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📘 How does a volcano build an island?

Stand on Hawaiʻi’s youngest shore and look southeast: a submarine volcano is growing out of sight. Heat from the mantle melts rock beneath the moving Pacific Plate, while the plate carries older volcanoes away.

5
lessons
~25 min
to learn
Adults
level
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What you’ll learn

  1. A hotspot starts below the seafloorExplain how a persistent melt source and moving plate make a volcanic chain.Hotspot melting, rising basalt, and plate motion begin the island-building sequence.
  2. The plate makes a chainUse volcanic ages, alignment, and seamount shape as evidence for plate motion over a hotspot.A moving plate carries volcanoes away and assembles a young-to-old chain of islands and seamounts.
  3. Lava stacks a shield above the wavesConnect basalt flow behavior and overlapping layers with shield-volcano shape.Repeated fluid lava flows build a broad, layered volcanic island.
  4. The island enters a life cycleTrace volcanic extinction, erosion, cooling, and subsidence after plate motion.An island changes after it leaves the hotspot, even when its lava foundation remains.
  5. Coral preserves the volcanic outlineExplain the transition from fringing reef to barrier reef to atoll.Coral growth can preserve the outline of a volcanic island as the center subsides.

Questions this course answers

What makes a hotspot useful for explaining a volcanic island chain?

Plate motion carries older volcanoes away while new magma forms another above the source.

Put the early hotspot sequence in order.

Each step adds the next physical part of the volcanic edifice.

Why do repeated basalt flows make a broad shield volcano?

The profile records the low viscosity and repeated accumulation of basaltic lava.

Match each lava clue to what it records.

Textures and contacts preserve how lava moved and when a layer formed.

Put the idealized volcanic island life cycle in order.

The sequence links construction, isolation from the source, and later lowering.

Why can an old volcanic island be lower even if no sea-level change occurred?

The island can go down and lose height at the same time.

Grounded in trusted sources

  • U.S. Geological Survey, Geology of Hawai'i Volcanoes National Park, https://www.usgs.gov/geology-and-ecology-of-national-parks/geology-hawaii-volcanoes-national-park
  • U.S. Geological Survey Hawaiian Volcano Observatory, Evolution of Hawaiian Volcanoes, https://www.usgs.gov/observatories/hvo/evolution-hawaiian-volcanoes
  • U.S. Geological Survey, Volcanism in a Plate Tectonics Perspective, https://pubs.usgs.gov/gip/19/downloads/Appendixes/I_Volcanism%20in%20a%20Plate%20Tectonics%20Perspective.pdf
  • Koppers et al., Hotspot swells and the lifespan of volcanic ocean islands, Science Advances, https://pmc.ncbi.nlm.nih.gov/articles/PMC6938699/
  • NOAA Ocean Service, How a coral atoll forms, https://oceanservice.noaa.gov/education/tutorial_corals/media/supp_coral04a.html
  • Wikimedia Commons MediaWiki API, https://commons.wikimedia.org/w/api.php

Every Wunder lesson is built from real, reputable sources — never invented.

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