/ Key Science Idea:
GEOLOGY
(say: gee-AH-la-gee)
the science of the Earth’s crust
WORD BANK

  • Basalt
(BAH-salt)
– dark gray to black rock with tiny crystals
  • Bog – swamp
  • Caldera
(cahl-DAIR-uh)
- huge crater with flat floor & steep sides
  • Carbon Dating
- finding age of something by the decay of carbon inside it
  • Cinder Cone
(SIN-der)
- cone shaped hill at crater’s side, & has own crater
WORD BANK
  • Erosion
(e-RO-zhun)
- wearing away of dirt or rock
  • Fossil Reef
- ridge of rock or coral in or near ocean with remains of ancient plants or animals embedded in it
  • Hotspot
- area of active,liquid, hot rock rising from deep in the Earth’s mantle
  • Rift Zone
- line of cracks & vents stretching from top of a volcano down its side to its base miles away
  • Shield Volcano
- broad, gently sloping volcano, tens of miles across, made of many thin lava flows /
(D. Saltzer)Eroded cliffs & lava flows on the Wai‘anae Volcano caldera. In back, Kamaile`unu & Lualualei mountains formed an ancient rift zone.
WAI‘ANAE IS ERUPTING!!!
Can you imagine a headline like this? This is what you would have read if people were around to write news stories millions of years ago.
HOW DO WE KNOW the WAI‘ANAERANGE was a VOLCANO?
There are hundreds of Hawaiian islands, atolls and sunken seamounts stretching across 1,000s of miles in the Pacific Ocean, but they all started at the same spot – above a hotspot! Even now, as you read this, your island is moving very, very slowly away from this underwater hotspot. Presently, the hotspot is below the BigIslandcausing eruptions and making a new island to the south. This new island already has a name: Lo‘ihi. When Lo‘ihi gets big enough, we will see its volcano, too. Every Hawaiian island was once made of one or more active volcanoes.
WHERE are the OLDEST LANDS on O‘AHU?
Scientists think that 3 to 4 million years ago a huge shield volcano rose up forming the leeward half of O‘ahu. If you hike to MountKa‘ala, you will find a big flat bog … this is the left over surface of the middle of an ancient caldera. This used to bejust like the Kilauea Caldera on the BigIslandnow, slowly filling with lava.
WHERE IS THE VOLCANO NOW? Look 50 to 70 miles away from shore & under water. At first, the land was so heavy it started to slowly sink into the ocean. But there was also a huge slide off Ka‘ena Point which must have caused a very sudden and enormous tsunami!
HOW KĀHUNA KNEW the AGE of the ISLANDS

Coral in the dry fossil reef at Kahe Point
Next time you go on a reef walk, look carefully at the ground. Like the Hawaiian scientists long ago, you can tell the land is very old and has seen many changes. Look at the photo and try to think like kāhuna did in the past.
Kāhuna kilo honua (geologists) knew coral only grows underwater & takes decades to get big. They knew waves, rain and wind take hundreds of years to wear down lava, and they knew volcanoes can make entire islands, but it happens in stagesand with different kinds of eruptions over time. The ancient chants kāhuna created eventell us which islands were formed first and last.
By using kāhuna logic, we can tell many things that happened to the shore at Kahe Point – long ago this shore was underwater, and before that it was formed by lava flows. This lava rock is different from the eruptions that made the smaller cinder cones above Kahe Point, but it is similar to the basalt type of rock found in the Lualualei mountains. So we know this reef is very old –older than its own hills!

Modern scientists study the geology of Earth the same waykāhuna did also use maps to help them see the “big picture”. This map shows the half that’s left of the huge volcano that once formed the coast of Leeward O‘ahu. Today we also use “carbon dating” to find out how old rocks are.

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Science in Hawai‘i:Nā Hana Ma Ka Ahupua‘a – A Culturally Responsive Curriculum Project Adapted from Roadside Geology of Hawai`i by Hazlett & Hyndman, 1996