Glassing

"You are, all of you, vermin! Cowering in the dirt thinking... what? That you might escape the coming fire? Your world will burn until its surface is but glass!"

— Unidentified Covenant

Two Covenant CCS-class Battlecruisers glass Earth in the Second Battle of Earth.

Glassing 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 and uninhabitable. 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.

Sometime during the Second Battle of Earth, Earth is being glassed, as confirmed in the Halo 3 E3 2007 Trailer.