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Hey there! 😊 Thanks so much for being here!
I'm so excited to share with you some extracts of the very first online course about Hawai'i.
The Hawaiian Island of O'ahu is a quite an urban island, however, it has some distinct landscapes worth knowing about. Have you ever wondered how Diamond Head or Hanauma Bay were formed? Learn this and more in this article about Oahu's fascinating landscapes you need to know about when planning a trip to Hawai'i.
Below you will find a video about the formation of O'ahu from the Geology Module of the world's first online course about Hawai'i: The ULTIMATE HAWAI'I TRAVEL CLASS. 😊
Read ahead if you:
- are planning a Hawai'i vacation
- already booked your vacation and are gathering information about the islands
- want to become a sustainable, responsible, informed traveler
This is lesson 5: O'ahu from module 1: Geology.
In this lesson, we will look at the geological features of O'ahu. O'ahu is located between Kaua'i and Moloka'i. Its position tells us that it has to be one of the older main Hawaiian Islands.
Formation of O'ahu
O'ahu is the remnant of 3 extinct volcanoes: Ko'olau volcano, Wai'anae volcano and Ka'ena volcano. For many years, it was believed that only the first two volcanoes built the island and by and Wai'anae was thought to be very large due to the unusual long distance to Kaua'i, the next Island. Then, the previously known submarine Ka'ena Ridge on the western tip of the island was recognized to present an even older volcano on whose flanks Ko'olau volcano and Wai'anae volcanoes erupted. It extends more than 100 km or 62 miles to the northwest and it explains the large distance from O'ahu to Kaua'i.
Wai'anae volcano started its growth around 2,8 to 3,9 million years ago. 1 million years later Ko'olau volcano started to grow. The volcanoes grew and grew larger, eventually connecting their flanks, creating the Schofield Plateau when lava flows from the Ko'olau volcano flowed towards Wai'anae volcano.
Some 1 to 1,5 million years ago a catastrophic landslide destroyed half of Ko'olau volcano due to gravitational instabilities and shaped this environment forever. This landslide is known as the Nu'uanu avalanche. Debris is can still be found 200 km or 120 miles away from the coast. However, the landslide is not believed to be the cause of the dramatic mountain and geological features we can see today: the Nu'uanu Pali, but rather due to wind and erosion.
Ko'olau and Wai'anae volcanoes have lent their names to the mountain ranges that are predominant in a O'ahu's current morphology: The Ko'olau Range on the windward, which is the eastern side, and the Wai'anae Range along the leeward or western side of the island.
O'ahu's Tuff Cones
Classical remnants of a shield volcano such as a caldera are not visible anymore on O'ahu due to advanced erosion and weathering of the volcanic rock. O'ahu, however, is decorated with many tuff cones such as Punchbowl Crater, Diamond Head, Koko Head, Koko Crater and Hanauma Bay.
In the southeast, a rift zone, called the Koko Rift Zone, extends from 3 km or 2 miles south of Koko Head all the way to Mānana Island off Makapu'u Point. It is approximately 12 km or 7,5 miles long. It formed a few 100.000 years ago when Ko'olau Mountain had a new eruption phase. Along this rift zone, we can find many geological features enjoyed today. Makapu'u Point, Koko Crater, Hanauma Bay and Koko Head.
Hanauma Bay means 'curved bay'. It is the remnant of two closely located tuff cone craters. They are 7.000 to 100.000 years old. The seaward facing crater rims were breached by waves over time and ocean water could now flow inside the craters and flood them and create this beautiful gem we can visit today. The bay is fringed by a calcareous beach and surrounded by steep crater walls. The Hanauma Bay Nature Preserve protects the living reef which covers nearly two-thirds of the crater floor. This yellowish almost white sand is composed of fragments of coral and other invertebrates derived from the erosion of marine reefs. These are also some of the most common beaches.
Koko Head and Koko Crater
Koko Head is the southernmost point of the island. This tuff cone is approximately 190 meters or 600 feet high. It is not visible in this picture. Don't confuse Koko Head with Koko Crater. Koko Crater is a large tuff cone 368 meters or 1.200 feet high and it is located northeast of Hanauma Bay. Maybe you've heard of the Koko Stairs also called Koko Crater Trail or, misleadingly, Koko Head Stairs. These stairs lead directly up to the crater peak and are quite steep, but very worth the hike. From the peak, you have a beautiful view over the coast and Hanauma Bay.
It is maybe the most characteristic feature of O'ahu Island: Diamond Head Crater or Lē'ahi. This tuff cone is located in the south of the island near Waikīkī. It is 230 meters or 760 feet high. Just as the Koko Rift Zone, Diamond Head was formed 400.000 to 500.000 years ago during an eruption of Ko'olau volcano. The eruption was explosive, destroying thousands of years old coral reefs and basalt. This is the reason why not only tuff is found in the walls of Diamond Head, but also coral fragments and basalt. The name Diamond Head was given by navigators from the 19th century who mistook the coral fragments, which are calcite crystals of whitish color, for diamonds, hence, Diamond Head.
You most certainly have heard of this beach, Waikīkī Beach in Honolulu. By the way, Honolulu is the state's capital. Waikīkī is world famous tourists come from all over the place to see this prestigious beach, but there is one thing the majority of them aren't aware of: This beach is almost completely anthropogenic, that means made by humans. Since the year 1800, when Honolulu became more and more interesting for visitors, it has been suffering from erosion problems that keep getting worse. Ever since the construction of hotels, buildings and streets nearby the coast, humans have been interfering with nature and its natural processes. Erosion has deteriorated and can't be kept in bay by natural mechanisms anymore. Sand from the beach gets washed out into the ocean and now it has to be replaced. The sand is taken from other beaches on O'ahu, from other islands such as Moloka'i and/or even pumped out of the ocean and it then is deposited in Waikīkī.
Pearl Harbor is a naturally clover-shaped bay or haven in the south of O'ahu west of Honolulu. It is known for the attack on Pearl Harbor during World War II and you will learn a little more about that in Module 4: History. The Hawaiian name 'wai momi' means 'pearl waters' and was given due to pearl oysters that used to live here. Pearl Harbor is divided into three so-called lochs: the west loch, the middle loch, and the east loch. Ford Island is located in the center. Basically, these lochs are flooded valleys, which were molded by erosion when the rock was still emerged and sea levels were lower than today, as we have seen it many times by now. It is just another example of wind and water erosion and subsequent flooding.
Lanikai Beach is a beautiful golden sand beach at the windward side of O'ahu. From here, the Mokolua Islands, in Hawaiian 'Na Mokolua', are visible. They lie 1 km or 3.200 feet off the coast. The islets belong to the Hawai'i State Sea Bird Sanctuary. They are eroded basalt dikes and are part of the Ko'olau Shield. Dikes are elongated flat, intrusions in a fractured rock body. They form when magma penetrates or cuts through pre-existing rock and crystallizes within these gaps of the fractured rock. Their position and angle is different than the rest of the structure, oftentimes cutting through the older rock vertically or diagonally.
O'ahu is an urban island, but still is able to show off some of the most fascinating landscapes in the archipelago if you know where to look - and I really hope that you now do! If you'll travel to Hawai'i, save this article and come back to read it again. And when you're in Hawai'i, remember what you learned - you'll see that these landscapes will become even more interesting - just because you know more about them. Promise! 😊
Why Becoming An EarthyUniversity Student is A Great IdeaEarthyUniversity students believe that our happiness and meaning of life as humans lies in emotional connection to nature and people. EarthyUniversity is all about feeling the insignificance of human existance, about the dominance of natural processes, about reconnecting with nature by gaining knowledge, and, last but not least, to be endlessly fascinated and inspired by this beatiful planet we live on. As a result, we'll be making better decisions for nature, ourselves and others, wherever we are in the world: at home or travelling.
If you are intrigued to learn even more about Hawai'i and want to become a sustainable, conscious traveler, I invite you to visit the website EarthyUniversity and have a look at the ULTIMATE HAWAI'I TRAVEL CLASS. I'll see you there! 😊
Be kind and love nature,
PS: Want to know more about Hawai'i's plants and how they even got to the islands? Jump to this blog post: 9 Hawaiian Plants Worth Knowing Of And How Plants Came To Hawaii
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Who wrote this article? I'm Daniela. Pleased to meet you :) Read more about me here.
[Image Credit: Koko Crater as viewed from Makapu'u Lighthouse Trail, Photograph taken by Daniela Dägele (myself :))]