When the alarms were tripped at the Hawaiian Volcano Observatory one day earlier this month, scientists thought the low-frequency sound being picked up by field sensors was coming from one of Hawaii’s volcanoes.

“We were trying to figure out what the signal was. Was it Mauna Loa or what?” recalled David Phillips, deputy scientist-­in-charge at the Big Island U.S. Geological Service outpost.

After a few minutes the scientists came to the realization that the sound was actually emanating from Tonga, where the mighty eruption of an undersea volcano Jan. 14 sent an atmospheric shock wave reverberating across the Pacific.

Earth’s most powerful volcanic blast in 30 years triggered a tsunami that swamped the island nation’s coastal regions and created a giant mushroom cloud that covered the archipelago with a thick coat of ash.

The scary episode, captured by satellite images, left more than a few people in Hawaii wondering whether the same thing could happen here. After all, Hawaii has its own active submarine volcano, commonly called Loihi, 22 miles southeast of Hawaii island.

Experts say that while you can never say never, it’s highly unlikely the same thing could happen here — at least not for tens of thousands of years.

One of the main reasons, they say, is that the summit of Loihi — last year renamed Kamaehuakanaloa, or Kamaehu for short — sits too deep in the ocean, much more so than the Tonga volcano. Another reason is that the chemical makeup and composition of the basaltic magma that feeds the volcanoes in Hawaii make it much less likely here to generate such a massive explosion.

Volcanologist Ken Rubin, University of Hawaii at Manoa earth sciences professor, said the type of magma that supplies Hawaii’s volcanoes is more fluid than the kind that feeds Tonga’s. The runny magma allows gas bubbles to more easily escape, whereas in Tonga the magma is more viscous and more likely to trap the gas.

“This stuff (in Tonga) inherently has more gas in it and is stickier, so bubbles form but have more difficulty escaping from it, and when they do escape they rip the magma apart and it tends to erupt more explosively,” he said.

The kind of magma that supplies Tonga’s volcanoes is called andesite, which is also common in the Andes and in places like Japan, Alaska and the Cascades, where explosive eruptions, pyroclastic flows and huge columns of ash are more common.

The Hunga Tonga-Hunga Haapai volcano is also fairly close to the ocean surface — only a few hundred feet — and the water on top of it was heated very quickly and flashed to steam, a phenomenon that helped drive the explosion, Rubin said.

The summit of Kamaehu, by comparison, is more than 3,000 feet below the surface of the ocean, and the weight of the water tends to suppress any explosive tendencies, he said.

Phillips said that with Kamaehu so far beneath the waves, the USGS considers the volcano a low to very low threat and will continue to monitor it from afar. He said there are no immediate plans to place monitoring instruments on the seamount.

That’s not to say there aren’t any dangers from the undersea volcano. One is the chance of a landslide-­triggered tsunami.

“It’s very difficult to know how likely an event like that is or when it might happen, but there is evidence on the sides of the volcano for large landslides in the past,” Rubin said.

The volcano has some seriously steep slopes — similar to the Koolau range as viewed from the Windward side — and it’s very possible that there could be a landslide big enough to displace enough water to generate a sizable tsunami, the professor said.

Rubin said no one has ever uncovered direct evidence from the Big Island’s south coast, for example, that a tsunami from Kama­ehu ever happened.

“The tsunami is therefore more of a hypothesis, but the landslides are not,” he said.

From the bottom of the ocean to its summit, Kama­ehu stands about 10,000 feet tall — about the size of Haleakala from sea level to its summit.

No one knows how old Kamaehu is, but some have speculated it is 100,000 to 150,000 years old, an estimate based on comparisons with other submarine volcanoes. According to HVO, Hawaii’s volcanoes are thought to breach the sea surface about 300,000 years or so after their birth, so Kamaehu might be only halfway to becoming an island. If true, that would mean it wouldn’t happen for another 150,000 years.

While Hawaii eruptions are typically less explosive, that doesn’t mean there aren’t some potential fireworks in Kamaehu’s future. Rubin noted that Diamond Head and Koko Head, with their large craters compared with rim size, were formed in an explosive style.

“But we don’t expect that to occur (at Kamaehu) for thousands if not tens of thousands of years,” he said.

Kamaehu’s last known eruption was in 1996, when HVO detected 4,377 earthquakes at the seamount over about four weeks in the summer.

But the youngest volcano in the long line of the Hawaiian-Emperor chain will indeed erupt again, scientists say. It will one day become an island and eventually become part of the Big Island as it grows and as Mauna Loa and Kilauea continue to expand.

The volcano’s former name, Loihi, means “long” in Hawaiian. The name was created in 1955 simply to describe the elongated shape of the seamount.

Recently, Hawaiian scholars, including Ku‘ulei Kanahele of the Edith Kanaka‘ole Foundation, have brought to light ancient mele that describe Kamaehu, the reddish child of Haumea (earth) and Kanaloa (sea) that rises from the ocean floor like a submarine volcano.

The formal name Kama­ehuakanaloa was unanimously adopted in July by the Hawaii Board on Geographic Names.