What Would Be the Global Fallout If a Single 100-Megaton Bomb Was Detonated?

The Most Powerful Weapon Ever Conceived—What Happens If It Goes Off?

Imagine the detonation of a single 100-megaton nuclear bomb—twice the size of the largest bomb ever tested, the Soviet Tsar Bomba. Such a blast would dwarf all previous explosions in scale and consequence. Though no country currently deploys a bomb this size, the theoretical implications are staggering.

From the immediate destruction to long-term fallout, a detonation of this magnitude—especially over a populated area or even as an airburst over the ocean—could trigger effects on a continental or even global scale. Let’s explore what such a catastrophic event might look like in reality.

Immediate Blast Effects

The explosive yield of 100 megatons of TNT is equivalent to 100,000,000 tons—roughly 5,000 times more powerful than the Hiroshima bomb. If detonated at optimal altitude (around 4–5 km), the effects would include:

• Fireball radius: 10–12 kilometers (vaporizes everything)
• Severe blast damage: 30–50 kilometers (destroys buildings, infrastructure)
• Thermal radiation burns: Up to 100 kilometers away (3rd-degree burns)
• Shockwave glass breakage: 500–800 km radius depending on terrain

Entire metropolitan areas would be obliterated. A single bomb of this size over New York City or London would kill millions instantly and injure millions more, overwhelming every medical and emergency system on the continent.

Radiation and Fallout

While an airburst reduces local fallout compared to a ground burst, the sheer scale of a 100-megaton detonation ensures some radioactive debris is injected into the atmosphere regardless. If the bomb were detonated near the surface—such as in a city or underground facility—the fallout would be catastrophic.

• Ground burst: Pulverizes earth and buildings into radioactive dust, which is carried by wind currents
• Stratospheric injection: Fallout particles can circulate the globe for months or years
• Hot zones: Fallout patterns depend heavily on wind; areas downwind could receive lethal radiation for hundreds of kilometers

A 100-megaton ground burst could generate lethal fallout downwind for over 1,000 kilometers, contaminating everything in its path—soil, water, air, and food.

Environmental and Climate Consequences

In addition to blast and radiation, a detonation this size would inject vast amounts of soot and particulates into the atmosphere, especially if it ignites large urban or forested areas. This could lead to what is known as “nuclear autumn” or, under extreme conditions, nuclear winter.

• Black carbon: Released from fires and smoke, it can block sunlight
• Surface cooling: Even a single bomb could cool temperatures slightly on a regional scale for weeks to months
• Ozone depletion: EMP and radiation can damage the ozone layer, increasing UV radiation levels

The long-term agricultural and ecological impacts would depend on where the bomb was detonated and the weather patterns in the following weeks. A detonation in a high-fire-risk area (urban or forested) would have far more atmospheric consequences than one over open ocean.

Geopolitical Shockwaves

Even a single use of a 100-megaton bomb would fundamentally alter the world order. Whether used in war or as a “demonstration,” it would almost certainly trigger one or more of the following:

• Mass panic and global market collapse
• Worldwide condemnation and possible retaliatory strikes
• Collapse of treaties like the NPT and CTBT
• New arms race in “superbombs” and space-based defense systems

The psychological effect alone—witnessing a single bomb destroy an area the size of a small nation—could cause a global reevaluation of nuclear deterrence and human survival strategies.

The Tsar Bomba Precedent

The Soviet Union’s Tsar Bomba, detonated in 1961, remains the largest nuclear explosion in history at 50 megatons. It was a test bomb, intentionally “dialed down” from its full 100-megaton capability.

Even so, it created a fireball eight kilometers wide, a mushroom cloud 60 kilometers tall, and shattered windows over 900 km away. Had it been a ground burst, the fallout would have reached mainland Europe.

A 100-megaton bomb is no longer fantasy—it was once built. Its power has already been proven on a smaller scale. We now understand that scaling up makes these weapons exponentially more destructive, not linearly.

Would It End the World?

No single bomb, no matter how large, would end civilization. But a 100-megaton detonation would test the boundaries of what modern society can endure.

It would destroy cities, pollute entire regions, disrupt climate systems, and provoke geopolitical chaos. It would forever change how we think about war, peace, and planetary vulnerability.

In a world where even 1-megaton warheads are considered “overkill,” the 100-megaton bomb stands as both an engineering marvel and a moral warning—a relic of what we could build, but must never use.