Final answer:
A cohesive lahar is a mudflow composed of volcanic materials mixed with water that flows rapidly downhill, and can contain large rocks and boulders due to the binding clay and mud. It is associated with active volcanic areas such as those in Hawaii, where the presence of lava and volcanic debris combines with water to potentially form lahars.
Step-by-step explanation:
A cohesive lahar is a type of volcanic mudflow that includes a mix of volcanic material, such as pyroclastic debris, ash, and particularly lava with significant water content that gives it a concrete-like fluidity. The term lahar is specifically applied to mudflows related to volcanic activity, and the adjective cohesive refers to lahar that has a considerable amount of clay and mud, which act as a binding agent to hold the larger volcanic rocks and boulders together. Lahars are a dangerous volcanic event that can flow rapidly downhill due to gravity, destroying almost anything in their path.
For instance, the vesicles and phenocrysts found in the basalt sample from the Kapoho Eruption, as described by James St. John, are characteristics of the materials that might form a part of the solid components of a cohesive lahar. Additionally, an agglomerate is analogous in size to the particles typically found in lahar, but cohesive lahars are particularly fluid, allowing them to flow and transport these large fragments over great distances.
As we can learn from the geothermal activity depicted in the lava flows near Mauna Ulu Lava Field and those seeping east of Pu'u 'O'o crater, Hawaii's volcanic regions are prime origin points for lahars due to the presence of flowing lava, volcanic debris, and interaction with water sources.