Sip back and discover Hawaii the 50th U.S. State known as the Aloha State as we explore the geodiversity and fossils of the oldest, most remote and longest archipelago of 137 oceanic islands, atolls, volcanos, guyots or seamounts in the world dating back the Cretaceous Period – many of which are submerged. The Hawaiian Island archipelago is the southerly part of a 6,500Km Hawaiian–Emperor Chain of volcanic formations that starts with the oldest submerged atolls in the Northern Pacific Ocean known as the Emperor Seamount in the Aleutian Trench of Alaska and stretches south east to the eight main Hawaiian Islands or high islands of Hawai‘i, Maui, Koho‘olawe, Moloka‘i, Lana‘i, O‘ahu, Kaua‘i and Ni‘ihau. Volcanic activity is still occurring today and a new island called Kama‘ehuakanaloa formerly known Lō’ihi is slowly emerging below the sea off the southern shore of the Big Island or the Island of Hawaiʻi the youngest and largest island in the Hawaiian chain. Hawaiʻi is also home to the Hawai'i Volcanoes National Park where visitors can witness the power of Kīlauea and Mauna Loa among Earth's most active volcanoes.
Visiting Hawaii
The capital of the State of Hawaii is Honolulu on the island of Oahu’s south shore a 6-hour direct flight from San Francisco or nearly a 9-hour flight from Auckland in New Zealand. The Hawaiian Islands offer a unique blend of natural beauty, rich culture, and outdoor adventure, making them a dream destination for travellers to explore. Each island has its own character, from the bustling beaches of Oʻahu to the volcanic landscapes of the Big Island, the lush valleys of Kauaʻi, and the serene shores of Molokaʻi and Lānaʻi.
Among the must-see destinations is Waikīkī Beach a world-famous surf and resort area. Visitors can also explore Pearl Harbour National Memorial, hike the enigmatic Diamond Head crator or experience Polynesian culture at the Polynesian Cultural Centre. Maui is known for its stunning beaches and the scenic Road to Haleakalā National Park where visitors can watch the sunrise above the clouds.
The Big Island or Hawaiʻi Island offers diverse landscapes from black sand beaches to active lava flows in Hawaiʻi Volcanoes National Park. Kauaʻi known as the "Garden Isle," is famous for its lush rainforests, dramatic cliffs of the Nā Pali Coast State Wilderness Park and the breath-taking Waimea Canyon State Park known as the "Grand Canyon of the Pacific". Visiting Hawaii offers an unforgettable experience filled with natural wonders and cultural heritage.
The Geodiversity of Hawaii
The Hawaiian Island archipelago is a continuous trail of hot spot volcanic eruptions formed by a plume of magma known as a hotspot that has punctured the main body of the slow moving Pacific Tectonic Plate rather than typically breaching the tectonic plate boundary to release molten magma and produce vast basaltic lava flows.
Though much of the Hawaiian Islands are principally made up of igneous rock there are also fossils to be found that tell a story of the last 400,000 years of the Islands biodiversity.
During the Late Cretaceous around seventy million years ago the Hawaiian hotspot erupted through the main body of the Pacific Tectonic Plate. Still today this thermal plume of less dense molten rock or mantle continues to circulate to the Earths surface and repeatedly erupts through the seafloor forming the Hawaiian–Emperor Volcanic Chain (H-E Chain) including the eight main Hawaiian Islands made up of 15 volcanoes and are the youngest in a chain of more than 129 volcanoes located above and below sea level.
The backdrop to the Hawaiian–Emperor Volcanic Chain is the fact that the Pacific Tectonic Plate is continuously moving north westwards at a rate of roughly 8cm per year whilst the Hawaiian hotspot remains stationary.
Though, its interesting to note that between approximately 47 - 55 million years ago there was a change in direction called the H-E Bend and is still debated today as to whether this was the result of the hot spot drifting or a Pacific Tectonic Plate change in direction. The Hawaiian hotspot currently sits beneath island of Hawaiʻi erupting new lava at Kīlauea volcano and at Kama‘ehuakanaloa formerly Lō’ihi the youngest submerged active volcano in the chain about 35Km off the southeast coast of the island of Hawaii.
The evolution of the volcanic formations of the Hawaiian–Emperor Volcanic Chain starts with a magma eruption on the seafloor above the hotspot. Over time basalt accumulates creating a submarine shield and the deep oceanic water pressure traps the gases of oxygen, carbon dioxide and hydrogen sulphide dissolved in the magma.
As the volcanic shield breaches the ocean surface the magma chemistry changes and the once trapped gases become decompressed under the lower pressure and exsolve to form the characteristic bubbles or holes in the lava known as vesicles.
An active volcano above the hotspot continues to grow for about 2 million years into a classic shield-shaped volcano and further eruptions are fuelled by shallow magma reservoirs located beneath their summits. Eventually as the hotspot moves on the volcanos summit collapses forming of a caldera or a steep-walled crater that crowns many shield volcanoes.
As the hotspot moves away the caldera becomes capped and the frequency of eruptions slows until it becomes dormant and begins to become shaped by the forces of a tropical climate where weathering and erosion to produce soils, waterways and the availability of nutrients the building blocks for an emerging ecosystem.
The same is true for the adjacent shoreline. As the volcanoes become dormant incipient or early stage reefs begin to form. Overtime these reefs extensively grow to eventually encircle the volcanic island as a well-developed fringe reef that attracts marine life. Volcanoes as young as Mauna Loa are host to incipient reefs while the older islands of O’ahu and Kaua’i have extensive well-developed fringing reefs.
As the Hawaiian volcanoes transition from being dormant to extinct and are now much further way from the hotspot the lithosphere around them has now cooled and becomes increasingly dense leading to the subsidence of the caldera into the ocean.
Over time the volcanic island erodes away until only the circular reef remains forming an atoll. Today, nearly all of the north western Hawaiian Islands are atolls. Further continuation of this subsidence inevitably fully submerges or drowns the established fringe reef below the sea level to form a flat-topped seamount or guyots that make up the northerly Emperor Seamounts.
The Fossils of the Hawaiian Islands
A traditional fossil record is often captured in sedimentary rock that is millions of years old but given the Hawaiian Islands relatively recent volcanic origins and igneous rock the fossil record is found in sand dunes, lava tubes, caves, reefs and charcoalised imprints in lava flows.
The fossil record of Hawaii includes plants, birds, fish, mammal, terrestrial and marine invertebrates tell a story of the islands remoteness where early colonisers either flew, floated or were transported across the Pacific Ocean.
Given that the Hawaiian Islands are predominantly igneous rock its not surprising that the volcanic lava has played a role in preserving the fossil record. As lava flows from a volcanic vent the out surface can cool much quicker than the inner molten sections. As the outer layer of lava solidifies it insulates the hotter flowing lava within allowing it to travel further.
Over time the remaining molten lava drains out leaving behind a hollow tunnels or lava tubes. These can vary in size from being very small to becoming vast underground networks. These lava tubes can collapse over time creating skylights that allow access to animals and plants.
Among the fossil record of the Makaopuhi Lava Tube and Kīlauea Lava Tubes of the Hawaiʻi Volcanoes National Park and the Waiū o Hina lava tubes on Mauna Loa has been Hawaiian rails, ducks, land snails and also Hawaii’s only native land-based mammal the ʻŌpeʻapeʻa (Hawaiian for "Half Leaf") or Hawaiian Hoary Bat (Lasiurus semotus). This small and solitary bat is believed to have arrived in the Hawaiian Islands thousands of years ago blown in by strong storms.
The other feature of fossil preservation by lava is the formation of tree molds. Lava tree molds forms when a flow of molten lava engulfs a tree and creates a cylindrical hollow once the tree burns away or decays. This process typically occurs in slow-moving pāhoehoe lava flows formed from non-violent eruptions that allow enough time for the lava to surround the tree without immediately incinerating it.
These formations are common in volcanic regions where lava flows have moved through forests. Notable examples can be seen in Lava Tree State Monument on the Big Island where numerous molds stand as evidence of past lava flows.
Among the richest fossil records of the Hawaiian Islands is its record of now extinct birds that date from the start of the Quaternary Period some 2.6 million years ago to the current Holocene Epoch. Many of the bird’s species numbering over 33 became extinct primarily due to predation and habitat loss by early settlers.
The largest collection of fossil bird remains have been found in the cliffs and sand dunes on the islands of Molokai, Oahu and Kauai and lava tubes of Maui and Hawaii. Among the birds were fours species of Moa-nalo or “lost fowl” a very large and flightless duck found on Kauai, Oahu, Molokai, Maui, Lanai along with geese, sea eagle, Hawk, Ibis, crows, owls and many different types of Hawaiian Finch called Hawaiian Honeycreepers.
The coral reefs and uplifted limestone on the Hawaiian Islands of Maui, Lanai, Molokai, Oahu and Kaua’i date from the Pleistocene Epoch around 2.6 million years ago to the current Holocene Epoch are rich in preserved bivalves and gastropods including Turbo sandwicensis a species of sea snail.
At this point its important to mention and recognise that Hawaii is also home to some of the most significant rock carvings or petroglyph sites in the Pacific Region and they offer a snapshot into the lives and traditions of ancient Hawaiians.
These petroglyphs or ki‘i pōhaku were created by chiselling lava rock to depict human figures, animals, canoes, and intricate geometric designs. They are believed to have been made by early Polynesian settlers centuries ago, with some dating back over a thousand years.
One of the most famous sites is the Puʻuloa Petroglyphs in Hawaiʻi Volcanoes National Park. This site contains thousands of carvings, many of which depict human-like figures and dots and thought to represents rituals. Another important site is Puakō Petroglyph Archaeological Preserve on the Kohala Coast, which features over 3,000 carvings, including warriors, turtles, and celestial symbols dating back 1200AD.
The meanings of these petroglyphs remain a mystery, but they likely served religious, navigational, or historical purposes. Some may have marked important events, such as births or battles, while others could be connected to Hawaiian spiritual beliefs. Today these petroglyph fields are protected and visitors are encouraged to observe them with respect as they provide invaluable insight into the cultural heritage of Hawaii’s first inhabitants.