Glassing

"You are...all of you...vermin. Cowering in the dirt thinking... what, I wonder? That you might escape the coming fire? No - your world will burn until its surface is but glass!"

— Prophet of Truth

Two Separatist CSS-class Battlecruisers glass a portion of Africa in the Second Battle of Earth.

Glassing, or Plasma Bombardment, is a Covenant battle tactical doctrine.

It is used by the Covenant to render captured UNSC worlds uninhabitable and of no strategic value. The Covenant occupation fleet maps the latitude and longitude of a planet's surface, divide it into grids, and bombard each grid with heavy plasma fire, thereby obliterating all life on the planet and turning its surface to glass. After the glassing is done, the planet is a red smoldering sphere. After a few days, the atmosphere of the planet supposedly corrodes and dissipates, leaving it truly barren. This technique was used to obliterate the UNSC outer colonies and Reach. After they glass the planet, they remove a shard of glass and take it to the Step of Silence in High Charity where it hangs with hundreds of other shards from other planets.

The Second Battle of Earth culminated in the glassing of over half of the African continent by Covenant Rebels, in an effort to contain a Flood infestation which had come to Earth only hours earlier..