3.5G boiled off?!?

Hello all...this is my first post...

I just collected 7G of wort from an all-grain brew....boiled for 90min....at end of boil, I was shocked to see that i was down to around 3G of wort! My boil was pretty intense, but I'm still shocked that I could boil off this much wort in90min! I was expecting around 1.5G boil off....not nearly 4!
I'm sure I could look this up in a chemistry book, but I thought you fine people would be a better way to go. Any thoughts? Am I existing outside the laws of thermodynamics?

I boil off 2.5+ in the winter for a 60 min boil, so I'd say that's pretty accurate if you had an intense boil. The average I would guess would be around 1.5 gallon an hour.

Did you use lot's of hops too?

Dude, turn the heat down. You want your boil off rate to be between 12-15% per hour. You just need a rolling boil not one that jumps out of the pot.

What pot do you have? Boil off rate is directly proportional to the surface area of the wort, so proportional to the diameter of your pot.

I boil off about 1.5 gallons in 60 minutes in a pot with a 13.5" diameter. If you are anywhere close to the same diameter, then you may be measuring incorrectly....