Is it normal my mom gets extremely angry?

My mom gets episodes of extreme anger, during while she yells, swears, and breaks things, like smashing the phone and throwing the dishes on the floor. Growing up she would chase me around the house trying to hit me and once threw a plate at my head.

The thing is, most of the time she is a very nice person. Most of my friends really like her, and she is very friendly and generous. But when she gets angry, she is completely out of control. She's slapped my grandma, screamed at guests until they had to leave, and called my friend's mom a fat bitch to her face. When she is emotionally out of control like this she can also become extremely depressed, crying in her bed about how she "doesn't want to be here."

I know a lot of people get intense emotions once in a while, but this seems pretty extreme. Am I overreacting or is something wrong? If something is wrong, does anyone know what might be going on?