The Formation and Composition of Volcanic Rocks in Iceland

Uncategorized By Mar 20, 2023

Iceland’s unique geological history has resulted in the formation of volcanic rocks that dominate the landscape, making up 90% of the land. The volcanic activity is caused by Iceland’s location on a hotspot, where magma rises from the earth’s mantle and creates volcanic activity on the surface. The volcanic rocks found in Iceland are mostly basaltic in composition due to the magma’s composition under Iceland. These rocks may form from basaltic eruptions, explosive eruptions, or subglacial eruptions that can cause significant hazards for people and the environment. Understanding the formation and composition of volcanic rocks in Iceland is vital for managing and minimizing volcanic hazards.


Iceland is a land of fire and ice with a unique geological history. Its rocky terrain is formed from volcanic activity due to its location on the Mid-Atlantic Ridge, where the North American and Eurasian tectonic plates meet. This article provides a brief insight into the formation and composition of the volcanic rocks in Iceland.

Formation of Volcanic Rocks in Iceland

Iceland is situated on a hotspot, which is an area where magma rises from deep within the earth and creates volcanic activity on the surface. The volcanic rocks that make up the island are formed through a variety of processes, including:

1. Basaltic Eruptions: The most common type of eruption in Iceland is basaltic. This type of eruption produces lava flows that spread out over the surface of the land. Basaltic eruptions are created by low viscosity lava that flows easily without creating significant explosions.

2. Explosive Eruptions: Explosive eruptions occur when magma rises to the surface, but the pressure builds up so much that it explodes, sending ash and debris into the air. These eruptions are less common in Iceland than basaltic eruptions but can still have severe consequences.

3. Subglacial Eruptions: In Iceland, many of the volcanoes are located under glaciers. When an eruption occurs under the ice, the heat melts the ice, and the resulting water mixes with the volcanic ash and forms massive floods known as jökulhlaups.

Composition of Volcanic Rocks in Iceland

The volcanic rocks found in Iceland are mainly basaltic in composition. Basalt is an igneous rock that forms from solidified lava flows under the Earth’s surface or on the surface of the Earth. Basalt is composed mainly of minerals such as pyroxene and plagioclase feldspar.

The dominant mineral in basalt is normally pyroxene, followed by plagioclase feldspar. Basalt may also contain olivine, quartz, hornblende, biotite mica, and magnetite. The lava of Iceland’s volcanoes is usually dark and dense, with a low viscosity that allows it to travel vast distances as lava flows.


1. Is Iceland entirely made up of volcanic rocks?

No, Iceland consists of both volcanic and non-volcanic rocks. The volcanic rocks dominate the landscape, making up 90 percent of land in Iceland.

2. Why are volcanic rocks in Iceland almost always basaltic?

The magma that rises through the mantle beneath Iceland is mostly basaltic in composition. This is because Iceland sits on a rift zone where divergent tectonic plate boundaries meet, allowing magma to rise to the surface, forming basaltic lava flows.

3. What are the hazards of volcanic activity in Iceland?

Eruptions and volcanic activity in Iceland can cause significant hazards to people and the environment. Lahars, ash clouds, and pyroclastic flows are just some of the hazards that may occur during an eruption.


Iceland’s volcanic rocks have a remarkable origin and a unique chemical composition. The basaltic lava flows from Iceland’s volcanoes form intricate and aesthetically pleasing landscapes. However, the volcanic activity also poses significant hazards to the population, and Icelanders must be continuously prepared for any eventuality. Nevertheless, understanding the formation and composition of volcanic rocks in Iceland is critical to managing and minimizing volcanic hazards.