These concepts would be communicated using a combination of signs or fingerspelling and the classifier system of ASL. "Landslide" for example would be signed PROPERTY L-A-N-D CL:BB-moving-together-in downward-motion-showing-movement-of-the-land-down-side-of-mountain-or-whatever-surface-land-is-moving-on
Mudslide would be communicated in a similar manner with first fingerspelling M-U-D
Rockfall would be communicated similarly but with a different classifier handshape as in ROCK/STONE CL:Claw-hand Claw-hand-showing-motion-of-rocks-falling/tumbling-from-side-of-mountain-or-whatever-surface
Sinkhole would be communicated similarly through classifiers as in PROPERTY/LAND CL:BB-showing-surface-area-where-sinkhole-occurred CL:index-finger-outlining-circle [possibly adding sign for size as in LARGE or SMALL] CL:BB-fingertips-facing-each-other-showing-land-sinking-inward-collapsing DEEP ABOUT [provide estimate of how deep the sinkhole is/was
Not really that difficult except for knowing which classifiers to use and how to use them appropriately to describe the natural phenonmenon
Hope this helps answer your question
Bill
