Kirkjugolf, a geological feature in Iceland, presents a unique landscape. Its distinctive appearance, resembling a meticulously laid church floor, has led to a common misconception about its rock type. Known locally as “Kirkjugólf” or “church floor,” this natural monument showcases a pavement of polygonal stones that appear almost man-made. The site is a protected natural monument in South Iceland, characterized by low columnar basalt rock where the tips of the columns face up from the ground.
Sedimentary vs. Igneous Rocks
Sedimentary rocks develop from the accumulation and compaction of sediments, which are fragments of pre-existing rocks, minerals, or organic matter. These materials are transported by agents like wind, water, or ice, and then deposited, often in layers, before undergoing compaction and cementation into solid rock. Sedimentary rocks frequently contain fossils and exhibit distinct layering.
In contrast, igneous rocks originate from the cooling and solidification of molten rock. This molten rock, called magma when beneath the Earth’s surface and lava when it erupts, hardens as it loses heat. Igneous rocks are classified based on whether they form intrusively (below the surface) or extrusively (on the surface), with their crystal size depending on the cooling rate.
Kirkjugolf’s True Identity
Despite its name and tiled appearance, Kirkjugolf is not a sedimentary rock formation. It is an igneous rock, composed of basalt columns. The hexagonal shapes are a result of a natural geological process, not sedimentation or human construction. The illusion of a man-made floor stems from the remarkably uniform and precise arrangement of these columnar basalt structures.
The site covers approximately 80 square meters and consists of hexagonal basalt stone slabs. While some parts are covered by moss and grass, the patterned basalt columns are clearly visible.
The Formation of Kirkjugolf
Kirkjugolf’s unique appearance is a product of columnar jointing, a geological process where molten basalt lava cools and contracts. As thick lava flows cool slowly and uniformly, they develop a network of cracks that extend downwards. These cracks typically form polygonal prisms, most often hexagonal, but also pentagonal or octagonal.
The cooling lava shrinks, causing tensile stress that is relieved by these fractures. The cracks propagate perpendicular to the cooling surfaces, resulting in the pillar-like structures observed at Kirkjugolf. This process is common in basaltic lava flows due to their tendency to form thick, homogeneous beds that cool gradually.