Features of Glacial Deposition

Firstly, what do glaciers have to deposit? As a glacier moves it tears off huge amounts of rocks and other material from the valley surfaces. This material becomes embedded within the glacier and is sorted into different layers depending on the size of the material. The material carried by the glacier is called moraine. There are 4 different types of moraine; Lateral Moraine Medial Moraine Ground Moraine Englacial Moraine

Lateral Moraine: This is the material carried at the top of a glacier or ice sheet at its sides. The material may have been derived from plucking of the valley sides or from freeze thaw action on the valley sides. When the ice melts, lateral moraine forms a ridge along the valley.

Medial Moraine This is material transported on top of the ice sheet in the middle. It is formed when 2 glaciers have joined together and their lateral moraine merged. If a glacier has many large tributaries joining it, many lines of medial moraine form.

Ground Moraine This is material carried along the base of the ice The material has been plucked from underlying rock. Most of the material is then abraded to become tiny particles called rock dust When the glacier begins to melt it deposits the moraine.

Englacial Moraine This is material carried inside the moving glacier The material may be derived from surface moraine which has fallen into or been washed into crevasses

diagram of glacier

Features of Glacial Deposition Teriminal Moraines Recessional Moraines Boulder Clay Plain Drumlins Erratics Moraine-Dammed Lakes Kettle Holes

Terminal Moraines: These are formed where ice melts and deposits all the moraine it was transporting at the front of the glacier (snout). The ice sheet/glacier is still moving so material is constantly being added to the terminal moraine The longer the ice continues to melt at the same place, the higher the terminal moraine Its material will include lateral, medial and englacial moraines, ground moraine and any loose rocks and soil bulldozed in front of it Therefore, terminal moraines are completely unsorted They may extend for many kilometers They mark the furthest point reached by the ice sheet or glacier

Terminal Moraine

Drumlins: These are hummocky deposits of boulder clay They are 100 – 800m long and 25 – 100m high and oval shaped The side of the drumlin facing upvalley is steeper than the downvalley side. Hummocks may build up because ice pauses in its retreat or because there is a slightly larger amount of moraine at that point The hummocks then become streamlined by the moving glacier flowing over it They are usually found in groups or swarms

Kettle Holes These were formed by isolated blocks of ice melting more slowly than the rest of the ice-sheet The melted ice leaves behind boulder clay When the block of ice finally melts, the meltwater is trapped by the boulder clay surrounding it This leaves small, round kettle holes

Annotated diagrams may be used. Task 1: Using the information that you have just heard and your notes, answer the following question; Select one feature of glacial deposition and explain the processes involved in the formation of this feature. Annotated diagrams may be used. 3 marks