ALPINE - Contractors are working to clear debris from the worst rock slide on the Palisades Interstate Parkway so far this year.

Massive rocks slid off the cliffs of Palisades Interstate Parkway in Alpine over the weekend, and landed on Henry Hudson Drive.

The massive boulder is too big for the equipment of the parkway commission’s crew. The excavator can move up to 5 tons, but the boulder is estimated to be at least double that.

A contractor with heavier equipment will be brought in to break up the boulder, move it and open up the roads.

Officials say the rocks go back to when dinosaurs roamed, so there is no way to tell when they will fall or why they will fall.  

"We have a number of instances, I would say annually. I would say smaller one or two rocks about the size of my desk possibly.  There are other times when you get more material coming down," says Alpine Assistant Superintendent Chris Szeglin.

The latest incident actually only falls in the middle of the scale. About 20 years ago, an entire column plummeted down and there was no road left.

While rockslides are common, officials say that they have seen more this year and don't know why.

Officials are hoping to get the road cleared in the next few days.

No one was hurt when the boulders fell.