How Did Hawaii Form?

Summary

Hawaii's volcanic island chain, situated over a mantle plume, defies typical tectonic plate edge volcano formation. The hotspot, fueled by heated rock from Earth's core, causes rock to rise and form magma, which reaches the surface as lava. This basaltic lava creates volcanoes with gentle slopes and can lead to the formation of fissures. As the Pacific plate moves northwest, it drags the crust over the hotspot, creating new islands. The Big Island, Hawaii's youngest, hosts four active volcanoes and continues to evolve, with a new island, Loihi, expected to emerge in approximately 200,000 years.

Takeaways

• 🌋 Hawaii is formed by a mantle plume, not at the edge of a tectonic plate.
• 🔥 The island chain sits over a hotspot, which is a source of heated rock from the Earth's core.
• 📌 The solid rock at the bottom of the mantle rises and creates a bulge, leading to the formation of magma.
• 🌎 Magma rises through the crust's cracks, reaching the surface as lava.
• 💧 Hawaiian volcanoes produce more fluid lava from melted basalt compared to more explosive types.
• 🏞️ Basaltic lava creates volcanoes with gentle slopes and sometimes visible lava lakes at their summits.
• 🌊 When lava meets the ocean, it expands the island but creates dangerous hydrochloric acid steam.
• 🌀 The Pacific plate's northwest movement drags the crust over the hotspot, forming new islands.
• 🚀 The hotspot might also be moving, affecting the age and formation of the islands in the chain.
• 🗓️ The oldest volcanoes are on Niihau and Kauai, about 5 million years old, while the Big Island is the youngest at 400,000 years.
• 🔄 The Big Island continues to change with four active volcanoes and will eventually move off the hotspot, allowing a new island to form.
• ⏳ The next island, Loihi, won't break the ocean's surface for another 200,000 years.

Q & A

Why is Hawaii not near the edge of a tectonic plate but still has volcanoes?

Hawaii is located over a hotspot, which is fueled by a mantle plume of heated rock from the Earth's core, rather than being at the edge of a tectonic plate where most volcanoes are found.

What causes the formation of a bulge under the Earth's crust?

The hot rock from the Earth's core slowly rises and pushes up the crust, forming a bulge due to the buoyancy of the heated material.

How does magma form under the bulge?

Under the bulge, some of the rock melts into magma due to the intense heat from the rising hot rock.

What is the difference between magma and lava?

Magma is molten rock beneath the Earth's surface, while lava is magma that has reached the surface.

Why are Hawaiian volcanoes less explosive than others like Mt. Saint Helens?

Hawaiian volcanoes produce lava flows made of melted basalt, which is more liquid and less explosive than the lava produced by more explosive volcanoes.

What is the composition of Hawaiian lava flows?

Hawaiian lava flows are primarily composed of basalt, which is a type of volcanic rock that is less viscous and flows more easily.

What happens when lava from a Hawaiian volcano meets the ocean?

When lava meets the ocean, the island grows as the lava cools and solidifies. However, the interaction also produces steam that contains hydrochloric acid and volcanic glass.

How does the movement of the Pacific plate relate to the formation of the Hawaiian islands?

The Pacific plate is moving to the northwest, dragging the crust over the hotspot, which creates new islands as it goes.

How old are the oldest volcanoes in the Hawaiian island chain?

The oldest volcanoes, found on the islands of Niihau and Kauai, are about five million years old.

What is the youngest island in the Hawaiian chain and when did it start forming?

The Big Island of Hawaii is the youngest and started forming about 400,000 years ago.

How long will it take for the seamount Loihi to break the ocean's surface?

Loihi is expected to break the ocean's surface in another 200,000 years, give or take.

Outlines

00:00

🌋 Formation of Hawaiian Volcanoes

The script explains the unique formation of Hawaii's volcanic islands, which are not situated on the edge of a tectonic plate but over a hotspot. This hotspot is created by a mantle plume of heated rock from the Earth's core. As the hot rock rises, it melts some of the crust into magma, which then travels to the surface through crust cracks, forming volcanoes. The volcanoes produce more fluid basaltic lava, resulting in volcanoes with gentle slopes and sometimes visible lava lakes. The script also mentions the process of lava meeting the ocean, which expands the islands but releases dangerous steam. The movement of the Pacific plate over the hotspot and the potential movement of the hotspot itself are discussed, along with the age and formation timeline of the islands in the chain, highlighting the Big Island as the youngest and most active, with four active volcanoes.

Keywords

💡Hawaiian Islands

The Hawaiian Islands are a chain of volcanic islands in the Pacific Ocean, formed due to a unique geological process not typically associated with tectonic plate edges. In the video, it is explained that these islands are not near a tectonic plate edge, which is the usual site for volcanoes, but are instead formed over a hotspot, making them a key focus of the video's exploration into volcanic formation.

💡Hotspot

A hotspot in geology refers to a region of intense heat within the Earth's mantle that generates magma, leading to volcanic activity. The video highlights that the Hawaiian Islands are located over a hotspot, which is the driving force behind the formation of the island chain and its numerous volcanoes.

💡Mantle Plume

A mantle plume is a column of abnormally hot rock within the Earth's mantle that rises from deep within the planet towards the surface. The video script explains that the Hawaiian hotspot is fueled by a mantle plume, which is crucial for the formation of the volcanic islands.

💡Magma

Magma is molten rock found beneath the Earth's surface. The script describes how heated rock from the mantle rises and melts into magma beneath the crust, which then makes its way to the surface through cracks, forming volcanoes. Magma is the precursor to lava and is central to the volcanic activity discussed in the video.

💡Lava

Lava is magma that has reached the Earth's surface. The video explains that once magma breaches the surface, it is termed lava, which is the material that forms the Hawaiian volcanoes. The lava flows from Hawaiian volcanoes are described as being more fluid than those from more explosive volcanoes.

💡Basalt

Basalt is a type of rock that forms from rapidly cooling lava. The video mentions that Hawaiian volcanoes produce lava flows made of melted basalt, which is more fluid and results in volcanoes with gently sloping sides, contrasting with the steeper slopes of more explosive volcanoes.

💡Fissures

Fissures are cracks in the Earth's crust through which magma can rise to the surface. The video script describes how magma can sometimes flow underground to the sides of the main vent and erupt out of fissures, contributing to the growth and shape of the islands.

💡Hydrochloric Acid

Hydrochloric acid is a strong acid that can form when lava meets water, such as when it enters the ocean. The video mentions the steam produced when lava meets the ocean contains hydrochloric acid, which can be hazardous, highlighting the dramatic and sometimes dangerous interactions between volcanic activity and the environment.

💡Pacific Plate

The Pacific Plate is one of the Earth's tectonic plates. The video explains that the movement of the Pacific plate over the hotspot is responsible for the formation of the Hawaiian Islands as it drags the crust and creates new islands.

💡Niihau and Kauai

Niihau and Kauai are the northwesternmost islands in the Hawaiian chain. The video uses these islands as examples to illustrate the age progression of the islands, with Niihau and Kauai being the oldest at about five million years old, showcasing the geological timeline of the island formation.

💡Loihi

Loihi is an underwater volcano and the youngest part of the Hawaiian hotspot. The video mentions that Loihi will not break the ocean's surface for another 200,000 years, indicating the slow geological processes at work in the formation of new islands in the chain.

Highlights

Hawaii is situated in the middle of the Pacific Ocean, not near the edge of a tectonic plate where volcanoes are typically found.

The island chain is formed over a hotspot, driven by a mantle plume of heated rock.

Heated rock from the Earth's core rises slowly, creating a bulge in the crust.

Some of the rock melts into magma beneath the bulge.

Magma reaches the surface through crust cracks, becoming lava once above ground.

Hawaiian volcanoes produce more liquid basaltic lava flows compared to more explosive volcanoes.

Basaltic lava forms volcanoes with gently sloping sides, unlike more explosive volcanoes.

Active volcanoes like Kilauea can have a lake of liquid lava visible at the top.

Magma can flow underground and erupt through fissures on the sides of the main vent.

When lava meets the ocean, it can expand the island, but the steam is dangerous due to hydrochloric acid.

The Pacific plate's northwest movement drags the crust over the hotspot, creating islands.

The hotspot may also be moving, affecting the age of the volcanoes in the chain.

Niihau and Kauai, the oldest in the chain, have volcanoes about five million years old.

The Big Island of Hawaii is the youngest, with its formation starting about 400,000 years ago.

The Big Island is still changing with four active volcanoes.

As the Big Island moves off the hotspot, a new island will eventually form next to it.

Loihi, the next volcanic seamount, won't break the ocean's surface for another 200,000 years.

The transcript is from Scientific American, narrated by Kelsey Kennedy.

Transcripts

Hawaii sits in the middle of the Pacific Ocean, and nowhere near the edge of a tectonic plate

where volcanoes are usually found.

So how did the island chain form,

with all of its volcanoes?

The island chain is located over a hotspot

fueled by a mantle plume of heated rock.

Solid rock at the bottom of the Earth’s mantle is heated by the planet’s core.

That hot rock slowly rises and pushes up the crust, forming a bulge.

Under that bulge, some of the rock melts into magma.

Magma makes its way to the surface through cracks in the crust.

Once it’s above ground, it’s known as lava.

Hawaiian volcanoes produce lava flows made of melted basalt, which is more liquid than

lava produced by more explosive volcanoes like Mt. Saint Helens.

Basaltic lava flows form volcanoes with gently sloping sides.

A lake of liquid lava can sometimes be seen at the top of active volcanoes, like Kilauea.

[spraying sound] Sometimes the magma can flow underground to

the sides of the main vent and erupt out of cracks in the ground called fissures.

When lava meets ocean the island grows, but you may not want to get too close.

That steam is hydrochloric acid laced with tiny shards of volcanic glass.

The Pacific plate is moving to the northwest, dragging the crust over the hotspot and creating

islands as it goes.

The hotspot itself might be moving too.

The volcanoes on Niihau and Kauai, the northwesternmost islands in the chain, are about five million

years old.

The big island of Hawaii is the youngest and started forming about 400,000 years ago.

It’s still changing, and is home to four active volcanoes.

Eventually the big island will no longer be over the hotspot, and a new island will grow

next to it.

But maps won’t need updating for a while – Loihi won’t break the ocean’s surface

for another 200,000 years, give or take.

For Scientific American, I’m Kelsey Kennedy.

[music]