What are the two main processes of glacial erosion and how do they work?

Firstly it is important to understand what erosion is. This is when exposed rocks are broken down by water, wind or ice and the product of this is transported away in one of the aforementioned mediums. It is important that you remember to distinguish this from weathering where no transport occurs.

To understand processes of glacial erosion is important in geography as they are present from GCSE to university level! There are two main types known as plucking and abrasion. 

Plucking occurs when a glacier freezes to the substrate (probably rock or sediment) beneath it, as gravity continues to drive the glacier downslope it rips  the substrate that it has frozen to away and transports it downglacier (talk about transport processes if required). 

It is easiest to think of abrasion as a giant piece of sandpaper. Rocks and sediment entrained in the base of the glacier are dragged over the underlying bedrock and this causes the bedrock to be worn away. This is often shown by 'striations' and 'polished surfaces'.

(Can go on the give example of freeze thaw weathering and explain why it is different to help improve understanding).