If it is pavement or concrete, Sika makes a product that will seal up the cracks.Click here for website
The movement is severe though and it should be replaced with concrete and reinforcing wire. This is only a fix until it cracks elsewhere.
It is a self leveling product that will fill the crack, seeping into the smaller areas filling those too. So it does not make a thorough mess, after the tip is cut small enough to fit into the crack all the way to the bottom, and squeeze the trigger to fill the crack from the bottom up. You can add a small tube to extend the tip a few inches, but make sure you have it secured very well, for if it falls off you will have a real mess on your hands! The only down side to using this material is small voids under the surface, it will flow into them and waste material.
The way to combat this is to take DRY, free running fine sand and fill the crack half way up, Dry sand will fall to the bottom and not hang on the sides. Use a paint brush to level out the sand in the crack. This complicates the application of caulk but with care, you can still pull it off, just govern how far down the tip goes in so it does not plow the sand as you move the tip of the tube along the bottom of the now half filled crack. Do not try to fill it all at once, fill it to the top as you move it along, but it will always settle in more. Give it time to settle after the initial fill then top off afterwards, preferable before it sets.