Reykjanes Peninsula Day Trip
This trip starts and ends in Reykjavík; expected duration is 10 hours. You will learn about the geology of Reykjanes peninsula. We will make several stops along the way, with the 4 highlights listed below.
Reykjanes Peninsula Geology
When landing in Iceland, many people compare it to landing on the moon. Today, you might certainly feel like you are on another planet going through the various lava fields, some covered in moss, while others are more rough on the edges, as we drive through the unique landscape. We will explore the Reykjanes peninsula, which is a UNESCO Global Geopark, and also one of very few places in the world where the Mid-Atlantic Ridge is visible and rises out of the sea. Where the ridge continues underwater, southwest of the land, it is called Reykjaneshryggur, or the ridge of Reykjanes.
The land in the peninsula is considered young in geological terms, and a highly volcanic part of Iceland. An active eruption belt lies under the peninsula, with four systems and fissure swarms lined from Southwest to Northeast. These contain open fissures, normal faults, high temperature geothermal fields and volcanic fissures lined with monogenetic craters. The geology is fascinating! The area contains late Quaternary volcanic palagonite tuff and pillow lava in formations of mountains from the last glacial periods. From the Holocene period, volcanic structures from interglacial periods like basaltic lava flows.
The Reykjanes peninsula is about 1,700 km2, with a range of mountains in the middle, commonly called Reykjanesfjallgarður, almost continuous from south of Mt. Esja and Mt. Hengill in the east, to the end in Valahnúkur west of Reykjanes. Glacial and submarine volcanic structures can be seen in this mountain range. Otherwise, the landscape is flat and has coastline all around except in the east. The capital of Iceland, Reykjavík, along with the largest suburb areas in the country form together the Capital area, which lies on the east edge of the peninsula, and the international airport in Reykjanesbær, usually called Keflavík, is about 40 km from the capital area.
In one of our stops you will have a chance to see the tectonic plates—which I will do my best to explain in layman’s terms—for you to understand how Iceland, and Reykjanes peninsula, were formed.
The Earth’s inner structure consists of several layers: the crust, the solid upper mantle, the lower mantle, the liquid outer core and solid inner core. A layer about 100 km thick, made up of a combination of the crust and the upper mantle, form the lithosphere. This is broken up into many plates, which are called tectonic plates. The lithosphere consists of both continental crust and oceanic crust, which surfaces in the ocean basins. The tectonic plate can be seen as a massive slab of solid rock that floats separately from the other tectonic plates. The continents are embedded in the plates, and drift along as the plates move. But how can they float and move?
Imagine an iceberg floating. Not so much unlike that, the reason the tectonic plates can float is because the oceanic crust consists of higher density basaltic rocks, which are heavy, while the continental crust is predominantly made up of granitic rocks, which are much lighter.
Here in Iceland, one can see the result of the divergent, spreading boundary between two plates, the Eurasian tectonic plate and the North American tectonic plate, as the two plates moved apart and excessive eruptions of lava formed volcanoes and filled rift valleys. Between 90 and 150 million years ago, the divergence of the ridge started and still continues accompanied by earthquakes, reactivation of old volcanoes, and creation of new ones. It moves on average about 2 cm per year while the tectonic plates move slowly towards the northwest.
On land in Reykjanes, the southwestern outpost of Iceland, the rift valley could be called a ‘no mans zone or land’ where it covers a shallow 10 km wide area.