Ground water causes erosion when it's constantly running/landing on the same surface and each time it does this, it washes away a bit at the surface at a time. it causes deposition when it carries the eroded materials away and drops it off somewhere else.
Groundwater<span> also can </span>cause erosion<span> under the surface. As water flows through the soil, acid is formed. ... Minerals that are carried in </span>groundwater<span> can also be </span>deposited<span> in other places. This cycle of </span>erosion and deposition<span> can </span>cause <span>underground caves to form.</span>
the side of the volcanoes and other pyroclastic ejecta become saturated with water
Explanation:
A pyroclastic flows can generate the lahar when they are extreme ty hot and flows with the rocks bedrock. This debris mixes up with the snow met and ice and gets rapidly traveled upwards.
It travels rapidly down steep slopes and a larger can also be formed when a high volume of long duration of rainfall occurs after the eruption. And the volcanic landslides are mixed with water.
