From Glacial Valleys to Volcanic Vistas: North Iceland's Geosites

North Iceland is a region of stark contrasts and extreme forces that offers a compelling glimpse into Iceland's dynamic Earth processes. This region, typically divided into the northwest and northeast, presents two distinctly different geological narratives that encapsulate Iceland's natural beauty.

In the northwest, the landscape is marked by remnants of ancient glaciers. The bedrock, 2,6-11 million years old, is sculpted into deep glacial valleys, expansive bays, and fjords, separated by rugged highlands. This area tells stories of the ice that once dominated, carving and shaping the land into the breathtaking scenes we see today.

Transitioning to the northeast, the scenery dramatically shifts to a volcanic tableau, signaling our entry back into Iceland's active volcanic belt and the plate boundary of the North American- and Eurasian tectonic plates. This region is defined by its raw volcanic landscapes, which include the dramatic gorges of Jökulsá á Fjöllum and the volcanic wonders around Lake Mývatn.

While our focus may be mainly on the vibrant formations of the northeast, one must not overlook the northwest's unique geological sites. And that is where we start at an unmissable stop for any geology enthusiast touring Iceland.

How many hills are in this picture? The Vatnsdalshólar hills are famously uncountable, partly because it's tricky to tell where one hill ends and another begins!

1. The 'uncountable' Vatnsdalshólar hills

Location: Vatnsdalshólar is in the picturesque Vatnsdalur Valley in Northwest Iceland, just off Ring Road No. 1. To reach the main viewpoint, follow Vatnsdalsvegur Road 722.

Vatnsdalshólar Hill stands out as one of the region's most intriguing geological sites. As one of Iceland's "uncountable" natural wonders (alongside the islands of Breiðafjörður and the lakes in Arnarvatnsheiði), Vatnsdalshólar boasts an innumerable number of hills. The sheer number and density of these hills are unique, making it a distinctive geosite.

Believed to be the remnants of a massive landslide around 10,000 years ago, these hills vary significantly in size and shape, creating an almost otherworldly terrain. This site gives a glimpse into the powerful geological forces that have shaped Iceland.

The hills of Vatnsdalshólar are believed to be the remnants of a massive landslide that occurred around 10,000 years ago. The hills vary greatly in size, with some being mere mounds and others towering up to 30 meters high, creating an almost otherworldly landscape.

The geological formation of Vatnsdalshólar is tied to the region's glacial history. As the Ice Age glaciers retreated, they left behind unstable landmasses on hillsides. The Vatnsdalur valley is a glacial trough carved out by the massive glaciers that once covered the area. The combination of volcanic activity, glacial movements, and the eventual landslide has created today's unique topography.

The hills are primarily composed of basalt but also rhyolite, the same material found in the mountain above. Over time, erosion and vegetation have further shaped the landscape, adding to its mystique.

Vatnsdalshólar is not only a geological marvel but also the historical site of the last executions in Iceland at Þrístapar, where Agnes Magnúsdóttir and Friðrik Sigurðsson were executed in 1830, adding a somber historical layer to the area's rich geological significance.

The Lake Mývatn area is packed with geological marvels, including the striking lava pillars of Dimmuborgir that extend into the lake in some areas.

Lake Mývatn's Geosites: Three In One

The Mývatn region in North Iceland is a geological wonderland, and the region's volcanic terrain so resembles the lunar surface that it served as a training ground for Apollo 11 astronauts, including Neil Armstrong, in preparation for the first moon landing in 1969. It's impossible to choose just one geological highlight in the area and instead, we offer three must-see geosites: Dimmuborgir, Skútustaðagígar, and Hverfjall. Each site has unique features, and together, they tell the captivating geological history of Lake Mývatn and the Laxá River. Here, you can find a map with highlights of the Lake Mývatn area.

Lake Mývatn, situated in a rift zone associated with the Krafla volcanic system, was formed in a subsidence area between faults (a rift valley). Over 2,000 years ago, a significant volcanic event dramatically reshaped this landscape. During the Þrengslaborgir and Lúdentsborgir eruption series, vast amounts of lava flowed from a 12 km-long fissure, creating the younger Laxárhraun lava field. This extensive lava field, covering about 220 km², is the largest in the Mývatn area from the Holocene period (past 10-12 thousand years). The lava flowed approximately 50 kilometers down the Laxá River valley, reaching the sea at Skjálfandi Bay, forming the bed of the current Lake Mývatn and regulating water flow in the region.

Dimmuborgir (meaning dark fortresses or dark castles) is a labyrinth of lava formations that emerged from this younger Laxárhraun lava flow. Formed by thin lava crusts that created a nearly circular blister, Dimmuborgir features dramatic troll-like rock pillars, caves, and arches. The formations result from a lava pool overflowing, creating thin lava splashes and building up the distinctive structures we see today. Dimmuborgir is a type of lava blister built from thin lava crusts. This nearly circular blister, about 2 km in diameter, is highest in the center, approximately 20 meters above the surroundings, with a gentle slope outward. In the blister's center was a lava pond, and thin lava splashes flowed to the sides, gradually building up the blister. Eventually, the blockage of the lava lake burst, releasing the trapped molten lava beneath. This outflow caused the surface layer to collapse in certain areas, yet some of the earlier-formed vertical structures remained standing as pillars. The area contains significant amounts of scoria and spatter, indicating its relation to pseudocraters. Dimmuborgir is located on the east bank of Lake Mývatn and accessible via Route 848. See the location on a map.

The Skútustaðagígar pseudocraters add another layer to Mývatn's geological narrative. These craters formed in the same eruption as Dimmuborgir, when the lava flowed over wetlands, causing steam explosions that created crater-like formations. Skútustaðagígar are exceptionally beautiful examples of this rare phenomenon and offer a glimpse into the dynamic interactions between lava and water. Situated on the southern shore of Lake Mývatn, they are easily reached by following Route 848. An ideal viewing spot is at the Lake Mývatn Visitor Center.

Mt. Hverfjall has a towering presence and well-preserved structure, making it a significant feature in the Mývatn landscape. Its steep slopes and crater rim provide stunning views of the surrounding area, illustrating the magnitude of the volcanic activity that formed it. Hverfjall was likely formed about 2,800 years ago in a lake that was the precursor of Mývatn during an eruption along a 25 km-long fissure from Hverfjall in the south to Éthólar in the north, known as the Hverfjall fires. Hverfjall is a tephra cone, similar to Surtsey Island, formed by steam explosions when basaltic magma came into contact with water. At the time of this eruption, Mývatn probably extended to the current location of Hverfjall. When such eruptions occur, the magma shatters due to steam explosions and becomes ash that accumulates around the vent. Lava from this eruption can still be seen on the eastern shore of Ytriflói. Hverfjall is visible from many parts of the Mývatn region. The shortest route to hike Hverfjall starts from the parking area at the mountain's base. See on a map here. The hike is about a 2-3 km round trip around the crater rim, with an elevation gain of approximately 120 meters.

It must be mentioned that on sunny summer days, visitors to the Mývatn area should not forget their insect nets, as Mývatn lives up to its name with many midges. In the summer, you can often see impressive columns of midges rising from the lake, which is quite a sight. Mývatn is the third largest lake in Iceland, covering an area of 37 km², and its ecosystem is unique. Silica algae form the base of the food chain, feeding the midge larvae, which nourish the fish and birds. Mývatn is a geological marvel and an exceptional bird-watching site; for example, the rare gyrfalcon is a fairly common sight, and Mývatn hosts more duck species in one location than anywhere else.

Are we still on Earth? The colorful landscape with boiling mud pots, hissing steam vents, and a strong sulfur smell give visitors an otherworldly feeling at Hverarönd sulfatarra area.

3. Hverarönd sulfatarra area: Unearthly Landscapes

Location: Hverarönd (Hverir) is east of Lake Mývatn, accessible via Ring Road no. 1.

! Visitors are urged to stay on marked trails due to the dangerously deceptive terrain with unstable ground and hot surfaces.

Hverarönd (also called Námaskarð or Hverir), located near Mt. Námafjall in North Iceland, is a geothermal field renowned for its intense geothermal activity and unearthly landscape. Magma intrusions from the Krafla volcanic system power this high-temperature area. It lies within a dense fracture zone extending from Öxarfjörður through the Krafla volcano to the south of Hverfjall. They are known as Hverarönd, the region east of Námafjall, which is characterized by boiling mud pots and fumaroles but lacks hot water springs. Most of the fumaroles are essentially old boreholes now covered with stones. They emit powerful steam and noise, adding a dramatic element to the landscape.

The terrain in Námaskarð is barren and devoid of vegetation, with the soil rendered acidic and infertile due to geothermal emissions, which deposit sulfur across the landscape. Historically, Námaskarð was a significant site for sulfur mining used in gunpowder production during the Middle Ages. The wealth from sulfur mines, owned by the Danish crown from 1563, was actively used until the mid-19th century. A factory was even built in Bjarnarflag in 1939 to process the sulfur, and it has been operating for several years.

Formation of Mud Pots and Color Variations:

The boiling mud pots at Hverarönd are created through the interaction of geothermal heat and surface water. As groundwater seeps into the Earth's crust, it comes into contact with hot rocks heated by the underlying magma. This interaction causes the water to boil and rise to the surface, bringing dissolved minerals and gases.

Mud pots are formed when hot, acidic water reaches the surface and reacts with the surrounding soil and rocks, turning them into clay. The constant boiling and churning of this mixture creates the bubbling mud pots.

The different colors in the mud pots and surrounding terrain are due to the various minerals brought to the surface by the geothermal activity. Common colors include:

• White and Gray: These colors are typically due to silica and clay.
• Yellow and Orange: These hues are caused by sulfur and its compounds, which are abundant in geothermal areas.
• Red and Brown: Iron oxides can give the mud and soil these shades, indicating the oxidation of iron (rusting).
• Green: The presence of minerals like chlorite or even algae can produce greenish tints.

Krafla volcano is one of the most intriguing geosites in Iceland, offering many easily accessible features of an active volcano, including a massive explosion crater, mud pots, steam vents, and fresh craters and lava fields from the Krafla fires of 1975-1984.

4. Krafla Central Volcano: Inside the Inferno

Location and hiking: The Krafla area is east of Lake Mývatn, accessible via Route 863. First, you pass the geothermal power plant Krafla and reach the parking for Leirhnjúkur. There is an easy trail to the geothermal area at Leirhnjúkur, passing through hot springs and steaming lava to craters formed in the Krafla fires (1975-1984), with a hiking path extending to the beautifully formed Hófur crater, dating back to the Mývatn fires (1725-1729), taking 1-3 hours depending on how far you go. The parking for the Krafla Viti explosion crater view is just 1 km further, right on the rim of the crater.

Krafla is one of the most studied volcanic areas in Iceland, located near Lake Mývatn in the country's northeastern region. This central volcano is known for its striking caldera, about 10 kilometers in diameter, and a series of eruptions that have shaped its current landscape. What sets this central volcano apart is its relatively flat slopes, allowing visitors to drive into the caldera and explore a variety of features, including craters at Leirhnjúkur volcano, lava fields, mud pots, and the impressive explosion crater, Víti. Visiting Krafla is a unique experience where you can genuinely feel the roaring power of the volcano beneath your feet.

Krafla is a classic example of a central volcano, characterized primarily by its caldera, filled predominantly with younger geological strata or layers. Directly beneath Leirhnjúkur volcano, a magma chamber sits at 2-4 kilometers deep. Krafla belongs to the Northern Volcanic Zone (NVZ) of Iceland. Geologists have divided the rift zone running through Iceland into several belts based on their distinct characteristics. The NVZ contains several volcanic systems, with Askja being the most famous, alongside Krafla. The belt connected north of the Northern Volcanic Zone is the Tjörnes Fracture Zone, where the tectonic plates slide past each other, causing significant earthquakes (up to M7) similar to those in the South Iceland Seismic Zone (SISZ).

The Krafla Fires, a notable series of volcanic eruptions and magma intrusions, spanned from December 20, 1975, to September 18, 1984, marking a period of significant geological activity near Krafla. This tumultuous era began with an eruption at Leirhnjúkur, coinciding with the construction of the Krafla Power Station. As magma accumulated in the underlying chamber, increasing pressure forced it into newly formed fissures, resulting in 24 distinct intrusion events and nine surface lava flows. This series of events, collectively known as the Krafla Fires, profoundly altered the landscape, causing noticeable land uplift, subsidence, and seismic activity within the caldera and its vicinity. The eruptions produced extensive lava fields, known as Leirhnjúkshraun, covering 33 km². This intense volcanic activity at Krafla parallels recent events on the Reykjanes Peninsula, where similar geological processes have led to spectacular eruptions and underscored the dynamic nature of Iceland's volcanic regions.

Víti, meaning "hell" in Icelandic, is an impressive explosion crater in the Krafla caldera. Formed during the massive 1724 Krafla eruptions, which initiated the Mývatn Fires that lasted until 1729, Víti's creation is a result of a volcanic explosion that left behind a circular crater approximately 300 meters in diameter. Today, Víti enchants visitors with its serene aquamarine lake, taking its color from algae that thrive in the water.

On the way to Krafla volcano, you will notice the prominent pipes and boreholes connected to the Krafla Power Station. This significant geothermal power plant harnesses the region's abundant geothermal energy. Commissioned in 1977, the plant has a production capacity of approximately 60 MW and utilizes steam from deep geothermal wells to generate electricity. Krafla is part of the Krafla volcanic system, a site of intense geothermal activity and research.

In 2009, the Krafla Power Station became a focal point for the Iceland Deep Drilling Project (IDDP), a pioneering initiative exploring supercritical geothermal resources. During drilling, the IDDP team unexpectedly struck magma at a depth of 2.1 kilometers. This discovery provided a unique opportunity to study the interaction between geothermal wells and magma and demonstrated the potential for significantly enhanced geothermal energy production. The Krafla Power Station remains an essential site for energy production and groundbreaking geothermal research.

5. Dettifoss: The Diamond of the North

Location: Dettifoss is accessible from both the west and east sides. Route 862 (Vesturdalur Road) leads to the west side and is recommended for most visitors, with a 1 km hike to the main viewpoint. The east side viewpoint is accessible only during the summer via gravel Route 864 (Hólsfjallavegur).

Dettifoss, located in Northeast Iceland, is one of Europe's most powerful waterfalls. The waterfall is fed by the glacial river Jökulsá á Fjöllum, Iceland's second largest river originating from Vatnajökull Glacier. Dettifoss is a spectacular display of raw, untamed nature and a highlight of the Northern Area of Vatnajökull National Park.

The immense power and grandeur of Dettifoss stem from the river's high flow rate and a dramatic 44-meter drop into the rugged Jökulsárgljúfur Canyon. This force creates a mist plume visible from kilometers away, and the thunderous roar of the waterfall's immense power can be heard from afar. The surrounding area, marked by basalt columns and volcanic ash, adds to the scenic beauty and provides insight into the ongoing volcanic processes in Iceland's volcanic zone.

The Jökulsárgljúfur Canyon was formed primarily by catastrophic glacial flooding from volcanic eruptions beneath a glacier and features dramatic, steep walls. Extending about 25 kilometers downstream, it includes the remarkable horseshoe-shaped Ásbyrgi. According to legend, Ásbyrgi was formed by Sleipnir, Odin's eight-legged horse, though geologists attribute its creation to massive glacial floods.

Dettifoss is part of a scenic route known as the Diamond Circle, which refers to the famous Golden Circle in South Iceland.

If visibility is good while traveling through the Mývatnsöræfi highland area towards Dettifoss, don't miss the opportunity to notice Herðubreið to the south. Herðubreið, one of Iceland's highest mountains, is renowned for its striking shape and is universally known as the queen of Icelandic mountains. Beloved by Icelanders, Herðubreið is often cited as a favorite mountain by many. This iconic peak is a so-called table mountain formed by volcanic eruptions beneath a glacier.

Standing at 1,686 meters, Herðubreið is the 11th highest peak in Iceland and is universally referred to as the "Queen of Icelandic Mountains" due to its striking form. It is a favorite among Icelanders and was voted Iceland's national mountain in 2002. Herðubreið is a table mountain formed in a volcanic eruption beneath a glacier, with lava layers on top, indicating that the eruption broke through the ice.