A geologist is looking at deposits along a river below a large volcano. she finds large boulders mixed with sand and mud, and all of the material is comprised of volcanic rocks, particularly the mud which is volcanic ash. she quickly realizes these deposits represent an ancient ________. a geologist is looking at deposits along a river below a large volcano. she finds large boulders mixed with sand and mud, and all of the material is comprised of volcanic rocks, particularly the mud which is volcanic ash. she quickly realizes these deposits represent an ancient ________. lahar earthflow rock avalanche slump