There are three main types of plate boundary: divergent, convergent and transform. Plates move away from one another at divergent boundaries. This happens at mid-ocean ridges. Plates move towards one another at convergent boundaries; one plate is forced below another in a process called subduction.
The skin of a Concord grape is typically dark blue or purple, and often is covered with a lighter-coloured epicuticular wax bloom that can be rubbed off. It is a slip-skin variety, meaning that the skin is easily separated from the fruit. Concord grapes have large seeds and are highly aromatic.
The Concord and the Niagara varieties of grapes are both North American in origin. Concords are blue in color, and do not have a reddish glow in the sunlight when ripe. It is a bit more difficult to tell when a Niagara berry is ripe.