A Journey Into the Earth: 5 Geosites in West Iceland

The West region of Iceland, often nicknamed "Miniature Iceland," features a diverse array of the country's signature geological wonders. This compact area includes glaciers, glacial rivers, volcanoes, waterfalls, lava fields, basalt columns and lava tube caves, offering a unique opportunity to peek inside the earth.

West Iceland can be divided into two main areas: Borgarfjörður and the Snæfellsnes Peninsula. For those driving from Reykjavík, the scenic route along Hvalfjörður (the Whale Fjord) is recommended, with its dramatic landscapes and numerous dykes.

Borgarfjörður is characterized by its diverse geological features, including the Borgarfjörður Anticline, formed by the rift jump from the Snæfellsnes Peninsula to the Reykjanes Peninsula 6-7 million years ago. The bedrock in this area dates back to the Tertiary period, around 6-12 million years ago, and is marked by basaltic lava flows and glacial remains from the last Ice Age. The Silver Circle, a popular tourist route, offers a glimpse into the region's geothermal activity, waterfalls, and historic sites.

Snæfellsnes Peninsula is often referred to as "Iceland in a nutshell" due to its varied geological formations. The peninsula showcases a range of features, with the Snæfellsjökull ice-capped stratovolcano sitting as a crown on the westernmost point. The bedrock here was formed in two phases: in the old rift zone in Hnappadalur, active 7-14 million years ago, until the rift jump; and 1-2 million years ago when volcanism reappeared, an enigma with no concrete explanation. Three active volcanic systems are found here: Ljósufjöll, Lýsa, and Snæfellsjökull, collectively forming the Snæfellsnes Volcanic Zone (SVZ). The Snæfellsjökull stratovolcano has been dormant since 200 AD but has experienced volcanic episodes approximately every 2,000 years. The most recent volcanic activity occurred in the 12th century in the Ljósufjöll system. In recent years, Ljósufjöll has exhibited increased earthquake activity, which may be a preliminary sign of unrest.

1. Hraunfossar Waterfalls: The Interplay of Water and Substrate

Location: Hraunfossar waterfalls are located in the Borgarfjörður region and are easily accessible via Route 518, which leads from the town of Borgarnes towards the interior highlands. See Hraunfossar car park on a map.

Hraunfossar (Lava Waterfalls) is a one-of-a-kind series of waterfalls that emerge from beneath the Hallmundarhraun lava field, cascading into the Hvítá River (White River). This natural wonder showcases a distinct interaction between the crystal-clear spring water of the falls and the glacial meltwater of Hvítá, highlighting the diverse hydrological processes in the area. Nearby, the cascades of Barnafoss illustrate how the Hvítá river erodes the edges of the lava field, creating a network of gullies and natural stone arches through erosion, especially during flood events.

The origin of Hraunfossar dates back to an eruption in the early 10th century near the edge of the Langjökull icecap, leading to the formation of the Hallmundarhraun lava flow. This significant lava deposit altered the landscape and the course of the Hvítá river, providing insights into postglacial volcanic activity in Borgarfjörður. The porosity of the Hallmundarhraun lava field facilitates the percolation of rainwater, preventing the formation of surface rivers but enabling groundwater streams to surface at Hraunfossar. This process is specific to the site due to the underlying impermeable rock layers that force groundwater to emerge along the edge of the lava field, creating waterfalls.

Geological features near Barnafoss, include a series of lava layers and a light-brown dyke. The dyke, a relic of the ancient Húsafell central volcano active millions of years ago, provides a visual contrast and a link to the region's volcanic past. These features illustrate an unconformity in the geological record, where layers of rock do not align in a continuous sequence, indicating periods of erosion or other geological processes that have removed layers. This offers a practical example of how geological histories are understood, making Hraunfossar a valuable site for understanding Iceland's complex geological framework. Other noteworthy geological features include the visible lava ropes in the area across the bridge.

For a complete experience, visitors should also stop by Deildartunguhver, one of the world's most prolific hot springs, and enjoy the relaxing Krauma nature baths or the nearby Secret baths.

Lava tubes are common geological features in Iceland but rare globally, making them a must-visit for geology enthusiasts. Photo credit: Ægir Þór Þórsson.

2. Víðgelmir and Vatnshellir: The Lava Tube Twins of West Iceland

Lava tube caves are fascinating geological formations created in effusive eruptions where basalt magma is involved. While rare globally, they are quite common in Iceland so travelers should not miss the opportunity to explore this unique type of caves. For those familiar with limestone caves, lava tubes offer a completely different experience, yet with many similarities. We leave it to you to discover what that entails on your own.

West Iceland offers two excellent examples that are accessible and can be safely explored through guided tours; Víðgelmir in upper Borgarfjörður area and Vatnshellir in Snæfellsjökull National Park. Please note that access to these caves is only possible through guided tours for safety and conservation purposes.

Víðgelmir Cave

Víðgelmir cave, located in the Hallmundarhraun lava field near the village of Húsafell, is one of the largest and best-preserved lava tube caves in Iceland. Extending approximately 1.6 kilometers, Víðgelmir features a variety of lava formations including stalactites, stalagmites, and other notable features. The cave is also an important archaeological site with artifacts dating back to the Viking Age. For detailed information on booking a cave tour, visit TheCave.is.

Vatnshellir Cave

Vatnshellir Cave, situated on the Snæfellsnes Peninsula within the boundaries of Snæfellsjökull National Park, offers a significant example of lava tube geology. The cave descends about 35 meters below the surface and extends for roughly 200 meters. Guided tours of Vatnshellir navigate through its passages, highlighting the geological processes responsible for its formation. These tours also discuss the cave’s relationship with the Snæfellsjökull glacier and volcano, which served as an inspiration for Jules Verne's novel "Journey to the Center of the Earth." For more information and cave tour booking visit Summitguides.is.

Formation of Lava Tube Caves

The process of forming a lava tube cave involves several key stages:

1. Eruption and Lava Flow: During a volcanic eruption, basaltic lava flows out of a volcano's vent and spreads across the landscape. The outer surface of the lava flow begins to cool and solidify upon contact with the air and the surface, forming a crust.

2. Insulation and Tube Formation: As the outer crust cools and hardens, the interior of the lava flow remains molten and continues to flow beneath the insulating crust. This creates a conduit or tunnel through which the molten lava travels.

3. Continued Flow and Drainage: The molten lava continues to flow through the tube, often for many kilometers. Over time, the source of the lava may diminish or cease entirely, causing the molten lava within the tube to drain out. This drainage leaves behind an empty, hollow tube - essentially a natural underground tunnel.

4. Cooling and Solidification: The interior of the lava tube cools and solidifies, forming the walls and ceiling of the cave. These structures can exhibit various features such as smooth, glassy surfaces, rope-like textures (known as pahoehoe), and lava stalactites and stalagmites formed from dripping lava.

5. Secondary Features: Over time, additional features may develop within the lava tube cave. These can include formations created by subsequent lava flows, mineral deposits, and breakdown materials from the cave ceiling and walls.

The Grábrók area serves as an outdoor laboratory for studying typical fissure eruption formations and plant succession.

3. Grábrók: A Trio of Scoria Craters Created in a Fissure Eruption

Location: Grábrók is located in the Borgarfjörður region of West Iceland, near the town of Bifröst. Ring Road No. 1 bends around the crater, making it easily accessible. Staircases have been built for an easy hike to the top of the main crater, and hiking paths extend around the area, passing by the two smaller craters. A a map of the area is available for visitors.

Grábrók is a prominent volcanic crater located in the Borgarfjörður region of West Iceland, near the town of Bifröst. As part of the Ljósufjöll volcanic system, Grábrók, along with the smaller craters Grábrókarfell and Smábrók, presents a great opportunity for geological exploration and education. The area was declared as a nature conservation area in 1962.

Grábrók was formed approximately 3,800 years ago in a fissure eruption. Unlike central vent eruptions, fissure eruptions occur when magma rises through a crack or fissure in the Earth's crust, creating a series of craters along the fissure line. This type of volcanic activity is characteristic of the tectonic and volcanic dynamics of Iceland, where the Mid-Atlantic Ridge creates numerous fissure systems. The current events on Reykjanes peninsula are comparable.

The eruption that created Grábrók produced a large amount of basaltic tephra—volcanic ash, lapilli, and volcanic bombs—that settled to form the well-defined craters we see today. Basalt, a common volcanic rock in Iceland, forms from the rapid cooling of low-viscosity lava rich in magnesium and iron. The layers of tephra at Grábrók showcase the different phases of the eruption and the varying intensity of volcanic activity.

From the top of Litla-Grábrók, visitors can enjoy a panoramic view that includes Baula, a pointy light-colored rhyolite mountain in the northwest. Towards the east it can be seen where the expansive lava fields from Grábrók’s eruption blocked the flow of the Norðurá River, altering its course and significantly shaping the local landscape. Further down the river, the Glanni waterfall and Paradísarlaut (Paradise Hollow) are nestled within the lava field and can be easily accessed with a short walk from the Glanni car park.

The name Grábrók means "Gray Trousers" and is likely derived from the gray moss that covers the crater and lava, creating an appealing contrast with the red scoria and dark lava. Birch shrubs also grow in the lava, making this location an excellent example for studying plant succession on barren land. Lichens, algae, and mosses establish first, creating a substrate for vascular plants and birch to follow. Over 3,800 years, this delicate and vulnerable vegetation has developed, so please stay on the trails to protect it.

4. Gerðurberg: The Wall of Basalt Columns That Rocks

Location: Gerðuberg is located in Hnappadalur Valley on the South side of the Snæfellsnes Peninsula, and accessible from Route 54 via short gravel road.

Gerðuberg is an impressive geosite renowned for its striking basalt columns that line the cliffs like an immense wall. This formation is an excellent example of columnar jointing, a geological phenomenon that occurs when basaltic lava cools and contracts, fracturing into polygonal columns. The cliffs of Gerðuberg were formed around 135,000 years ago during the last interglacial period known as the Eemian. This period lasted for about 10,000 to 15,000 years before the onset of the last glacial period.

The columns at Gerðuberg are a result of significant volcanic activity from a volcano that was active in the western part of Hnappadalur. The basaltic lava from this eruption cooled and contracted, forming the hexagonal columns visible today. These columns reach heights of up to 14 meters and widths of up to 1.5 meters, creating a unique and visually captivating landscape. You can read more about how columnar basalt forms in the discussion about Stuðlagil in this article on geological sites in East Iceland.

During the last glacial period, glaciers reshaped these formations, giving them their current appearance. The process of glacial erosion exposed the columnar basalt, making Gerðuberg a prominent geological feature on the peninsula.

Hnappadalur Valley lies along an ancient rift zone that was active during the formation of the Snæfellsnes Peninsula, Westfjords, and Borgarfjörður areas around 6-14 million years ago. Around 6-7 millions ago the rift zone jumped to the current location on the Reykjanes Peninsula. The mountains surrounding Hnappadalur exhibit tilted basalt strata, a characteristic feature of successive lava flows during the Pleistocene period before the last Ice Age. Over time, tectonic forces caused these layers to tilt, creating the distinct, angled appearance of the strata.

One of the most prominent features in Hnappadalur Valley is the Eldborg Crater. Eldborg, meaning "Fire Castle," is a perfectly formed spatter cone that rises dramatically from the surrounding lava field. It was formed around 5,000 to 8,000 years ago. The valley is also dotted with numerous scoria cones and extensive lava fields. Eldborg and these scoria cones were formed during the 11th century, in the most recent volcanic event on the Snæfellsnes Peninsula.

The picturesque Þúfubjarg and Lóndrangar cliffs are remnants of ancient craters eroded by the sea.

5. Þúfubjarg & Lóndrangar: Crater's Insides Revealed by the Sea Waves

Location: The parking for Þúfubjarg-Lóndrangar parking off Útnesvegur (Road No. 574) on the south side of the Snæfellsnes Peninsula.

Þúfubjarg and Lóndrangar are two fascinating geological phenomena near the southernmost point on the coast of Snæfellsjökull volcano, connected by a 1 km long hiking trail that runs along the coast. The trail continues from Lóndrangar to the National Park Visitor Center at Malarrif. Þúfubjarg often hosts abundant birdlife, including fulmars, kittiwakes, razorbills and guillemots, and there are fox dens in the area, offering a good chance to spot an Arctic fox at this site.

Þúfubjarg is a prominent cliff composed of layered basaltic tuff. Formed during violent volcanic eruptions, the tuff was deposited in a submerged crater, later eroded by the relentless action of the sea. This erosion exposed the inner layers of the volcanic cone, creating the dramatic cliff seen today. Þúfubjarg is also home to a large population of seabirds, making it an excellent site for both geological and ecological observations. The cliff, with its complex geological history, illustrates the interplay between volcanic activity and marine erosion in shaping Iceland's coastal features. According to Icelandic folklore, Þúfubjarg is linked to the tale of Kolbeinn Grímsson, a poet who engaged in a battle of wits with the devil at the cliff's edge. This duel, representing a contest of intellect and resilience, concluded with the devil's defeat, adding an additional layer of myth to this geological marvel.

Lóndrangar are two prominent volcanic plugs rising sharply from the sea, each narrating a unique tale of volcanic activity. These geological formations are remnants of a larger volcanic crater, exposed through erosion. The taller pinnacle, reaching about 75 meters, is mainly composed of basaltic lava, while the shorter one, at 61 meters, consists of both basalt and basaltic tuff. These pinnacles are remnants of ancient volcanic plugs, where magma solidified within a vent and was later exposed by the erosion of the surrounding softer material. The formation of these volcanic necks can be attributed to violent steam explosions when magma interacted with water during the Ice Age or beneath a thin glacier near the coast.

Main source and recommended read for the Snæfellsjökull area: Snæfellsjökull - Art, Science and History of an Icelandic Volcano by Haraldur Sigurdsson volcanologist, published 2017.