- Refers to substances or rocks that have a high pH value (greater than 7) and are basic in nature. In the context of igneous rocks, alkaline rocks have relatively high levels of alkali metals like potassium and sodium.
- 2. A type of igneous rock that has a relatively high content of alkali metals (such as potassium and sodium) and low silica content. Alkaline rocks typically form in regions associated with volcanic activity.