GLACIAL SEDIMENTS — Name for basal, unsorted debris What do geomorphologists call the unsorted sediment deposited directly by a glacier at its base or upon melting?

Introduction / Context:
Glacial environments produce distinctive deposits. Correctly naming them is essential in interpreting past ice coverage and reconstructing paleoenvironments.

Given Data / Assumptions:

• Material is unsorted (mix of clay to boulders).
• Deposited directly by ice (not by meltwater streams).
• Location may be beneath (basal), at front, or upon melting.

Concept / Approach:
“Till” is the unsorted, unstratified sediment laid down directly by glacial ice. “Moraine” refers to landforms composed of till (e.g., terminal, lateral, ground moraines) rather than the sediment type itself. “Glacial sand” and “varve clay” are water-laid and often stratified.

Step-by-Step Solution:
Match the keywords “unsorted” and “deposited by ice” → till.Recognize moraine as a landform built of till, not the sediment name.Exclude meltwater-sorted deposits (outwash sands, varved clays).

Verification / Alternative check:
Field exposures of till show matrix-supported diamicton with poor sorting and faceted clasts, signature traits of direct ice deposition.

Why Other Options Are Wrong:
Moraine — geomorphic ridge or blanket of till, not the generic material term.Glacial sand — typically meltwater-sorted and stratified.Varve clay — annual lake-bed layers, distinctly laminated.

Common Pitfalls:
Using “moraine” and “till” interchangeably; one is a landform, the other a sediment.

Final Answer:
till