Correction: The first stage of New Glenn carries only about 260 tons of methane. The 1150 tons is the full propellent load, liquid oxygen and liquid methane combined.

The heat from combustion of this amount would be about 3.4 kt, which is roughly the same as the heat in the late fireball of the Trinity test.

The mushroom cloud from the New Glenn explosion was also substantial: https://photos.app.goo.gl/a7uPVjsB5n453SJA7