The Horseshoe Around the Pacific
One belt of trenches and volcanoes wraps three sides of the Pacific. It runs about 40,000 km. Almost every great earthquake on record happened somewhere along it.
of the planet’s largest earthquakes happen on the circum-Pacific belt, according to the USGS.
Read it as a horseshoe. The open end faces the Indian Ocean, and the Pacific plate sinks beneath the glowing line on almost every side.
Four in five giants, one belt
Earthquakes cluster where plates meet. The biggest ones cluster where an ocean plate dives under another plate, and that happens mostly around the Pacific.
Share of the world’s largest earthquakes by seismic belt · USGS
The Alpide belt runs from Java through the Himalaya to the Mediterranean. It is the only other belt that comes close, with about 17%. Mid-ocean ridges like the Mid-Atlantic produce many quakes, but almost never giant ones.
Giant quakes need a long, locked subduction fault that slips all at once. The Pacific rim is lined with them, from Chile to Alaska to Japan to Tonga.
Every quake of M8.7 or larger since 1900 sits on this map
Each whole step in magnitude releases about 32× more energy, so the gaps between these quakes are bigger than the numbers suggest. Valdivia 1960 released about 16 times the energy of the smallest quake on this list.
Energy relative to M8.7 Rat Islands 1965, computed from USGS magnitudes using the ~32×-per-unit rule (derived). *Sunda Arc.
Year vs. magnitude · USGS list of largest earthquakes since 1900. Dashed circle = Sunda Arc.
The ring is also the deepest water on Earth
Where a plate sinks, the seafloor bends down into a trench. Every one of the ocean’s deepest points lies on the Ring of Fire. Several are deep enough to hold Everest with more than a kilometre of water to spare.
Gold dots = Five Deeps 2019 measurements · white dots / “~” = widely cited approximate values · Everest: 2020 Nepal–China survey
A chain of 452 vents
Sinking plates carry water down with them. The water melts the mantle above, and the magma rises to build the volcanic arcs: the Andes, the Cascades, Japan’s Fuji, the Philippines’ Pinatubo.
volcanoes strung along the horseshoe
National Geographicof Earth’s active volcanoes sit on the ring
National GeographicPinatubo 1991 was the second-largest eruption of the 20th century
USGSWhat a slip on the line costs
Many of the world’s biggest coastal cities sit on or near the ring: Tokyo, Manila, Jakarta, Lima, Santiago, Los Angeles, Seattle.
deaths in the M9.5 Valdivia quake, 1960, still the largest ever recorded
USGSdead or missing after the M9.1 Tōhoku quake and tsunami, 2011
Japan NPApeak global cooling after Pinatubo, 1991, from ~20 Mt of SO₂
USGSWhy it matters
- It’s a horseshoe, not a ring. The line wraps the Pacific on three sides and leaves the Indian Ocean side open. The dashed Sunda Arc is often added to it.
- The trenches hug the coasts. Every teal triangle sits just offshore of a volcanic arc. The trench and the arc are two results of the same sinking plate.
- The big circles are all on the line. Circle area shows energy. Valdivia’s circle is 16 times the area of Rat Islands’.
- California is different. There the boundary is a sideways-sliding transform fault, the San Andreas. It produces strong quakes, but not M9 ones.
Sources & notes
- USGS, “Where do earthquakes occur?” (Earthquake Hazards FAQ): about 81% of the world’s largest earthquakes occur on the circum-Pacific belt; the Alpide belt accounts for about 17%. The ~2% “everywhere else” is the arithmetic remainder (derived).
- National Geographic Education, “Ring of Fire” encyclopedic entry: ~40,000 km horseshoe; 452 volcanoes; about 75% of Earth’s active volcanoes.
- USGS, “20 Largest Earthquakes in the World since 1900” (list updated after the 29 Jul 2025 Kamchatka M8.8): magnitudes and dates of the nine largest events. *Sumatra 2004 sits on the Sunda Arc, which many maps (and the dashed line here) treat as the Ring’s western extension.
- USGS, “How much bigger is a magnitude 8.7 earthquake than a magnitude 5.8?” (Earthquake Hazards FAQ): each whole magnitude step releases about 32× more energy. Energy ratios on this page are computed from that rule (10^(1.5·ΔM)), so they are derived, not measured.
- USGS, M9.5 Valdivia, Chile, 22 May 1960 event summary: 1,655 deaths, the largest earthquake instrumentally recorded.
- National Police Agency of Japan, Great East Japan Earthquake damage tally (2021): about 15,900 deaths and about 2,500 people still missing: more than 18,000 dead or missing.
- Five Deeps Expedition, 2019 sonar/dive depths (Stewart & Jamieson, Earth-Science Reviews, 2019): Challenger Deep 10,928 m (max dive depth), Horizon Deep 10,823 ± 10 m, Scholl Deep ≈10,003 m (preliminary). Emden Deep ~10,540 m, Kuril–Kamchatka ~9,600 m, Richards Deep ~8,065 m and Aleutian ~7,679 m are widely cited approximate values (marked ~).
- USGS, “The Cataclysmic 1991 Eruption of Mount Pinatubo” (Fact Sheet 113-97) and USGS Yellowstone FAQ on climate: second-largest eruption of the 20th century; ~20 million tonnes of SO₂; peak global surface cooling ~0.7 °C, lasting about three years.
- Nepal & China joint survey, 2020: Everest height 8,848.86 m (rounded to 8,849 m).
- Map note: the map is hand-simplified and schematic (Pacific-centred equirectangular, coastlines approximated). Plate boundaries are drawn to show the pattern, not exact positions. Quake epicentres approximate; circle area ∝ relative energy.