What is basalt?
Basalt is one of the most important and common extrusive volcanic rocks. Based on how rapid cooling of lava at the surface of earth is, it usually is in grey to black colors. Basalt is an igneous rock and it is mainly composed out of plagioclase and pyroxene minerals, similarly to gabbro. the difference between them is that basalt has a fine-grained texture while gabbro is a coarse-grained rock. Basalt can form as an extrusive rock from lava flow or it can form in small intrusive bodies like a thin sill. Most of basalts specimens are compact, fine-grained, and glassy. the holes left by gas bubbles in its texture, can give it a coarsely porous look and many people buy basalt to decorate their countertops or create beautiful floors.
As a Bedrock
One of the important facts about basalt is that, it is the most abundant bedrock on earth which means that it covers the most of the surface of earth. For instance, ocean basins most areas are underlain by basalt. However, it is not a common rock on surfaces of the continents. An interesting fact about basalt is that, it also covers the Moon and much of the Moon’s surface is made out of flood basalts or basaltic lava flows. These areas on the Moon are called “lunar maria.”
Formation
Earth’s basalt can mostly be found on three environments, In order of oceanic divergent boundaries, oceanic hotspots, and mantle plumes or hotspots under the continents.
Most of the basalt on Earth is built on the mid-ocean ridge system at divergent plate boundaries. in this process, convection currents will deliver hot rocks out of deep in the mantle. This hot rock melts and pulls apart at the divergent boundary then molten rocks erupt in to the sea floor. These eruptions often produce basalt rocks with shapes like pillow. The repeated fissure eruptions happen, mostly in the active mid-ocean ridges. by being under the deep waters, most of these activities are unnoticed and anything made out of this process like ash, steam or gas is absorbed by the water and cannot reach the sea level. the only notice able sign for humans is earthquakes. except for the Iceland because it is a location where a mid-ocean ridge is sea level and visible to the naked eye; so people can see the volcanic activities directly.
Second place where great amounts of basalt are produced is on the oceanic hotspots. In These locations, a small plume of hot rock rises up out of the mantle from a hotspot on Earth’s core. This process starts with a great eruption on the ocean floor. If the process of eruption happens repeatedly, these hotspots can make the volcanic cone larger enough to build an island. For instance, the Hawaiian Islands have been built from this process above one of the oceanic hotspots.
The last basalt-forming environment is in a continental environment. On this process a mantle hotspot surrenders enormous amounts of basaltic lava out of the continental crust on to Earth’s surface, Vents or fissures can form these eruptions. These eruptions can repeatedly happen for millions of years and produce layers of basalt stacked in a vertical formation.
Uses
Now a days, basalt has wide range of uses. The crushed form of it can be used as an aggregate in construction projects, road beddings, concrete aggregate, asphalt pavement aggregate, railroad ballast, filter stone and may other purposes. It also can be cut into dimension stones and polished for uses such as floor tiles, pavers, building facades, monuments, and even art.
As mentioned before, Basalt is mainly used as a structural material in forms of bricks, tiles, foundations and sculptures. Also, for thermal purposes within stonewalls, rail tracks and it can serve well as an insulator and around the fireplaces for interior design purposes. also to keep people out of harm way from toxic effects of basalt, it can be used as a replacement for asbestos.
Basalt is rigid and dense which is why, that it has a lot of purposes in construction. In construction, large slabs of Basalt can be used as tiles and bricks. Basalt fiber is a material made out of extremely fine basalt fibers, it is similar to fiberglass except with better mechanical properties than fiberglass. By being significantly cheaper than carbon fiber, it is used to make blades for wind turbines.
Basalt has a rich history in architecture, both in interior and exterior design and for many purposes. For instance, it was used for urban design as tiles to pave the streets mostly in locations near the volcanoes. Another interesting use of basalt was as stadium seating. throughout the Roman Empire, Basalt had its most use for construction and architecture.
Weathering
Basalt is rich with iron and magnesium and it has a main composition of olivine, pyroxene, and plagioclase. In Comparison to other rocks on earth, basalts can weather rapidly. Due to the fact that the iron-rich typed of minerals oxidize fast in water and air. Because of the rust, it leaves a brownish to red color stain on the rock. Chemical weathering can quickly release water-soluble cations such as calcium, sodium and magnesium, which gives the basaltic areas a great buffer capacity upon the acidification. We should note that these eruptions of basalt can release of large amount of quantities of CO2 into the atmosphere from volcanic gases.
Basalt aggregates
Based on the Studies researching the effect of addition of basalt components on individual properties of sand-lime products, the following conclusions were made:
- the addition of basalt aggregate and crushed basalts to some sand-lime products can increase the compressive strength of them.
- With the increase in the proportion of basalt aggregate and crushed basalt, the bulk density of sand-lime products will increase to. Because of low mass content, basalt fibers do not significantly affect volumetric density changes.
- The number of micropores changes, which means change in the physical and mechanical properties of the material, as well as microstructures.
