SCIENCE

Tamu Massif, a volcano the size of New Mexico, has been identified under the Pacific Ocean, about 1,600 kilometers (1,000 miles) east of Japan, making it the biggest volcano on Earth and one of the biggest in the solar system. (National Geographic News)

Use our resources to better understand Tamu Massif and undersea geology.

Discussion Ideas

• Look at our beautiful high-resolution map of “Earth’s Dynamic Crust.” Use the zoom feature (+) to find Shatsky Rise (“Shatskiy” on the map), where Tamu Massif is located. (It’s between the Japan and Midway Island.) What other features of undersea geology surround Shatsky Rise and Tamu Massif?
  • A lot! The Japan and Kuril trenches lie to the west, while the Emperor Seamounts, Hess Rise, and Hawaiian Islands lie to the east.

• On the same map, use the zoom features to read the text at the bottom of the page. The text describes the six major ways volcanoes and earthquakes form: seafloor spreading, subduction, collision, faulting, accretion, and hot spots. Which of these processes probably contributed to the formation of Tamu Massif?
  • According to the NG News article, scientists are still working that out. (See the short, final section, “How Did the Volcano Form?”) Tamu Massif is part of a very tectonically complex area.
    • Subduction? Collision? 145 million years ago, the volcano sat on a “triple junction”—the boundary of three tectonic plates. We’re not quite sure how the plates interacted, because two of those plates, the Farallon and Izanagi plates, have long since subducted beneath the North American plate. Today, Tamu Massif sits entirely on the massive Pacific plate.
    • Hot Spots? The same process that created the Hawaiian Islands (home to the world’s second-largest volcano, Mauna Loa) may have created Tamu Massif. “[T]he amount of magma that had to go through the lithosphere [crust] is off the charts,” according to one scientist.

• Watch our “media spotlight” video on “Hawaii Geology.” In it, legendary explorer Robert Ballard explores Loihi, Hawaii’s newest volcano. What are some similarities and differences between Loihi and Tamu Massif?
  • Similarities:
    • They’re both seamounts, or underwater mountains.
    • They’re neighbors in the North Pacific Ocean.
    • They’re both shield volcanoes, created from lava flows (not explosive eruptions).
  • Differences:
    • Loihi is actively forming, while Tamu Massif has been inactive for more than 145 million years.
    • Loihi has a classic seamount shape—it looks like a steep, underwater mountain. Tamu Massif has a very gentle slope (near the summit, the slope is only one degree), which is why it was “hiding in plain sight” for millions of years.
    • Loihi is part of an easily recognizable chain of volcanic mountains—the Hawaiian Islands. Tamu Massif is the remains of a single, gigantic volcano.
    • Loihi will eventually be a part of an island (the “Big Island” of Hawaii, where its big sisters Mauna Loa and Kilauea currently dominate the volcanic landscape). The summit of Tamu Massif is about 2,000 meters (6,500 feet) below the ocean surface, and was never an island.