Why did cooley refer to some groups as "primary groups"?

the correct answer is 2.

a slump in geology means a mass movement process of slope failure. a mass of rock or unconsolidated material drops along a slip surface. in other words, rock layers move a short distance down the slope. the slump block is an intact block (2), without any landslide material.

in this image, 1 is the surface of rapture (scarp), 2 the slump block, 3 main scarp (crown), 4 base of rapture with debris flow.

slumps are caused by clear cutting on unstable soils and the sagging of earth, in coastal areas they are due to wave infiltration.

can you give a picture of the map, i'll be able to update my answer!