How Old Is The Big Island Of Hawaii?

The Hawaiian Islands are renowned across the world for their volcanic origins, lush landscapes, and idyllic beaches. Their creation itself is a remarkable story of how the Earth’s internal fires can build new lands over millions of years.

If you’re short on time, here’s a quick answer to your question: The Big Island of Hawaii is approximately 0.43 million years old.

In this comprehensive guide, we will explore the complete geological history behind the formation of Hawaii’s largest island to understand how old the Big Island really is. We’ll learn about hotspot volcanism, shield volcanoes, lava flows, and dating techniques to trace the Big Island’s origins back nearly half a million years.

Understanding Hotspot Volcanism and the Hawaiian Hotspot

What Is a Hotspot?

A hotspot is a portion of the Earth’s mantle that contains abnormally hot rock that rises towards the surface. As the hot material rises and penetrates the crust, it can lead to volcanic activity at the surface. Famous examples of hotspots include the Hawaiian hotspot and the Yellowstone hotspot.

There are over 50 known hotspots around the world, but the origins of hotspots are still debated by geologists. Some possible explanations are:

• Plumes rising from the core-mantle boundary
• Small-scale convection cells in the mantle
• Cracks in tectonic plates above heat sources

Regardless of their origins, we know that hotspots produce chains of volcanoes over millions of years as tectonic plates drift over them. The Hawaiian Islands formed in this way over the Hawaiian hotspot in the middle of the Pacific Ocean.

The Hawaiian Hotspot

The Hawaiian hotspot is located near the southeastern edge of the Pacific plate. It is responsible for creating the Hawaiian island chain, with the youngest island, Hawaiʻi, currently centered over the hotspot.

As the Pacific plate moves to the northwest by approximately 3 inches per year, volcanoes form over the hotspot before becoming inactive and eroding. This process has built the island chain over at least 80 million years.

Studies of lava composition reveal that the Hawaiian plume may originate from around 1,800 miles deep near the core-mantle boundary. It produces huge volumes of basaltic lava, creating the massive shield volcanoes characteristic of hotspot islands.

Scientists are still researching important questions about Hawaiian volcanism, like what controls eruptive frequency and how much magma supply varies over time. Monitoring current hotspot activity also helps scientists issue warnings about volcanic hazards to Hawaiian residents and tourists.

The Origins of the Hawaiian Island Chain

The Movement of the Pacific Plate

The Hawaiian Islands were born from volcanic eruptions caused by a hot spot under the moving Pacific tectonic plate. Over millions of years, magma has pierced through the plate at this relatively fixed hot spot, creating volcanoes that eventually became high islands as the Pacific plate drifted northwest at about 32 miles per million years (USGS).

Imagine a conveyor belt moving across a focused flame. As the flame touches the belt, it burns holes through it. Similarly, as the Pacific plate glides over the hot spot, volcanoes develop, grow, drift off the hot spot, stop erupting and erode over time, creating the Hawaiian Island chain.

Evolution of the Main Hawaiian Islands

The newest island in the chain is the Island of Hawaiʻi, also known as the Big Island. At less than 1 million years old, it is still centered over the hot spot. The older islands northwest of Hawaiʻi, like Maui and Oʻahu, have moved off the hot spot and have stopped erupting, though they show evidence of past volcanic activity.

Kauai, the oldest of the main islands at over 5 million years old, has substantially eroded after drifting off the hot spot. Over millions more years, the Big Island’s volcanoes will also eventually cease erupting, and it too will erode down to become a flat, barely visible island under the sea, like the other northwestern Hawaiian Islands past Kauai.

Clearly, the Hawaiian archipelago has origins tied to Earth’s inner workings. As author Mark Twain fittingly described the islands – “The islands are not a product of chance or whimsy. They are integral parts of mainland America welded to it by the cataclysmic fires of creation.”

The Geology of the Big Island of Hawaii

Mauna Loa Volcano

The Mauna Loa volcano makes up over half of the Big Island’s land area, making it the largest active volcano on Earth. This massive shield volcano has erupted over 30 times since written records began in 1832, with flows covering over 102 square miles of land.

Its most recent eruption was in 1984, lasting 22 days and producing lava within 6 miles of the city of Hilo. Standing at 13,679 feet above sea level, Mauna Loa erupts basaltic lava in fluid flows thanks to its low silica content.

This allows the lava to travel far – in one 1950 eruption, flows reached the ocean over 21 miles away in under 3 hours.

Scientists closely monitor Mauna Loa with seismometers and GPS to predict future activity. Increased seismic activity and ground swelling typically precede an eruption. Predicting eruptions allows residents in lava flow zones time to prepare and evacuate.

The Hawaiian Volcano Observatory issues warnings and provides educational resources to keep the public informed.

Kilauea Volcano

The Kilauea volcano is one of the world’s most active volcanoes, with 34 eruptions since 1952. Located on the southeastern flank of Mauna Loa, Kilauea erupts much more fluid basaltic lava, causing slow-moving flows that allow scientists to study eruption dynamics.

Its 2018 eruption caused destruction in residential areas but also created over 850 acres of new land along Hawaii’s coastline.

Kilauea has both summit and flank eruptions, with lava flows typically reaching the ocean and causing explosions of scalding steam and volcanic gases. But not all flank eruptions are destructive – in 1969-1974, flows mostly filled previously erupted craters.

Kilauea volcano’s nearly constant activity makes it a top attraction for volcano tourism and research.

Hualālai Volcano

The Hualālai volcano last erupted in 1801, sending flows downslope to the ocean in just 3 hours. This was only the 5th recorded eruption of Hualālai in written history. Standing at 8,271 feet elevation, scientists consider Hualālai dormant but not extinct.

Given the previous record of large eruptions every 200-500 years, Hualālai may erupt again within our lifetime.

Lava flow maps show an eruption today could threaten coastal communities and resorts on the volcano’s western flank. But scientists cannot yet accurately predict the next eruption window for Hualālai. Residents must live with the uncertainty and prepare emergency plans.

Extensive monitoring occurs to detect the first signs of unrest. Public education is also key – because the quiet volcano seems harmless, newcomers may not know the potential danger.

Dating the Big Island’s Origins

Radiometric Dating Techniques

Geologists use several radiometric dating techniques to determine the age of volcanic rocks from the Big Island of Hawaii. These methods measure the amount of radioactive isotopes and their decay products to calculate the time since the lava solidified.

One common approach is potassium-argon dating. This technique measures the decay of radioactive potassium-40 into argon-40 gas. Older rocks contain more argon gas built up over time. Using the known rate of decay, scientists can calculate an age.

Potassium-argon dates some of the oldest Big Island lava flows back over 400,000 years (USGS).

Another important method is paleomagnetic dating. As volcanic lava cools into rock, it captures a record of the earth’s changing magnetic field orientation. By matching field alignments in dated lava flows worldwide, geologists can assign estimated ages to Hawaii’s lava.

Combining radiometric and paleomagnetic dating gives the most reliable ages.

The Earliest Lava Flows

The earliest lavas exposed above sea level on Hawaii are over 400,000 years old. They built up the northern part of the island in the Kohala Volcano, which last erupted about 60,000 years ago (USGS).

However, drill samples from the ocean floor reveal that volcanic activity began building Hawaii island over 1 million years ago. These submarine lava flows now lie buried below younger flows or offshore under the Pacific Ocean.

The oldest known submarine section dates back about 1.15 million years (USGS).

Ongoing eruptions, erosion, wave action, and subsidence into the earth have erased much of the primitive early history of Hawaii island above and below the sea. But geologists continue to study lava samples using radiometric dating to piece together a record stretching back over a million years into the past.

Conclusion

As we have explored, the Big Island of Hawaii owes its existence to the volcanic hotspot located deep underneath it. The island’s three active volcanoes – Mauna Loa, Kilauea, and Hualalai – have been continuously erupting and adding new land over hundreds of thousands of years.

By utilizing radiometric dating of the oldest collected lava samples, geologists have determined that the Big Island emerged above sea level around 0.43 million years ago. The island continues to expand and evolve due to its volcanism.

This geological activity is part of the grand, ongoing story of how the Hawaiian archipelago came to be – one lava flow at a time.

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