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Oahu and Kauai Volcanoes?

Ask the Big Kahuna

“Answering the most common visitor questions”


We will be visiting your state this summer and have a question for you.

Our daughter (fifth grade) has to do a school project for science, and we encouraged her to do one that ties in with our vacation. Her class will be studying volcanoes this spring, and she wants to do something on that.

Our problem is that we will be staying on Oahu and Kauai, not on the Big Island with the volcanoes. Is there anything she can do with volcanoes on islands that don’t have them?

Ed and Valerie


Aloha, Ed and Valerie!

Mahalo for writing.

Although they do not have active volcanoes today, Oahu and Kauai once did. Each of the Hawaiian islands was built by volcanoes that grew from the ocean floor.

How the Hawaiian islands came about could be a great project, and your daughter could gather evidence of the process on any island. The Kilauea Lighthouse on Kauai has an excellent 3-D map of the islands from the ocean floor up – a good place to start.

At some places under the earth’s crust, superhot magma from the mantle flows upward in a convection current like boiling water and pushes up against the crust. Those places are called “hot spots.” In the middle of the Pacific is such a spot.

The Pacific Plate, a huge slab of the earth’s crust, slides slowly toward the northwest over the “hot spot,” which pushes through the crust from time to time and makes a volcanic island. The crust moves on and takes the new island with it away from the hot spot.

It’s slow work though. Kauai was formed over the spot more than 5 million years ago.

Right now, the “hot spot” is under the southeast corner of the Big Island, where the active volcanoes are, and extends at least 20 miles offshore farther to the southeast, where a new island, already named Loihi, has begun to rise from the seabed. It’s still 1,000 meters below the surface of the water, though.

A quick trip to a bookstore on Kauai or Oahu should give you plenty of material on this fascinating subject. Specifically, see if you can find Hazlet and Hyndman’s Roadside Geology of Hawaii. Their approach literally puts you right on the road showing you details easily accessible as you drive around each island. The chapters on Oahu and Kauai have more than enough to fuel a report for the fifth grade. Plenty of photos, too.

Have a great visit and good luck with the report!

Big Kahuna