The Ninole Hills, also known as the Ninole Volcanic Series, are steep eroded hills of

shield A shield is a piece of personal armour held in the hand, which may or may not be strapped to the wrist or forearm. Shields are used to intercept specific attacks, whether from close-ranged weaponry like spears or long ranged projectiles suc ...

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

s on the south side of the

Island of Hawaii Hawaii is the List of islands of the United States by area, largest island in the United States, located in the Hawaii, state of Hawaii, the southernmost state in the union. It is the southeasternmost of the Hawaiian Islands, a chain of volcani ...

. Recent data suggests that these hills are either the remnants of large

escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Due to the similarity, the term '' scarp'' may mistakenly be incorrectly used inte ...

s that pre-date the

Mauna Loa Mauna Loa (, ; ) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. Mauna Loa is Earth's largest active volcano by both mass and volume. It was historically considered to be the largest ...

volcano (the largest active volcano in the world), or uplifted blocks from the oldest parts of the Mauna Loa fault system. The Ninole Hills are remains of the top rim of a big deep hollow left when the prehistoric Punaluu landslide slid away. The rim over time eroded into deep canyons as lava from

ran down into the hollow and slowly filled it instead of burying the rim area, until now parts of the tops of the inter-canyon ridges are still unburied. It is apparent from the ruggedness of the eroded hills that they are much older than the surrounding landscape. Most of the surface of Mauna Loa is thought to have formed within the last 4,000 years, but the Ninole Hills are estimated to be between 100,000 and 200,000 years old. During this period there seem to have been massive failures in the support of the south wall of Mauna Loa, resulting in

debris Debris (, ) is rubble, wreckage, ruins, litter and discarded waste, garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can ref ...

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

s that removed chunks out of the volcano, revealing remnants of the older sections of Mauna Loa.

Footnotes

Landforms of Hawaii (island) Hills of the United States {{Hawaii-geo-stub