What is a shelf cloud?

The weather system was captured at Lake Superior, Michigan, in the US. source: https://ift.tt/2NkCv2C #Headlines by: Original Post: https://ift.tt/2NkCv2C https://ift.tt/2IMOjax
source: https://droolindognews.blogspot.com/2018/07/what-is-shelf-cloud.html