Cascade Volcanoes and Cascadia Subduction Zone

clipclop said:

There doesn't appear to be a lot of current info on activity of the Garibaldi volcanic complex in Canada.

1oldman2 said:

http://volcano.si.edu/volcano.cfm?vn=320200

clipclop said:

There doesn't appear to be a lot of current info on activity of the Garibaldi volcanic complex in Canada.

Astronuc said:

There does seem to be a lack of information on the Garibaldi Volcanic Complex.

There is a Wikipedia article, which describes the Garibaldi Volcanic Belt as a continuation of the Cascades.
https://en.wikipedia.org/wiki/Garibaldi_Volcanic_Belt

https://en.wikipedia.org/wiki/Garibaldi_Volcanic_Belt#Geothermal_and_seismic_activity
According to that section, "at least four volcanoes have had seismic activity since 1985, including Mount Garibaldi (three events), Mount Cayley (four events), Mount Meager (seventeen events) and the Silverthrone Caldera (two events). Seismic data suggest that these volcanoes still contain active magma chambers, indicating that some Garibaldi Belt volcanoes are likely active, with significant potential hazards."
One of the references seems to no longer exist, but it is available on the Wayback Archive - http://wayback.archive.org/web/20061008200258/http://gsc.nrcan.gc.ca/volcanoes/gscvol_e.php

I looked at the Natural Resources Canada website, but only found Earth Sciences - https://www.nrcan.gc.ca/earth-sciences
https://www.nrcan.gc.ca/earth-sciences/resources/publications

It seems that they have reduced the program on volcanoes - http://chis.nrcan.gc.ca/volcano-volcan/index-en.php

Earthquakes has a bit more - http://www.earthquakescanada.nrcan.gc.ca/index-en.php

It might be worthwhile for those in Canada to contact the institution and see if they would reinstate the volcanoes portion of the site.
Geological Survey of Canada, Strategic Plan 2013-2018
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=293638

The composition of the molten rock (magma) that feeds volcanism in the Lassen area ranges widely in its content of silica (SiO2). When high-silica (dacite) magma rises to the Earth’s surface, it can erupt explosively to produce ash clouds and pyroclastic flows. Dacite magma extruded nonexplosively forms lava domes, because it is too viscous to flow far away from its source. Low-silica (basalt) magma is more fluid and usually erupts less explosively than dacite magma. Eruptions of basalt magma typically produce elongate lava flows, as well as build cinder cones (piles of small frothy lava fragments or “cinders”) around volcanic vents.

In the past 50,000 years, at least seven major episodes of dacitic volcanism produced lava domes and pyroclastic deposits in the Lassen area, and another five episodes produced basaltic and andesitic (silica content between basalt and dacite) lava flows. In addition, about 30 smaller volcanoes erupted basaltic lavas in the larger region surrounding the Lassen volcanic center.

Astronuc said:

There is an active monitoring program at Mt. Rainier and at Mt. St. Helens. I don't know much about the other volcanoes.

wikipedia said:

Seismic activity around Adams is very low and it is one of the quietest volcanoes in Oregon and Washington. It is monitored by the Pacific Northwest Seismic Network and the Cascades Volcano Observatory via a seismic station on the southwest flank of the mountain.

Mark44 said:

I have some familiarity with the five Washington volcanoes, having climbed all of them, in addition to Hood in Oregon, and Shasta and Lassen in California....

M 4.7 - 160 km W of Langlois, Oregon​

• 2021-10-24 12:11:40 (UTC)
• 43.179°N 126.395°W
• 10.0 km depth

Mount St. Helens sits oddly apart from the other Cascade Volcanoes.

iMUSH is a four year collaborative research project involving several institutions and supported by the GeoPRISMS and EarthScope Programs of the US National Science Foundation to illuminate the architecture of the greater Mount St. Helens magmatic system from slab to surface.

A Large Landslide Occurred at Mount Saint Helens; Major Road Closed (May 14, 2023)​

On Sunday evening, May 14, 2023, around 9 p.m. a saturated deposit of material from the 1980 volcanic eruption of Mount St. Helens gave rise to a gravity-driven debris flow that released thousands of tons of debris into South Coldwater Creek.

The debris flow, referred to as the South Coldwater Slide, caused significant damage to the upper portion of State Route (SR) 504 near milepost 49 leading up to the Johnston Ridge Observatory north of Mount St. Helens. The event followed a recent warming trend and significant snowmelt that had saturated the ground. The debris flow washed out the Spirit Lake Outlet Bridge, an 85-foot structure, damaged the roadway, and severed power to Johnston Ridge Observatory.

What we've learned since 1980.​

1982 - Burlington Northern Inc. will donate its holdings on the Mount St. Helens volcano, more than 690 acres which include a portion of the crater, to the U.S. government for use as a national volcanic park, the White House announced Tuesday.

The transportation and natural resources company headquartered in Seattle has owned the sections since 1970 when it acquired the land in a merger. It was not immediately determined if the company would be able to take a tax deduction for the donated land, which was once prime timberland.

The territory being turned over to the government includes a square mile on top of the mountain and the 50 acres on nearby Spirit Lake that was once the home of 83-year-old Harry Truman, the colorful lodge operator who refused to leave his home and is believed to have died in the eruptions.

The land and other sections originally were part of federal land grants issued in 1864 to the Northern Pacific Railroad as a way to raise money to build a transcontinental rail network. The merger of the Northern Pacific with two other lines in 1970 created Burlington Northern.

About one-third of the Burlington Northern acreage was destroyed by the eruption.