Basaltiska

Basaltiska, or basaltic, refers to rocks and magmas that are rich in magnesium and iron and relatively low in silica. This mafic character gives basaltic rocks a dark color and typically fine-grained texture. The most common basaltic rock is basalt, which is predominantly composed of plagioclase feldspar and pyroxene, with olivine present in more primitive varieties. Silica content generally falls in the about 45 to 52 percent range. Basaltic rocks can be aphanitic (fine-grained) or porphyritic, containing small crystals embedded in a finer groundmass.

Formation and occurrence: Basaltic magmas originate at tectonic settings where mantle material melts to produce low-viscosity lava, such as mid-ocean ridges and volcanic hotspots, and they also occur in continental flood basalts. When erupted on the surface, basaltic lava forms flows that can blanket large areas, sometimes creating lava plateaus. Underwater eruptions produce pillow lavas. The world’s oceanic crust is largely basaltic, whereas continents host scattered basalt flows and larger basalt provinces in flood-basalt episodes.

Classification and variation: Basaltic rocks are commonly grouped into tholeiitic and alkaline series, reflecting differences in trace-element chemistry and alkali content. They may host a range of accessory minerals, including magnetite and titanium-bearing oxides, and can display various textures from glassy to finely crystalline.

Uses and significance: Basalt is widely used as a construction material and aggregate, and specialized products such as basalt fiber have grown in industrial use. Columnar jointing is a notable geometric feature associated with some thick basaltic lava flows.