In any glacial movement, the underlying rock and earth is modified in some way. Erosion by glaciers can modify rock in two ways:

In a process called plucking, meltwater moves into cracks present in the bedrock and is able to refreeze (5). This freezing action will cause the rock to break and dislodge from the bedrock, and can even freeze these rock particles to the base of the moving glacier (5). The rock within the glacier can now grind against the rock it is moving over, creating abrasions, which is the second type of glacial erosion. Abrasions are more pronounced where the glacier is thicker, thus creating a greater pressure on the underlying rocks (6). Such striations are an indicator of the direction in which the ice moved (5). Any powder that is produced from the grinding of rock is called rock flour and is composed of very fine particles (6). Meltwater has a tendency to wash away this rock flour and carry it into streams and lakes, which gives the water a milky green colour (6).

The degree of erosion depends on ice velocity, ice mass and the amount of rock debris it is carrying, not to mention the type of rock it is moving over. (6)

Valley glaciers will carve into valleys creating glacial troughs which have steep bedrock walls and flat floors. As the glacier recedes, sediment will fall from the valley walls and alluvial fans are created, giving the valley a U shape (see Figure 2). (6)

Cirques

The head of the valley, carved out by the glacier is called a cirque. A large amount of snow accumulates on a mountain, turning into a glacier. Due to the weight of the ice and the force of gravity, the glacier rolls over the threshold and down into the valley, carving a half-circle shape into the mountain. The ice alone does not carve the mountain wall, but falling rocks can also grind against the wall by falling into crevasses and being dragged by the glacier ice. (6) 

Erosion by Ice Sheets
Ice sheets, though they also erode underlying rock, produce a different result than valley glaciers. Ice sheets tend to produce a smoother, streamlined effect on the rock. Though erosion works the same in both cases, ice sheets will scour and smooth the landscape rather than deeply grinding and gouging it. (6)

 

As glaciers move, they drag rock particles along with them, carrying a collection of different sized rocks from dust-sized to boulder-sized, which are all mixed together. This rock collection carried by glaciers will eventually be deposited somewhere else and is called till. Glaciers have the "strengh" to move gigantic pre-existing boulders from one place to another, and these large masses of rocks are known as erratics, and can also be an indication of the direction of glacier movement. (6)

Moraines
A collection of till that has been carried by and deposited by a glacier is known as a moraine. There are three types of moraines: lateral, medial and end moraines. Lateral moraines consist of elongated low mounds of till that form along the sides of a valley glacier, often by the accumulation of fallen rocks along ice edges. A medial moraine is formed when adjacent glaciers come together and the moraines joing along the same path. End moraines are ridges of debris which has accumulated along the front edge of the glacier. (6)

Picture this! A medial moraine is like the slab of concrete separating the highway from the on-ramp. The on-ramp road and the highway are merging and moving in the same direction, but there's that small slab of concrete that separates them for a short distance before turning into that dotted line of the lane. In this scenario, each lane of the highway would represent the moving glacier with moraines (dotted lines) as lane dividers!

 

Did you know? These till deposits are an excellent source of aggregate to make concrete and roads from! (6)