Answer:
Tectonic activities
Explanation: Tectonic activities which affect position of rock can wear down the new rock formed by the magma. Tectonic activities can be a new volcanic eruption or earthquake. Pyroclastic flow of volcanic eruption can destroy anything in its path. As hot lava (temperature more than 2000 degree centigrade) oozes down steep slope it breaks apart into hot rocks and gases (mainly sulfur dioxide) called pyroclastic flow.
