Editing Mount Hood (section)

==Volcanic activity==
[[File:Mount Hood, Oregon.jpg|thumb|[[Satellite imagery|Satellite image]] of Mount Hood]]
The glacially eroded summit area consists of several [[andesitic]] or [[dacitic]] [[lava dome]]s; [[Pleistocene]] collapses produced avalanches and [[lahar]]s (rapidly moving mudflows) that traveled across the [[Columbia River]] to the north. The eroded volcano has had at least four major eruptive periods during the past 15,000 years.<ref name=volcanoinformation>{{cite web |url=http://volcanoes.usgs.gov/about/volcanoes/cascades/mounthood.php |title=Volcano Information: Mount Hood |publisher=U.S. Geological Survey |date=2008-06-02 |access-date=2013-07-18 |archive-date=2013-02-22 |archive-url=https://web.archive.org/web/20130222191000/http://volcanoes.usgs.gov/about/volcanoes/cascades/mounthood.php |url-status=live}}<br> {{PD-notice}}</ref>

The last three eruptions at Mount Hood occurred within the past 1,800 years from vents high on the southwest flank and produced deposits that were distributed primarily to the south and west along the [[Sandy River (Oregon)|Sandy]] and [[Zigzag River|Zigzag]] rivers. The volcano has had a [[VEI]] of 2 at least three times before.<ref>{{cite web|url=https://volcano.si.edu/volcano.cfm?vn=322010|title=Global Volcanism Program &#124; Hood|website=Smithsonian Institution &#124; Global Volcanism Program|access-date=2024-09-18}}</ref> The last eruptive period took place around 220 to 170 years ago, when dacitic lava domes, pyroclastic flows and mudflows were produced without major explosive eruptions. The prominent Crater Rock just below the summit is hypothesized to be the remains of one of these now-eroded domes. This period includes the last major eruption of 1781 to 1782 with a slightly more recent episode ending shortly before the arrival of the explorers [[Lewis and Clark Expedition|Lewis and Clark]] in 1805. The latest minor eruptive event was thought to have occurred in August 1907,<ref name=volcanoinformation/><ref name="vulcan_hood">{{cite journal |title=Recent Eruptive History of Mount Hood, Oregon, and Potential Hazards from Future Eruptions |first=Dwight R. |last=Crandell |journal=Geological Survey Bulletin |issue=1492 |url=https://pubs.er.usgs.gov/publication/b1492 |publisher=U.S. Geological Survey |year=1980 |pages=1, 7–8, 43–45 |doi=10.3133/b1492| access-date=2013-07-13| archive-date=2012-09-22| archive-url=https://web.archive.org/web/20120922065002/http://pubs.er.usgs.gov/publication/b1492| url-status=live|doi-access=free }}</ref> but has been discredited as "an observation of non-eruptive fumarolic activity."
<ref name="eruptive_history">{{cite journal |journal=Smithsonian Institution National Museum of Natural History Global Volcanism Program |title=Mount Hood: Eruptive History |url=https://volcano.si.edu/volcano.cfm?vn=322010}}</ref>

The glaciers on the mountain's upper slopes may be a source of potentially dangerous lahars when the mountain next erupts. There are vents near the summit that are known for emitting gases such as [[carbon dioxide]] and [[sulfur dioxide]].<ref name=lavadomes>{{cite web |url=http://vulcan.wr.usgs.gov/Volcanoes/Hood/Publications/EV24-6/dome_collapse_hood.html |title=The Danger of Collapsing Lava Domes: Lessons for Mount Hood, Oregon |work=Earthquakes & Volcanoes, v. 24, n. 6, pp. 244–269 |first1=Steven R. |last1=Brantley |first2=William E. |last2=Scott |publisher=U.S. Geological Survey |access-date=2013-07-18 |archive-date=2013-06-22 |archive-url=https://web.archive.org/web/20130622132813/http://vulcan.wr.usgs.gov/Volcanoes/Hood/Publications/EV24-6/dome_collapse_hood.html |url-status=live}}</ref> Prior to the [[1980 eruption of Mount St. Helens]], the only known fatality related to volcanic activity in the Cascades occurred in 1934, when a climber suffocated in oxygen-poor air while exploring ice caves melted by [[fumarole]]s in [[Coalman Glacier]] on Mount Hood.<ref name="Swanson"/>

Since 1950, there have been several [[earthquake swarm]]s each year at Mount Hood, most notably in July 1980 and June 2002.<ref>{{cite gvp |vn=322010 |vtab=Latest |title=Hood: Latest Activity Reports| access-date=2007-06-22}}</ref><ref>{{cite web |url=http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/2002/current_updates_20020629.html |title=Cascade Range Current Update for June 29, 2002 |publisher=U.S. Geological Survey |date=2002-06-29| archive-url=https://web.archive.org/web/20130904065938/http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/2002/current_updates_20020629.html| archive-date=2013-09-04}}</ref>
Seismic activity is monitored by the USGS [[Cascades Volcano Observatory]] in [[Vancouver, Washington]], which issues weekly updates (and daily updates if significant eruptive activity is occurring at a Cascades volcano).<ref>{{cite web |title=Current Alerts for U.S. Volcanoes: Cascade Range Volcanoes |url=http://volcanoes.usgs.gov/activity/status.php#cvo |publisher=U.S. Geological Survey| access-date=2013-07-13| archive-date=2013-07-28| archive-url=https://web.archive.org/web/20130728161134/http://volcanoes.usgs.gov/activity/status.php#cvo| url-status=live}}</ref>

The most recent evidence of volcanic activity at Mount Hood consists of fumaroles near Crater Rock and [[hot springs]] on the flanks of the volcano.<ref name="DONF">{{cite web |url=http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/hood.shtml| archive-url=https://web.archive.org/web/20110512011355/http://www.fs.fed.us/r6/centraloregon/geology/info/volcanoes/hood.shtml| archive-date=2011-05-12 |title=Oregon Volcanoes: Mt. Hood Volcano |publisher=U.S. Forest Service |date=2003-12-24}}</ref>

===Monitoring controversy===
[[File:Mount Hood monitoring station.jpg|thumb|New seismic/GPS station (LSON) installed at Mount Hood]]
[[File:Installation-gps-mast-station-brsp-mount-hood.jpg|thumb|Installation of GPS mast at station BRSP on Mount Hood]]
[[File:Mount Hood air delivery.jpg|thumb|A helicopter delivers equipment to station BRSP on Mount Hood.]]
A conflict exists between protecting public safety and protecting the environment. In 2014, a [[USGS]] employee, Dr. Seth Moran, proposed installing new instruments on Mount Hood to warn of volcanic activity. The instruments were installed at four different locations on the mountain, including:
*three seismometers to measure earthquakes
*three [[Global Positioning System]] (GPS) instruments to measure ground movement
*one instrument to measure gas emissions
The proposed locations were in a protected wilderness area, tightly controlled by the [[United States Forest Service]]. The project was opposed by Wilderness Watch, a conservation group.<ref>{{cite news |title=We're Barely Listening to the U.S.'s Most Dangerous Volcanoes—A thicket of red tape and regulations have made it difficult for volcanologists to build monitoring stations along Mount Hood and other active volcanoes.  |author=Shannon Hall |date=September 9, 2019 |work=[[The New York Times]] |url=https://www.nytimes.com/2019/09/09/science/volcanoes-cascades-monitoring.html |access-date=January 2, 2023}}</ref>

Three monitoring stations were eventually installed on Mount Hood in 2020.<ref>{{cite news |title=Three new monitoring stations installed at Mount Hood |date=November 13, 2020 |url=https://www.usgs.gov/news/three-new-monitoring-stations-installed-mount-hood |access-date=January 2, 2023}}</ref>