USGS Cautions: Prepare NOW for Non-Imminent Eruption of Mauna Loa

[jedishrfu]

TL;DR

The U.S. Geological Survey (USGS) is urging people to prepare for the possibility of an eruption at the world’s largest volcano: Mauna Loa on the Big Island of Hawaii. In a recent news release, Hawaiian Volcano Observatory (HVO) scientists with USGS cautioned, “While an eruption of Mauna Loa is not imminent, now is the time to revisit personal eruption plans. Similar to preparing for hurricane season, having an eruption plan in advance helps during an emergency.”

Mauna Loa is considered the largest active volcano on Earth, rising to 13,681 feet above sea level. Mauna Loa rises up from the ocean floor of the Central Pacific at a depth of about 3 miles. Because of the volcano’s significant mass, the ocean floor directly beneath Mauna Loa is depressed by another 5 miles. According to USGS, this places Mauna Loa’s summit about 56,000 feet above its base; the enormous volcano covers half of the island of Hawaii, also known simply as the “Big Island of Hawaii.”

Mauna Loa eruptions tend to produce voluminous, fast-moving lava flows that can impact communities on the east and west sides of the Big Island from Kona to Hilo. Since the 1850s, Hilo in eastern Hawaii has been threatened by 7 Mauna Loa lava flows. On the south and west sides of the island, Mauna Loa lava flows have reached the coast there 8 times: in 1859, 1868, 1887, 1926, 1919, and three times in 1950.

https://weatherboy.com/usgs-cautions-that-the-worlds-largest-volcano-could-erupt/

 

[jedishrfu]

And the USGS publication:

https://www.usgs.gov/center-news/volcano-watch-failing-prepare-you-are-preparing-fail-benjamin-franklin

Volcano Watch — “By failing to prepare, you are preparing to fail.” – Benjamin Franklin
Release Date: MARCH 11, 2021
Mauna Loa has been in the news lately, as the volcano continues to awaken from its slumber. While an eruption of Mauna Loa is not imminent, now is the time to revisit personal eruption plans. Similar to preparing for hurricane season, having an eruption plan in advance helps during an emergency.

 

[Astronuc]

This morning, I was looking at the USGS world map a saw 4 earthquakes in Hawaii. Two were near the SE coast of the island Hawaii.

M 3.2 - 3 km S of Pāhala, Hawaii
https://earthquake.usgs.gov/earthquakes/eventpage/hv72386777/executive

• 2021-03-17 10:25:19 (UTC)
• 19.173°N 155.475°W
• 32.6 km depth

M 2.7 - 10 km E of Pāhala, Hawaii
https://earthquake.usgs.gov/earthquakes/eventpage/hv72386657/executive

• 2021-03-17 08:14:51 (UTC)
• 19.218°N 155.379°W
• 32.4 km depth

But there were two near the peak of Mauna Loa of the same magnitude, but they have since been removed/retracted. I was thinking that they may be clear signs of a pending eruption, but now the information disappeared, or they were resolved to the two near Pāhala.

https://www.usgs.gov/volcanoes/mauna-loa/volcano-updates

Kīlauea is erupting however, but the recent earthquakes were south of Kīlauea.

 

[Mark44]

Mauna Loa is considered the largest active volcano on Earth, rising to 13,681 feet above sea level. Mauna Loa rises up from the ocean floor of the Central Pacific at a depth of about 3 miles. Because of the volcano’s significant mass, the ocean floor directly beneath Mauna Loa is depressed by another 5 miles.

The parts in bold seem contradictory to me. If the base of the volcano is on the ocean floor at a depth of about 3 miles, how is it that the ocean floor is depressed by another 5 miles? Is the ocean floor there three miles down or eight miles down? The latter figure would put the ocean floor at a depth about equal to that of the Challenger Deep, the lowest point in the Marianas Trench, and the lowest known point in all the oceans.

According to USGS, this places Mauna Loa’s summit about 56,000 feet above its base

This is in disagreement with the Wikipedia article -- Mauna Loa - Wikipedia .

Mauna Loa rises 9,170 m (30,085 ft) from base to summit

While I would normally trust USGS over Wikipedia, the 30,000+ figure is one I've seen for years.

Regarding the warnings of impending eruptions, it's helpful to know that Mauna Loa is a shield volcano, one that erupts a very fluid basalt lava (i.e., low in silica) that can flow long distances. In contrast, volcanoes whose lava contains high concentrations of silica can explode violently, especially if the rising column of lava picks up a significant amount of water that can flash to steam when pressure on it is released. Volcanoes that ejected highly siliceous lava (rhyolite) include Mt. Mazama in Oregon (the present Crater Lake) and Mt. St. Helens in Washington state.

This is not to discount the dangers of a moving flow of red-hot lava.

 

[Astronuc]

I should have snagged them last night, but USGS recent earthquake map was showing some 2.5 to 3.2 or so earthquake in Mauna Loa. They seem to have disappeared, but I found some. Note the negative depths, which would imply above sea level.

M 2.5 - 26 km E of Honaunau-Napoopoo, Hawaii
https://earthquake.usgs.gov/earthquakes/eventpage/hv72387732/executive

• 2021-03-18 01:17:54 (UTC)
• 19.433°N 155.615°W
• -1.0 km depth

M 2.7 - 26 km E of Honaunau-Napoopoo, Hawaii
https://earthquake.usgs.gov/earthquakes/eventpage/hv72386932/executive

• 2021-03-17 13:27:48 (UTC)
• 19.467°N 155.613°W
• -1.6 km depth

M 2.5 - 27 km NNW of Pāhala, Hawaii
https://earthquake.usgs.gov/earthquakes/eventpage/hv72385342/executive

• 2021-03-16 09:39:11 (UTC)
• 19.430°N 155.595°W
• -2.5 km depth