What is the difference between till and alluvium?
Till is the unassorted coarse and fine debris dropped by melting glaciers. The rock fragments in till are angular to sub-angular in form. It is a glacial depositional material formed directly from glacial ice.
Alluvium consists of stream deposits carried by rivers. It includes fine-sized materials like sand, silt, and clay deposited by slow-moving waters in gentler channels found in plains. Alluvium forms landforms like alluvial fans and floodplains.
The key difference is that till is glacial debris dropped by melting glaciers and is unassorted, while alluvium is fluvial deposits carried and deposited by streams.
Explanation
The textbook clearly distinguishes between these two depositional materials. Till is defined as 'unassorted coarse and fine debris dropped by the melting glaciers' with rock fragments that are 'angular to sub-angular in form.' Alluvium is described through alluvial fans and floodplains as stream deposits containing 'fine sized materials like sand, silt and clay' carried by slow-moving waters. The fundamental difference lies in their origin and sorting - till is glacial and unassorted, while alluvium is fluvial (deposited by streams/rivers).