# Fissure Flames (DD-645) > A fissure eruption happens when a dike, a vertical sheet of magma forced up through the crust, reaches the surface along a crack. Lava then erupts from many points along a line at once, often as a row of lava fountains that the USGS calls a 'curtain of fire'. Most fissure eruptions involve runny basalt and are effusive, meaning lava pours out rather than exploding. The National Park Service rates them at 0 to 1 on the Volcanic Explosivity Index. So the main products are lava fountains, spatter and gas, not big ash columns. Spatter piling up along the crack builds low ramparts and spatter cones, so a fissure can leave a row of small craters rather than one tall cone. Fissures range from a few hundred meters to tens of kilometers long. Iceland's Laki (Lakagígar) eruption began on June 8, 1783, from a fissure system about 27 km long with more than 130 craters. Feeder dikes for the Columbia River flood basalts reach as much as 180 km. Fissure eruptions are common where plates pull apart, as in Iceland, which sits on the Mid-Atlantic Ridge. They also happen along rift zones on the flanks of hot-spot shield volcanoes like Kīlauea and Mauna Loa, and in volcanic fields in the middle of continents. The footage shows a line of lava fountains beside a gas plume, with a fresh lava field on either side. The source doesn't name the eruption, so the case doesn't either. - Department: Nature (also Science) - First published: 2025-08-30 - Last updated: 2025-08-30 - Permalink: https://detailenjoyer.com/case/fissure-flames/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## On the timeline - **June 8, 1783**: The Laki fissure eruption begins in Iceland Full timeline: https://detailenjoyer.com/timeline/?case=fissure-flames ## Quick facts - **DD-645-F01**: Fissure eruptions are mostly effusive. _(Write-up · Exhibit C (Mostly lava, not ash))_ - **DD-645-F02**: Laki's fissure system is about 27 km long. _(Write-up · Exhibit D (Laki, 1783))_ ## Write-up Volcanoes that unzip. Fissure eruptions pour lava from cracks kilometers long. 1. **How a fissure opens**: A vertical sheet of magma called a dike reaches the surface along a crack, and lava erupts from many points at once. 2. **Curtains of fire**: Runny basalt fountains up along the line, and spatter builds low ramparts and cones beside the crack. 3. **Mostly lava, not ash**: Most fissure eruptions are effusive, scoring 0 to 1 on the Volcanic Explosivity Index. 4. **Laki, 1783**: Iceland's Laki eruption began on June 8, 1783, along a fissure system about 27 km long with more than 130 craters. 5. **Not only where plates part**: Fissures also open along rift zones on hot-spot volcanoes like Kīlauea and Mauna Loa. ## Related case files - [Doom Plume (DD-636)](https://detailenjoyer.com/case/doom-plume/): The explosive side of volcanoes - [Danakil Depression (DD-055)](https://detailenjoyer.com/case/danakil-depression/): Volcanic ground where plates are pulling apart - [Liquid Rock (DD-298)](https://detailenjoyer.com/case/liquid-rock/): I paired it with how fissure eruptions happen - [Hallgrímskirkja (DD-567)](https://detailenjoyer.com/case/hallgrimskirkja/): Iceland's volcanic geology, the source of its basalt - [Kawah Ijen (DD-600)](https://detailenjoyer.com/case/kawah-ijen/): Another volcano case ## Reel vs. record - **Note**: 'Magma, gas, and ash erupt': most fissure eruptions are effusive, made of lava fountains, spatter and gas. Significant ash comes mainly when water or more explosive magma is involved. - **Note**: 'Instead of centralized volcanic cones': fissures don't build one big cone, but spatter can pile up into ramparts and rows of small spatter cones and craters. Laki left more than 130. - **Note**: 'Several kilometers': often true, but they can be far longer. Laki's fissure system is about 27 km, and Columbia River basalt feeder dikes reach about 180 km. - **Note**: 'Where tectonic plates are pulling apart': common there, as in Iceland, but fissures also open in rift zones on hot-spot shield volcanoes like Kīlauea and Mauna Loa, which aren't on a plate boundary. - **Note**: 'Mid-ocean ridges': most mid-ocean ridge fissure eruptions happen deep underwater. Iceland is one of the few places where the ridge is above sea level. ## Video: Fissure Flames: Volcanoes That Unzip - Duration: 18.5 s · Published: 2025-08-30 - File: https://detailenjoyer.com/assets/videos/DN-7JQykTbX.mp4 ### Transcript DID YOU KNOW? Volcanic fissures are long cracks in the Earth's crust through which magma, gas, and ash erupt, often forming dramatic linear vents instead of centralized volcanic cones. These fissures can stretch for several kilometers and occur where tectonic plates are pulling apart, such as along mid-ocean ridges or rift zones. NOW YOU KNOW! ## Questions & answers **Q: What usually feeds a fissure eruption?** A: A vertical sheet of magma reaches the surface along a crack. _(Source: Write-up · Exhibit A (How a fissure opens) · U.S. National Park Service: Fissure volcanoes; USGS California Volcano Observatory (Jul 11, 2023): Fall into a burning (curtain) of fire with fissure eruptions)_ **Q: What does the USGS call a line of lava fountains along a fissure?** A: Runny lava fountains up along the crack. _(Source: Write-up · Exhibit B (Curtains of fire) · USGS California Volcano Observatory (Jul 11, 2023): Fall into a burning (curtain) of fire with fissure eruptions)_ **Q: How explosive are most fissure eruptions?** A: Lava pours out rather than exploding. _(Source: Write-up · Exhibit C (Mostly lava, not ash) · U.S. National Park Service: Fissure volcanoes)_ **Q: About how long is Laki's fissure system?** A: With more than 130 craters. _(Source: Write-up · Exhibit D (Laki, 1783) · Britannica: Laki; Katla UNESCO Global Geopark: Lakagígar)_ **Q: Which Hawaiian volcano has rift-zone fissure eruptions?** A: Kīlauea and Mauna Loa have active rift zones. _(Source: Write-up · Exhibit E (Not only where plates part) · U.S. National Park Service: Fissure volcanoes; USGS Volcano Watch: Getting in the (rift) zone, why and how they erupt)_ ## Sources - [U.S. National Park Service: Fissure volcanoes](https://www.nps.gov/articles/000/fissure-volcanoes.htm) - [USGS California Volcano Observatory (Jul 11, 2023): Fall into a burning (curtain) of fire with fissure eruptions](https://www.usgs.gov/observatories/calvo/news/fall-a-burning-curtain-fire-fissure-eruptions) - [USGS Volcano Watch: Getting in the (rift) zone, why and how they erupt](https://www.usgs.gov/news/volcano-watch-getting-rift-zone-why-and-how-they-erupt) - [Britannica: Laki](https://www.britannica.com/place/Laki) - [Katla UNESCO Global Geopark: Lakagígar](https://www.katlageopark.com/geosites/mainly-geology/lakagigar/) ## Cite this case file Easterling, Marcus. "Fissure Flames." The Detail Department (DetailEnjoyer), case file DD-645, last updated Aug 30, 2025. https://detailenjoyer.com/case/fissure-flames/