First thing first. This is how to pronounce Eyjafjallajökull. This is how to not pronounce it. Now on to the cache....
Volcanic Types
Volcanoes take many different forms, shaped by the style of eruption and the environment around them. From the broad shields of Hawai‘i to Iceland’s table mountains and island-building blasts at sea, each type tells a different story of how magma meets the surface. Below are the main types of volcanoes, with examples from Iceland and beyond.
Shield Volcanoes
Shield volcanoes are wide and gently sloping, built by countless flows of runny, fluid lava that spreads far before cooling. They resemble a warrior’s shield lying on the ground. The largest volcano in the world, Mauna Loa in Hawai‘i, is a classic example. In Iceland, shield volcanoes are less dramatic in height but cover vast areas of the central highlands, creating broad lava plains.
Stratovolcanoes (Composite Volcanoes)
Stratovolcanoes are steep-sided and dramatic, built from alternating layers of lava, ash, and rock fragments. Their eruptions can be both effusive and explosive. Eyjafjallajökull, the mountain before you, is a classic stratovolcano. Its glacier-topped cone hides a caldera at the summit. When it erupted in 2010, melting ice interacted with magma, producing powerful ash clouds that disrupted air travel across Europe. Nearby, Snæfellsjökull on the west coast is another iconic Icelandic stratovolcano.
Cinder Cones
Cinder cones are the simplest volcano type: small, steep piles of ash, cinders, and lava fragments ejected from a single vent. They are often short-lived and may appear on the flanks of larger volcanoes.
In Iceland, numerous small cones dot lava fields, especially in areas of fissure eruptions, such as around Lake Mývatn.
Lava Domes
Lava domes form when thick, sticky lava oozes slowly upward and piles over the vent instead of flowing far. The result is a rounded, steep-sided mound. A good example in Iceland is the postglacial lava domes around Hekla volcano, while worldwide examples include the dome that grew inside Mount St. Helens after its 1980 eruption.
Calderas
A caldera forms when a volcano erupts so violently that its magma chamber empties, causing the summit to collapse into a vast depression. These can later fill with water or ice. Eyjafjallajökull itself has a summit caldera about 2.5 km wide, now largely hidden beneath its glacier. To the east, Askja is a striking Icelandic caldera that holds a deep lake.
Subglacial Volcanoes & Tuyas
Unique to glaciated regions, subglacial volcanoes erupt beneath ice sheets. Magma melts cavities in the ice, and explosive interactions with meltwater produce glassy ash deposits called hyaloclastite. If the eruption breaks through to the open air, the lava may spread out to form a flat-topped, steep-sided mountain known as a tuya. The volcano Katla, just east of Eyjafjallajökull, sits beneath the Mýrdalsjökull glacier and is one of Iceland’s most dangerous subglacial volcanoes. Another striking example is Herðubreið, a table mountain (tuya) in the central highlands.
Submarine & Surtseyan Volcanoes
Most of Earth’s volcanoes are hidden beneath the oceans, where eruptions quietly build seamounts. But in shallow water, when rising magma meets the sea, the story changes. Explosive water–magma interaction produces violent Surtseyan eruptions, named after Surtsey, the volcanic island born just south of here in 1963. Over three years, Surtsey grew from the seafloor into a new island, providing a living laboratory for volcanologists and biologists alike.
🌍 At This Location
Here at Eyjafjallajökull, you stand before a glacier-clad stratovolcano. Its steep profile, layered slopes, and summit caldera reveal its history of repeated eruptions. Look southward and you are gazing toward the sea, where Surtsey rose less than a human lifetime ago. And to the east, under Mýrdalsjökull, lies Katla, a true subglacial giant. Together, these landscapes show the diversity of volcanoes—on land, under ice, and beneath the sea.
✅ Logging Tasks (message the answers to the CO)
- Eyjafjallajökull is a stratovolcano. From your viewpoint, describe two features you can see that support this classification.
- Estimate the steepness of the visible slopes (gentle, moderate, or steep). How does this match the expected slope of a stratovolcano?
- Explain why Eyjafjallajökull is not a subglacial volcano, even though it has a glacier on top.
- Looking south, describe how a Surtseyan eruption at sea (like Surtsey) would build a different shape than the icy cone in front of you.
Optional: Post a photo of yourself or your GPS at the viewing site, but please do not reveal your answers.
https://www.merriam-webster.com/dictionary/shield%20volcano
https://www.merriam-webster.com/dictionary/shield%20volcano
https://en.wikipedia.org/wiki/Shield_volcano
https://www.nps.gov/articles/000/shield-volcanoes.htm
https://en.wikipedia.org/wiki/Tuya
https://www.worldatlas.com/articles/volcanic-landforms-what-is-a-tuya.html
https://www.wired.com/2012/03/eruptions-word-of-the-day-tuya-eruptions-revisited
https://en.wikipedia.org/wiki/Subglacial_volcano
https://amazingiceland.is/destination/thorvaldseyri-farm/