Hawaii Center for Volcanology | Hawaiian Volcano General Information

The main Hawaiian Islands are the tops of giant undersea shield volcanoes that formed at the Hawaiian hotspot, which is presently under the southeast portion of the Big Island of Hawaii. Shield volcanoes are gently sloping mountains produced from a large number of generally very fluid lava flows.

    How many Hawaiian Island are there? There are 8 main islands, which make up the state of Hawaii (Hawaii, Maui, Oahu, Kahoolawe, Lanai, Molokai, Kauai and Niihau). There is one additional small island (Kaala) near Niihau that is often overlooked. The outer Hawaiian Islands (also known as the Northwest Hawaiian Islands, and since 2006 part of the Papahanaumokuakea Marine National Monument) are a series of 9 small, islands and several shallow banks that sit northwest of Kauai, extending from Nihoa to Kure. The older Hawaiian islands are the above-sea-level remnants of once much larger volcanic mountains, which have cooled, eroded and subsided as they have moved northwest with the Pacific Plate to their current location.

    Together outer islands and the main islands make a total of 18 commonly accepted islands. Depending on how you count them, there are also more than a hundred additional small rocks and islets among the Hawaiian Islands that are either volcanic, marine sedimentary or erosional in origin, which when combined with the other 18, total to perhaps as many as 130 or so in the entire Archipellago.

   If you would like to learn more about how the Hawaiian islands formed from a single mantle hotspot, visit our Formation of the Hawaiian Islands web page. All three active Hawaiian volcanoes (Mauna Loa, Kilauea and Loihi) share the Hawaiian hot spot, but retain unique volcanic histories and compositions. You can view a schematic representation of the geometry of this situation HERE

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Hawaiian Lava Flow Types

Pahoehoe and 'a'a are two words in the Hawaiian language that are commonly used by modern scientists (especially geologists and volcanologists), as well as volcano-interested lay persons from around the world, to describe some lava flows. Pahoehoe is a smooth or ropey surfaced lava flow and 'a'a is a clinkery, rough, broken surfaced lava flow.

    But what did these words mean to Hawaiians of times past, and where did these names come from?

Many geology texts define "pahoehoe" and "aa" in the above manner, the latter commonly thought to mimic the sound of a person painfully crossing an 'a'a lava flow in bare feet.

    Neither of these definitions jive with the formal definitions of these words in pre-western Hawaiian. According to the Hawaiian Dictionary by Pukui and Elbert (a definitive text), Pahoehoe literally means smooth and unbroken, or satin (i.e., the fabric). The surface texture we volcanologists associate with Pahoehoe as a defining physical feature is not actually part of the etymology of the word (Hawaiians have numerous words for "rope" and "cord" and none is similar to pahoehoe). The word 'a'a has numerous meanings (for instance, a small root or vein, stony, to brave or challenge, to burn). Perhaps it is the stony and burning definitions of the word that caused the Hawaiians to name certain types of lava flows 'a'a. True, 'a'a flows are full of sharp, loose rubble on their surfaces, and are not fun to walk accross, but it is probably a modern "myth" that this name evolved to evoke the pain of walking on an 'a'a flow.