Cupped out whoops?

Dirt compound is a big factor. But, whoops do get cupped in soft clay as well as hard packed. I feel like you see a lot more hard packed whoops cupped out as they aren’t as easy to touch up and don’t break down as fast. It’s usually the top third of the whoop getting a “indentation” due to the front wheel and black wheel slamming into it while the real wheel is more times than not accelerating. 

Cupped whoops ... 

And indentation in the whoop face caused by the removal of dirt from repeatedly tires eating away at the dirt. Where a grove or rut will develop on the face of the whoop, whereby causing an inconsistent forward drive. The resulting action may be in either a side deflection in the case of a vertical rut on the face, or a pointed sharp peak in the whoop in the case of a horizonta cupping which can cause an unexpected vertical force propelling the machine skyward. 

Thank you for your question. 

Where the rear tire hits each whoop it digs it out a little bit. It results in the top foot or so of the whoop being almost vertical. Picture does not do it justice. Starting to get cupped out. 

Side profile view

Normal whoop on top

Cupped out on bottom

Not sure where this was at but assuming somewhere that has a mix of fast guys. I notice that at supercross that cup section is way higher on the whoops vs like your picture and what I've seen at other tracks.

Goes to show that's how those guys can hit them so fast they are just skimming them so high on the whoop, crazy.

You are spot on. Wide range of speeds there that day. Guys clipping the tops to amateurs just trying to learn and survive. The pic is a little deceiving as the vertical cup is really only a few inches below the top. even the really fast guys have the rear tire drop down a bit on some whoops and just skim the top on others. Anyway you look at it, the talent to go through those when they are beat up is insane and beyond anything I'd even want to try. Seeing it up close gave me even more respect for what they are capable of doing on a bike.

They should have a pit reporter like JT give an explanation of it on camera from the whoops.

Go to 3:20

Imagine when jumps get those "kickers" on the face/takeoff. It can kick your rear wheel up causing an endo and can unpredictably kick the rear wheel around. When trying to blitz the whoops, it will kick the rear wheel up not only up (causing an endo) but sideways, like when you saw Hunter's rear wheel get thrown left & right. The pics/videos and explanation above do a pretty good job of describing them. As a rider, they are absolutely terrifying. 

The crazy thing too is there's no easy or simple way of learning how to ride the whoops. When I was still riding on my KX85, I pretty much just had to grip it and rip it. I still remember clicking up into 4th gear, leaning back and into the "attack" position on the bike, and praying to God lol. It's one of the most scary and yet satisfying things you'd ever do in your life. Nothing quite feels like blitzing a set of SX whoops.