Question

the lack of large talus accumulations at the base of many canyons and erosional remnants may be explained by _. long periods of erosion removal of talus by stream erosion young age of the rock slopes

Explanation:

Talus accumulations are often removed by stream erosion over time. Long - term stream action can carry away the debris that would otherwise accumulate as talus at the base of slopes. Young age of rock slopes would not prevent talus accumulation. Long periods of erosion alone do not necessarily mean lack of talus as erosion can also contribute to talus formation in some cases.

Answer:

removal of talus by stream erosion