximately, during the early Miocene.[2] [3] The history of the formation of the Cascade Mountains dates back millions of years ago to the late Eocene Epoch.[4] With the North American Plate overriding the Pacific Plate, episodes of volcanic igneous activity persisted.[4] In addition, small fragments of the oceanic and continental lithosphere called terranes created the North Cascades about 50 million years ago.[4] During the Pleistocene period dating back over two million years ago, glaciation advancing and retreating repeatedly scoured and shaped the landscape.[4] Glaciation was most prevalent approximately, and most valleys were ice-free by .[5] Uplift and faulting in combination with glaciation have been the dominant processes which have created the tall peaks and deep valleys of the North Cascades area.Subduction and tectonic activity in the area began during the late cretaceous period, about . Extensive volcanic activity began to take place in the oligocene, about .[6] Glacier Peak, a stratovolcano that is southwest of Dumbell Mountain, began forming in the mid-Pleistocene.[7]
Dumbell Mountain is located in the marine west coast climate zone of western North America.[8] Weather fronts coming off the Pacific Ocean travel northeast toward the Cascade Mountains. As fronts approach the North Cascades, they are forced upward by the peaks of the Cascade Range, causing them to drop their moisture in the form of rain or snow onto the Cascades (Orographic lift). As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.[9] Because of maritime influence, snow tends to be wet and heavy, resulting in high avalanche danger.[2] During winter months, weather is usually cloudy, but, due to high pressure systems over the Pacific Ocean that intensify during summer months, there is often little or no cloud cover during the summer.[2] Due to its temperate climate and proximity to the Pacific Ocean, areas west of the Cascade Crest very rarely experience temperatures below 0°F or above 80°F.[2]