Glacial till groupings?

Glacial till groupings?

• A. Compact or lodgment till (dense basal till) and loose Sandy till (ablation till)
• B. Fine-grained till and coarse-grained till
• C. Welded till and broken till
• D. Wind-blown till and water-laid till

Answer: (A)

Glacial till groupings are based on how the sediment was deposited by the glacier and how that process affects density and texture. The two main types are compact or lodgment till, which is a dense basal till formed as ice presses sediment against the bed and lodges it under the glacier, giving a thick, stiff, low-porosity deposit. The other type is loose sandy till, produced during ablation when the glacier melts and debris is dropped or carried away by meltwater, resulting in a looser, often sandier, higher-porosity deposit with better drainage. This distinction—dense basal lodgment till versus looser ablation till—best captures the typical grouping used in soil science for glacial deposits. The other descriptions (by simply grain size, or by terms like welded/broken, or wind- or water-laid) don’t reflect the standard glacial-till classifications, which hinge on formation process during different glacier phases.

Glacial till groupings are based on how the sediment was deposited by the glacier and how that process affects density and texture. The two main types are compact or lodgment till, which is a dense basal till formed as ice presses sediment against the bed and lodges it under the glacier, giving a thick, stiff, low-porosity deposit. The other type is loose sandy till, produced during ablation when the glacier melts and debris is dropped or carried away by meltwater, resulting in a looser, often sandier, higher-porosity deposit with better drainage. This distinction—dense basal lodgment till versus looser ablation till—best captures the typical grouping used in soil science for glacial deposits. The other descriptions (by simply grain size, or by terms like welded/broken, or wind- or water-laid) don’t reflect the standard glacial-till classifications, which hinge on formation process during different glacier phases.