Glassing

"You are...all of you...vermin. Cowering in the dark 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 a portion of the African continent by Covenant Separatist, in an effort to contain a Flood infestation which had come to Earth only hours earlier.. Lord Hood accuses them of glassing half of the continent, but given his distaste for his former enemies, he may have been exaggerating about the actual extent of the glassing. This is supported by the fact that the area around Killimanjaro seems relatively intact during the ceremony at the end of the game.