Saw that happen to my friend's maple tree... they had this perfect volcano of mulch that looked so tidy. All it did was trap moisture and hide those girdling roots until the whole thing started leaning. Took years off that tree's life for sure.
Read that mulch volcanoes are a common mistake in suburban landscaping. They create a wet environment that rots the bark and strangles the roots. It's sad how many trees die from such a simple error.