Introduction to the Big Island of Hawaii
Are you interested in the incredible geologic story of the Big Island of Hawaii? It’s worth learning about if you’re planning a trip to the islands! From its origin as a single shield volcano to its current landscape of five major volcanoes, each with its own unique shape and characteristics, the Big Island has a fascinating geologic history. Explore this incredible story with us!
The Big Island of Hawaii is the largest and youngest island of the Hawaiian Islands. Spanning 4,028 square miles of stunning geologic landscape, it is nearly twice as big as all of the other islands combined. It is located in the southeasternmost part of the archipelago and is home to five subaerial volcanoes, two of which are still active today.
The Big Island formed around 700,000 years ago as the Pacific Ocean floor moved over a hot spot, and its geology has been shaped by the tectonic plates and molten rock that form the islands. The average grain size (Phi-median) of Hawaii beach sand differs by island, with Oahu having more coastal plain and reefs, as well as the greatest urban development.
The Big Picture: Geology of the Island
The Big Island of Hawaii is located thousands of kilometers away from the nearest plate boundary, yet it is still volcanically active. This is due to the oceanic crust on which the Hawaiian Islands reside being nearly 90 million years old, yet the oldest of these islands was formed a mere 5 million years ago. This fascinating geologic history can be explored mile by mile along the island’s major roads with the help of several dozen maps and diagrams included in a book that explains it all. One example of this is the high cliffs of Kealakekua Bay (west side Hawai’i Island) which were formed as a result of a large Mauna Loa landslide (‘Ālika 2), offering a stunning view to east-southeast.
A Chain of Islands: Hawaiian Hot Spot
The Big Island of Hawaii is part of a chain of islands that were formed by a hotspot in the Earth’s mantle. This hotspot is an area where magma from deep within the Earth rises and erupts onto the surface. As the Pacific Plate moves, it carries the islands away from the hotspot, forming a chain of islands or seamounts on the seafloor. The Hawaiian Islands are made up of 132 islands and atolls that stretch nearly 2,400 miles. The Big Island itself is comprised of five subaerial volcanoes and one submarine volcano, each with its own geologic history and age.
Five Subaerial Volcanoes of the Big Island
The Big Island of Hawaii is made up of five subaerial shield volcanoes, namely Mahukona, Kohala, Maunakea, Hualalai, Mauna Loa, Kilauea and Kamaʻehuakanaloa. These volcanoes have been formed over thousands of years by the Hawaiian hot spot and are all in various stages of growth. The youngest volcano is Kilauea which has been erupting constantly since 1983, while the oldest is Kohala which is estimated to have last erupted around 60,000 years ago.
Mauna Loa and Mauna Kea are two of the most active volcanoes on the island, although they are both currently in a dormant stage. These five subaerial volcanoes have provided the Big Island with its unique geologic history and have shaped its landscape over time.
Mauna Loa and Kilauea Volcanoes – Active Volcanoes
The Big Island of Hawaii is home to seven volcanoes, with four of them being active. The two most active volcanoes are Mauna Loa and Kilauea. Mauna Loa is the world’s largest active volcano and is known for its large shield shape and several eruptions over the years. Kilauea is the world’s most active volcanic mass and has been erupting continuously for more than a year since 2018. The hotspot behind these volcanoes is thought to be located beneath the Hawaiian archipelago’s youngest and most active landmass, the Big Island of Hawaii, where molten rock forms the islands. Between 1912 and 2012, there were nearly 50 Kīlauea eruptions, 12 Mauna Loa eruptions, and one eruption of both Mahukona and Hualalai.
The Age of the Hawaiian Islands
The Hawaiian Islands have an interesting and long geologic history. The oldest of the islands, Kauai, is estimated to be around five million years old, while the youngest, the Big Island, is only 400,000 years old. Scientists studying the age of the islands were able to calculate their age by using radiocarbon dating on lava rocks found in the islands.
It was discovered that the age progression from island to island is systematically younger towards the southeast. This bend in the chain separates the older Emperor Seamount Chain from the younger Hawaiian-Emperor Seamount Chain. The formation of each island was caused by volcanic activity and tectonic plate movement which allowed molten rock to form up from the oceanic crust beneath.
Tectonic Plates and Molten Rock Forming the Islands
The Hawaiian Islands were formed by a volcanic hot spot, the Pacific Plate sliding over a plume of magma—molten rock—puncturing Earth’s crust. As tectonic plates moved ever eastward across this fissure, molten rock created islands. But as the top of the mountains reached shallower water depths, islands began to emerge above sea level and form the Hawaiian archipelago.
Tectonic plates and magma interacted to form five subaerial volcanoes of the Big Island, as well as the other islands in the chain. The hotspot, which geologists estimate began producing the Hawaiian Islands 30 million years ago, is a plume of molten rock that rises through the mantle and continues underwater as a series of seamounts. The movement of the tectonic plates and associated volcanic activity are responsible for creating the Hawaiian islands, including the Big Island.
Formation of the Big Island and its Six Volcanoes
The Big Island of Hawaii is the largest of the 137 islands in the archipelago. It was formed by a volcanic hot spot, an upwelling plume of magma, which created new islands as the Pacific Plate moved over it. The Hawaii Emperor seamount chain is a well-known example of a large seamount and island chain created by this hot spot. Six volcanoes coalesced, or joined, to form the Big Island: Mahukona Volcano, Kohala Volcano, Maunakea Volcano, Hualalai Volcano, Mauna Loa Volcano, and Kilauea Volcano. All six volcanoes are located along the southeastern shore of the Big Island of Hawaii.
The Island of Hawaii is between 210,000 and 280,000 years old and emerged above sea level about 40 to 70 million years ago. The steep slopes on Mauna Kea owe their formation to an explosive type of eruption in the recent geologic past. Explosive eruptions often produce widespread ash and lava flows that shape the land surface. Today, Hawaii has active volcanism, with both Mauna Loa and Kilauea Volcanoes erupting every now and then.
The Impact of Plate Movement and Shallower Waters
The movement of tectonic plates is an important factor in the formation of the Hawaiian Islands. Plate motion is responsible for the formation of the volcanic hot spot that created the islands, and it is also responsible for the expansion and contraction of the islands over time.
Plate motion has also had an impact on the formation of shallower waters surrounding the islands, as well as providing a source of molten rock that forms the islands. Plate motion has played a major role in the geologic history of the Big Island of Hawaii, and its effects can still be seen today.
Conclusion
In conclusion, the geologic history of the Big Island of Hawaii is one that is complex and fascinating. From plate tectonics to the creation of volcanoes, the Big Island has gone through many changes over time. It is home to five subaerial volcanoes, two of which are still active today.
The Hawaiian hot spot has created a chain of islands, with the Big Island being the youngest and most active. Plate movement and shallower waters have shaped the Big Island and its six volcanoes, and continue to do so today. This is a unique geological formation that makes Hawaii one of the most interesting places on Earth.
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