Steps. 1  1. Perform major pruning during the dormant season. The ideal time to prune a crabapple tree is late winter or in the cold days of early spring, before leaves appear. 2  2. Remove suckers. Suckers are additional branches that begin growing underground and sprout near the base of the tree. 3  3. Remove water sprouts.
The upper crust is 12.5 km thick in crust with an average total thickness of 40 km (ref. 3). If the upper crust is the product of 14% melting, the corresponding residue would be 77 km thick, resulting in a total crustal thickness of 100 km, including the middle crust.
The average age of the current Earth's continental crust has been estimated to be about 2.0 billion years. Most crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth and so are not readily destroyed by subduction.