Simcoe Mountains
| Simcoe Mountains | |
|---|---|
| location | Klickitat County / Yakima County , Washington , USA |
| Coordinates | 45 ° 59 ′ N , 120 ° 43 ′ W |
The Simcoe Mountains (or the Simcoe Mountains Volcanic Field ) is a group of lava flows and extinct volcanoes in the southern central part of Washington state , east of Mount Adams . The northern and central parts of the Simcoe Mountains are within the Yakama Indian Reservation . Although the volcanic field is close to the cascade volcanoes , it is a much older volcanic field that is not related to mountain formation (anorogenic); it is therefore not counted among the cascade volcanoes.
Highest peaks
Map with all coordinates of the section Highest peaks : OSM
Most volcanic vents rise 75 ... 250 meters above the area, with the exception of Signal Peak, which towers above the area by 500 meters. The highest peaks in the Simcoe Mountains are:
- Jennie Butte (6,404 ft (1,952 m)), a dacite - cone - 46 ° 24 ' N , 121 ° 19' W
- Indian Rock (5,820 ft (1,774 m)), a basaltic shield volcano - 45 ° 59 ′ N , 120 ° 50 ′ W
- Castle Rock (4,987 ft (1,520 m)), a Basdaltic shield volcano - 46 ° 2 ′ N , 120 ° 49 ′ W
- Signal Peak (5,102 ft (1,555 m)), a 5.7 million year old mafic shield volcano - 46 ° 14 ′ N , 121 ° 8 ′ W
geology
The Simcoe Mountains lie in the Yakima Fold Belt within the Columbia River Basalt Group . The eruptions of the now extinct volcanoes occurred in three periods during the Pliocene and Quaternary ; the first period lasted from 4.2… 3.2 million years BP , the second period from 2.2… 1.2 million years BP and the most recent period from 1.0… 0.6 million years BP. The most recent eruption is a trachybasaltic lava flow from 631,000 ± 27,000 years ago, the so-called "Trachybasalt of Pretty Swamp".
Some of the volcanic activity in the Simcoe Mountains occurred at the same time as eruptions in the Goat Rocks to the northwest. For the past 350,000 years that the Simcoe Mountains volcanoes were active, there was also activity in the Mount Adams region , but Mount Adams itself had not yet formed. Indian Heaven , a volcanic field further west, is also much younger than the Simcoe Mountains. Only the oldest 200,000 years of activity in Indian Heaven overlap with the most recent 200,000 years of activity in the Simcoe Mountains. The Mount St. Helens as well as the Mount Adams fully emerged after the Simcoe Mountains.
See also
Individual evidence
- ^ A b c d Wes Fierstein, Judy Hildreth: USGS Scientific Investigations Map 3315: Geologic Map of the Simcoe Mountains Volcanic Field, Main Central Segment, Yakama Nation, Washington .
- ↑ Jennies Butte ( English ) In: Geographic Names Information System . United States Geological Survey . Retrieved February 1, 2019.
- ↑ Indian Rock ( English ) In: Geographic Names Information System . United States Geological Survey . Retrieved February 1, 2019.
- ↑ Castle Rock ( English ) In: Geographic Names Information System . United States Geological Survey . Retrieved February 1, 2019.
- ↑ Signal Peak ( English ) In: Geographic Names Information System . United States Geological Survey . Retrieved February 1, 2019.
Web links
- Simcoe Mountains ( English ) In: Geographic Names Information System . United States Geological Survey . Retrieved February 1, 2019.