AFTER A LONG TRIP ON DIRT I always check and clean the air box and the air filter.
If the dust is so plentifull consider a new filter element.
The dust in the matrix indicates your element has been compromised
I have recently returned form the November BMWCMCC West Coast Tour.
This is what my air filter and box look like after a 1200km run through sand and dirt.
Be sure to follow the owners book guide and vacuum all air from the airbox and suck out any dust from the filter.
If in doubt- replace the filter.
Andyman
Yup that's me. Standing up in the traffic on the 1150GSA.