ALKALI BASALTS Meaning and
Definition
-
Alkali basalts are a type of volcanic rock that belong to the basaltic family. Basalt is a dark, fine-grained igneous rock that is rich in iron and magnesium, commonly formed from the rapid cooling of lava that has erupted from a volcano. Alkali basalts specifically refer to basaltic rocks that are characterized by a relatively higher abundance of alkali elements, such as potassium and sodium, compared to other types of basalts.
These rocks are primarily composed of minerals such as plagioclase feldspar, pyroxenes, and olivine. The presence of alkali minerals, such as alkali feldspar, differentiate alkali basalts from other basalts. The alkali minerals give these rocks distinct chemical and mineralogical characteristics.
Alkali basalts are typically dark gray to black in color, with a fine-grained texture, similar to other basalts. They often exhibit a porphyritic texture, meaning that larger crystals, or phenocrysts, are embedded in a fine-grained matrix.
These rocks are commonly found in volcanic regions and are associated with relatively low-viscosity magma, which allows the lava to flow more easily during eruptions. Alkali basalts are generally associated with higher-temperature volcanic activity and can sometimes be found in continental rift zones, oceanic islands, or in volcanic arcs.
As with other basalts, alkali basalts have various uses in construction, including as aggregate material for roads, railways, and concrete. They can also be used as a decorative stone and for the production of crushed stone products. The study of alkali basalts is important for understanding the geological history and volcanic activity of different regions.
Etymology of ALKALI BASALTS
The term "alkali basalts" combines two different words, each with their own etymology:
1. Alkali: The word "alkali" originates from the Arabic word "al-qalī" (القلي), which means "ashes of the saltwort plant". In Arabic, "al" refers to "the", and "qalī" identifies the saltwort plant. Over time, the term "alkali" was adopted into various European languages, including English.
2. Basalt: The term "basalt" comes from Late Latin "basaltes", which originally derived from Ancient Greek "básalts" (βάσαλτος). The Ancient Greek term referred to a black, fine-grained rock believed to be used as a touchstone.
