Agglomerate is a coarse, volcanic rock composed of angular fragments of volcanic material that have been welded or cemented together. It forms from explosive volcanic eruptions and is typically found in volcanic settings, such as around vent areas. Agglomerates are important for understanding the eruptive history and dynamics of volcanoes.
Reference: Williams, H., & McBirney, A. R. (1979). Volcanology. Freeman, Cooper & Company.