Here's a breakdown of the differences:
Felsic Lava (previously called "acid lava")
* Composition: Rich in silica (SiO2), typically over 65%. Contains high amounts of potassium, sodium, and aluminum.
* Viscosity: Very thick and sticky. This is due to the high silica content, which forms complex, interlocking structures.
* Eruption style: Explosive eruptions. The high viscosity traps gases, creating pressure that builds until a violent eruption occurs.
* Examples: Rhyolite, dacite.
* Appearance: Often light-colored, can be pink, gray, or even black. Can form steep, blocky lava flows.
Mafic Lava (previously called "basic lava")
* Composition: Low in silica (SiO2), typically less than 50%. Contains high amounts of magnesium, iron, and calcium.
* Viscosity: Thin and fluid. The lower silica content allows for smoother, less complex structures.
* Eruption style: Effusive eruptions. The fluid lava flows easily and can spread out over long distances.
* Examples: Basalt, gabbro.
* Appearance: Typically dark-colored, often black or dark gray. Can form smooth, ropy lava flows.
Here's a table summarizing the key differences:
| Feature | Felsic Lava | Mafic Lava |
|---|---|---|
| Silica Content | High (over 65%) | Low (under 50%) |
| Viscosity | High | Low |
| Eruption Style | Explosive | Effusive |
| Appearance | Light-colored | Dark-colored |
Important Note: There is a middle ground between these two extremes. Lava with intermediate silica content and viscosity is classified as intermediate lava. Examples include andesite and diorite.
Understanding the differences between felsic and mafic lavas is crucial for understanding volcanic activity and its effects.
