Technical Report No. 497. Landslide is a nontechnical term which implies a specific type of mass movement. Mass wasting is the technical term which can be applied to any kind of mass movement. Earth scientists prefer the term mass wasting. Lahar is the Indonesian term for a mud or debrisflow formed by addition of excess water to volcanic sediment, usually ash.
Rockslides occur along a preexisting tilted fracture surface or bedding surface.
Slumps occur along a newly-formed surface of rupture formed due to increase of slope gradient of amount of water within slope material. Plastic tarps are emplaced to drain off moisture before it can interact with the slope material below. Yes, tarps do decrease likelihood of mass wasting. Shear stress produced by downward pull of gravity acting on slope material. Include information about slope, consolidation, water, and ground cover.