My 11 mth old Golden Retriever is dramatically shedding mive clumps of her thick coat...is that normal?

I mean....MIVE amounts. She is not scratching, she is perky and acting normal, and her nose is wet and cold. The only thing going on is the hair loss issue. When she is running in the yard, clumps of her thick coat are flying off her. It looks crazy so I am of course paranoid. When I pet her, I'm left with a handful of fur. However, there is a very much darker coat still remaining underneath, which is not as fluffy and soft, and kind of a bit wirey, but not mangey-like (I am pretty sure). I am hoping someone else's dog has gone through this...I guess to validate my simple explanation of "she is just losing her puppy coat." Anyone??