Lapilli is a term associated with which type of geological material?

Lapilli refers to a specific type of pyroclastic material that consists of small rock fragments ejected from a volcanic eruption. These fragments are typically between 2 and 64 millimeters in diameter and are a common product during explosive volcanic events. Pyroclastic materials encompass a variety of volcanic products, including ash, pumice, and volcanic rocks, but lapilli is a distinct category within that classification due to its size range and formation process.

When a volcano erupts, the explosive force can fragment magma and surrounding rock, launching these pieces into the air, where they cool and fall back to the ground. This process leads to the accumulation of lapilli as well as other pyroclastic materials. Understanding lapilli is crucial in the study of volcanic activity and stratigraphy, particularly in archaeological contexts like Pompeii and Herculaneum, where deposits from eruptions have preserved the sites for study.

In contrast, while volcanic ash and igneous rocks relate to volcanic activity, they denote different aspects of volcanic geology. Volcanic ash refers specifically to very fine particles, while igneous rocks result from the cooling and solidification of magma, which can include lapilli but is broader in definition. Granular sand does not fit within the