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.