-ea- Look up -ea- at Dictionary.com
digraph introduced early 16c., originally having the sound of long "a" and meant to distinguish words spelled -e- or -ee- with that sound from those with the sound of long "e"; for example break, great. Since c.1700, the sound in some of them has drifted to long "e" (read, hear) or sometimes short "e" (bread, wealth).