Which term refers to translational movement involving many units?

The term that refers to translational movement involving many units is known as "block slide." In geological terms, a block slide occurs when a large mass of material moves down a slope along a planar surface, often over a significant area. This type of translational movement is characterized by the relatively coherent movement of multiple units of rock or soil, which may detach from the slope due to factors like gravity, saturation from rainfall, or undercutting.

Understanding "block slide" is crucial in geology as it helps identify and assess hazards in areas where such movements can occur, particularly in mountainous regions or sites with steep gradients. By recognizing the mechanisms and characteristics of block slides, geologists can better evaluate slope stability and implement appropriate risk management strategies.

The other terms do not accurately describe the specific process of translational movement involving many units. A "slump" typically involves rotational movement and local failures, while "translation" alone is a broader term and not specifically defined in geological contexts. "Slidie" is not a recognized geological term.