MOABs short for Massive Ordnance Air Blast, or more sarcastically Mother Of All Bombs is designed to take out large targets of structures and equipment. It also works for tunnel invasion and destruction of equipment stored underground. It does not work well to collapse tunnels. They are primarily effective due to air pressure changes of causing casualties and detonating bombs and explosives stored both above and below ground in tunnels and such. The blast is designed to make stuff move causing the damage as they roll and fly around with the blast impact. That also hurts stuff alot. The effective blast radius is reportedly about a mile or a 2 miles wide circle. Side note-- the Russians have built a bigger one nicknamed FOAB or Father of All Bombs.
The Daisy Cutters are of a similar design but smaller, IIRC about a gross weight of around 15K lbs. MOABS is right at 21K. I suspect both are quite capable of causing substantial damage to trees and bushes in an area and clearing the outer part for helicopter landing. It would be not to close to center due to likely stumps and uneven ground and not to far out due to piles of fallen timber and flying debris from chopper downwash.
Understand this all is based on general knowledge due to an interest in blowing stuff up with no personal experience playing with one. Or playing with big stuff that blows up.
Reportedly it was used for the shock and awe effect of anyone well outside the area seeing the blast and effect and saying-- Oh Chit, whadda we gonna do now? That would have a much better psychological efffect than a half dozen B-52s laying carpet.
Nemo
There are several other Youtubes on MOABs. Click the link below. But watch below that first.
N
http://www.youtube.com/results?search_query=MOAB+-+Mother+of+All+Bombs+GBU-43%2FB