Lava Academy glossary: Key terms in geology and volcanology

Welcome to the Lava Academy by Lava Show! If you're reading about Icelandic volcanoes or attending our award-winning Lava Show, you've probably come across terms like "magma," "caldera," or "tectonic plate." But what do they all mean?

In this glossary, we break down the most important geology and volcanology terms in simple language, so you can understand the fascinating science behind volcanoes and the volcanic activity that shapes our world.

Glossary of Volcanology and Geology Terms

1. Lava

Lava is molten rock that erupts from a volcano and flows on the Earth’s surface. It's extremely hot—about 1,100°C (2,000°F) in our show! Once lava cools, it hardens into solid rock.

2. Magma

Magma is molten rock stored beneath the Earth's surface. When it erupts, it becomes lava. Think of magma as lava before it escapes the Earth.

3. Volcano

A volcano is an opening in the Earth’s crust where magma, gas, and ash escape. Volcanoes can form mountains and islands over time.

Þingvellir National Park in southwest Iceland offers a striking view of the Mid-Atlantic Ridge, where the North American and Eurasian tectonic plates visibly drift apart. This UNESCO World Heritage Site is rich in geological, cultural, and historical significance.

4. Tectonic Plates

These are massive slabs of rock that make up the Earth's surface. Iceland sits on the Mid-Atlantic Ridge where two plates—the North American and Eurasian plates—are pulling apart, causing frequent volcanic activity.

5. Mantle

The mantle is the thick, hot layer of rock beneath the Earth’s crust. Magma forms in the upper mantle and rises to the surface during eruptions.

6. Mantle Plume

A mantle plume is a column of super-heated rock rising from deep within the Earth. These plumes can cause volcanoes to form, as in the case of Grímsvötn volcano.

Víti, meaning "hell" in Icelandic, is a striking volcanic crater lake in the Krafla region of North Iceland. Formed during a 1724 eruption, its vivid blue waters and surrounding geothermal landscape make it a unique geological attraction along the country's volcanic routes.

7. Caldera

A caldera is a large, bowl-shaped depression formed when a volcano’s magma chamber empties and the surface collapses. Askja Volcano has a famous caldera lake inside it!

8. Crater

A crater is the bowl-shaped opening at the top of a volcano where eruptions occur. It’s smaller than a caldera and is often formed by explosive activity.

9. Eruption

An eruption is the release of magma, gas, and volcanic material from a volcano. Eruptions can be explosive or effusive (slow and flowing).

10. Ash Cloud

Volcanic ash is made of tiny fragments of rock and glass. During explosive eruptions, ash clouds can rise high into the atmosphere and disrupt air travel—something Iceland knows all too well.

11. Pyroclastic Flow

A fast-moving current of hot gas, ash, and volcanic rock that races down the sides of a volcano during an explosive eruption. It’s incredibly dangerous and moves at speeds over 100 km/h (60 mph).

Dimmuborgir, located near Lake Mývatn in northern Iceland, is known for its otherworldly lava formations and natural arches formed by ancient volcanic activity. This iconic site resembles a dark fortress and is steeped in Icelandic folklore, offering a striking landscape of twisted basalt structures and snow-dusted rocks.

12. Lava Tube

Lava tubes are tunnels formed by flowing lava that crusts over on top. When the lava drains, it leaves behind a hollow tube. These are often explored by cavers in Iceland.

13. Basalt

Basalt is a type of volcanic rock commonly formed from lava flows. Iceland’s dramatic black landscapes are largely made of basalt.

14. Fissure

A fissure is a long crack in the Earth’s surface where lava can erupt, often forming new land. Iceland’s famous 2014 Holuhraun eruption came from a fissure linked to Bárðarbunga.

15. Subglacial Volcano

A subglacial volcano erupts beneath a glacier. The heat melts the ice, often leading to massive floods called jökulhlaups.

16. Jökulhlaup

An Icelandic word describing a sudden, powerful flood caused by volcanic activity melting glacier ice. These floods can reshape landscapes in hours.

Strokkur geyser, one of Iceland’s most famous geothermal attractions, erupts every few minutes in the Haukadalur Valley. Surrounded by curious visitors, this natural phenomenon showcases the country’s intense geothermal activity and is a highlight of the Golden Circle route.

17. Geyser

A geyser is a hot spring that periodically erupts with steam and boiling water. While not a volcano, geysers are part of geothermal activity and common in volcanic regions like Iceland.

18. Geothermal Energy

Heat from beneath the Earth's surface used to generate electricity and hot water. Iceland relies heavily on this clean energy source, thanks to its volcanic activity.

19. Seismic Activity

This refers to movements in the Earth’s crust, including earthquakes. Increased seismic activity can signal that a volcanic eruption is near.

20. Geologist

A geologist is a scientist who studies the Earth—its materials, structure, processes, and history. Geologists investigate everything from rocks and minerals to earthquakes and volcanoes. They help us understand how landscapes form, how natural resources develop, and how Earth changes over time. At Lava Show, many of our expert presenters are trained geologists who bring deep knowledge and passion to the experience.

At Lava Show, guests witness real molten lava up close as a Lava Master expertly explains its properties and movement. This one-of-a-kind live demonstration combines science, storytelling, and spectacle, offering a thrilling and educational volcanic experience in Iceland.

21. Volcanologist

A volcanologist is a type of geologist who specializes in studying volcanoes, lava, magma, and related geological phenomena. They analyze eruption patterns, monitor active volcanoes, and often work in the field during volcanic events. Our Lava Masters often have formal training in volcanology or related fields.

Why these concepts matters

Understanding these terms helps you make sense of the incredible geological activity that shapes our world. At Lava Show, we bring many of these concepts to life—literally—with a real lava pour, expert storytelling, and hands-on education. Whether you’re a curious traveler or a budding scientist, learning the language of volcanoes deepens your appreciation of the natural forces shaping our world.