Mauna Loa volcano at Hawai'i Volcanos National Park has been releasing a heightened number of earthquakes daily/NPS file, Janice Wei

A jump in the daily number of earthquakes that are shuddering beneath Mauna Loa at Hawai'i Volcanoes National Park has prompted a backcountry closure at the volcano's summit.

The U.S. Geological Survey's Hawaiian Volcano Observatory noticed an uptick in earthquakes beneath the iconic volcano in July and August, when the daily number of temblors doubled from 5-10 a day to 10-20. More recently, 40-50 quakes a day have been recorded over the past two weeks, the observatory reported. On September 23rd and 29th, there were more than 100 earthquakes a day, it added.

However, Mauna Loa has not shown any signs that an eruption is imminent, the observatory said in a release.

"Inflation or expansion of Mauna Loa's summit is accompanying the earthquake activity and has also increased in the past two weeks," said the release. "The last time Mauna Loa displayed similar elevated earthquake activity and expansion of the summit region was late-January to late-March of 2021. Additional periods of increased earthquake activity have also occurred during the 38 years since the last eruption of Mauna Loa in 1984."

At the national park, officials on Wednesday closed the Mauna Loa summit backcountry due to the increased seismic activity. However, they said in a release, the Mauna Loa Road and the Mauna Loa Lookout at 6,662 feet elevation remain open to the public.

While the Hawaiian Volcano Observatory has been providing weekly updates of Mauna Loa's geologic activity, for the immediate future it will be providing daiy updates.

Rising to more than 2.5 miles (4 kilometers) above sea level, Mauna Loa, a shield volcano, is the largest active volcano on Earth. According to the USGS, the Hawaiian name "Mauna Loa" means "Long Mountain." It is among Earth's most active volcanoes, having erupted 33 times since its first well-documented historical eruption in 1843, the agency adds. "It has produced large, voluminous flows of basalt that have reached the ocean eight times since 1868. It last erupted in 1984, when a lava flow came within 4.5 miles (7.2 kilometers) of Hilo, the largest population center on the island."

Kīlauea, Mauna Loa's sister volcano in Hawai'i Volcanoes National Park, erupted for months in 2018, with the national park suffering significant damage, as did surrounding communities. Those eruptions covered nearly 13 square miles of the island with lava flows, which also forced thousands to evacuate their homes; more than 700 homes were destroyed by the eruptions. Damage estimates ran to at least $100 million, with the park's Crater Rim Drive significantly cracked and buckled while the park's Jagger Museum sustained significant structural damage from thousands of related earthquakes.

A summit eruption that began within Kīlauea's Halema‘uma‘u crater on September 29, 2021, is ongoing, the USGS notes.