kids encyclopedia robot

Gardner Pinnacles facts for kids

Kids Encyclopedia Facts
The guano-coated Gardner Pinnacles.
Hawaiianislandchain USGS
Map showing the location of Gardner Pinnacles in the Hawaiian island chain
Gardner map lrg
Map of Gardner Pinnacles

The Gardner Pinnacles (Hawaiian: Pūhāhonu) are two barren rock outcrops surrounded by a reef and located in the Northwestern Hawaiian Islands at 24°59′56″N 167°59′58″W / 24.99889°N 167.99944°W / 24.99889; -167.99944.

The volcano is 511 nautical miles (946 km; 588 mi) northwest of Honolulu and 108 miles (94 nmi; 174 km) from French Frigate Shoals. The total area of the two small islets—remnants of an ancient volcano that is the world's largest shield volcano—is 5.939 acres (24,030 m2). The highest peak is 170 feet (52 meters). The surrounding reef has an area in excess of 1,904 square kilometres (470,000 acres; 735 sq mi).

The Gardner Pinnacles were discovered and named in 1820 by the whaling ship Maro. The island may be the last remnant of one the largest volcanoes on Earth.


Log of the Kaalokai. (1909) (14592257528)
A drawing of Gardner Pinnacles in 1909

The Gardner Pinnacles were first discovered on June 2, 1820, by the American whaler Maro, commanded by Captain Joseph Allen.

In 1859, the position of Gardner Pinnacles was determined by the survey schooner USS Fenimore Cooper.

The Gardner Pinnacles are home to the Giant Opihi (Cellana talcosa), Hawaiian Limpet known as the ‘opihi ko‘ele, which is not found anywhere else in the world outside the Hawaiian Islands. Numerous insects live on the island.

In 1903 Gardner Pinnacles became a part of the Hawaiian Islands Bird Reservation. In 1940 it became a part of the Hawaiian Island's National Wildlife Refuge.In the 21 century it is part of Papahānaumokuākea Marine National Monument wildlife refuge

Gardner Pinnacles was used for an emergency helicopter landing spot for the Hawaiian HIRAN project, an effort to determine location of area islands with great precision for navigational purposes. In the Hawaiian Archipelago, adjacent islands/reefs are French Frigate Shoals to the southeast, and Maro Reef to the northwest.


Starr 990524-0854 Portulaca lutea
Gardner Pinnacles
Starr 990524-0853 Portulaca lutea

The island is made up of basalt rock, which comes from lava. The rock is dark grey and dense.

According to a 2020 report in Earth and Planetary Science Letters, Pūhāhonu contains approximately 150,000 cubic kilometers of rock, based on a 2014 sonar survey. This would make it Earth's largest single volcano. Only about one-third of that volume is exposed above the sea floor. The rest is buried beneath a ring of debris, broken coral, and other material that has eroded from the peak. By comparison, from sea floor to peak, Mauna Loa, on Hawaii’s Big Island, is the tallest shield volcano on Earth. But it is nowhere near as massive as Pūhāhonu; a 2013 study estimates Mauna Loa’s volume at 83,000 cubic kilometers. Pūhāhonu is so heavy, researchers note, that it has caused Earth’s crust nearby—and thus the volcano itself—to sink hundreds of meters over millions of years.

The Puhahonu volcano (Gardner) would be twice as big as Mauna Loa's based on that research.

The Tamu Massif, a 4-kilometer-tall volcanic feature the size of the British Isles on the sea floor east of Japan, contains almost 7 million cubic kilometers of material and was once thought to be the world’s largest shield volcano. But Tamu Massif is now believed to have formed along a midocean ridge rather than over a single source of magma. That makes Pūhāhonu the largest known shield volcano on Earth.


The island has one plant known to grow on it, the succulent sea purslane. However, there are over a dozen species of bird observed here, many nesting. There is also a variety of insect species on the island.

In the surrounding waters there is variety of sealife, which is noted as habitat for a limpet, the giant ophi which lives in tidal areas of the rocky island. There are many species of fish and coral life in the nearby waters.

The large numbers of birds have coated many surfaces of the island in guano, giving it a whitish appearance.

Some of the fish species in the nearby waters include red lip parrotfish, doublebar goatfish, and reef triggerfish.


The name Gardner comes from its discovery in 1820, when the Captain Joseph Allen of the ship Maro named it Gardner's Island. They also discovered Maro Reef, which is named for that sailing ship.

It has sometimes been called Gardner Rock or Gardner Island, Besides Gardner Pinnacles.

The Hawaiian name, Pūhāhonu, means 'turtle surfacing for air', from pūhā 'to breathe at the surface' and honu 'turtle'.

kids search engine
Gardner Pinnacles Facts for Kids. Kiddle Encyclopedia.