Similar to Oklahoma City Bombing
The most well-known and highly publicized incident illustrating the devastating effects of an ammonium nitrate explosion was the Oklahoma City bombing in 1994. That explosion involved one hundred 50 pound (23kg) bags of ammonium nitrate, a total of 5,000 pounds. To put the West, Texas incident into perspective, the plant stored 270 tons of ammonium nitrate or over 100 times as much as was used in the Oklahoma City bombing. It is estimated the West, Texas explosion was the equivalent of between 1 to 5 tons of TNT.
A one ton TNT explosion creates an earthquake-like event of 2.0 on the Richter scale. See 1 ton TNT explosion in second video below!
Ammonium Nitrate Engulfed in Fire
According to reports a West fertilizer building containing ammonium nitrate became completely engulfed in fire and this may have led to the explosion. Another possibility was the presence of anhydrous ammonia, a key component used to make ammonium nitrate; when anhydrous ammonia is mixed with water a chain reaction occurs leading to an explosion.
Ammonium Nitrate Explosions Happen Frequently
The worst industrial accident in US history occurred in 1947 when ammonium nitrate was detonated aboard the ship in a Texas port killing 600 people. In terms of the total amount of human and property destruction the West, Texas explosion may come to rival the 1947 event.
The long history of the handling of ammonium nitrate, stretching back half a century, is littered with devastating explosions that have destroyed property and taken lives all across the globe. The amount of damage inflicted in these events is directly proportional to the amount of fuel burned or the total energy available, the maximum flame velocity, and way in which the combustible gases are stored.
1 TON TNT = 2.0 on Richter Scale. Richter Scale and TNT Equivalents
- 2.0 on Richter Scale = Approximately 1 ton TNT or 450 kg of dynamite (World War II Conventional Bomb)
- 2.5 on Richter Scale = Approximately 4.6 tons of TNT (World War II Blockbuster Bomb)
- 3.0 on Richter Scale = Approximately 29 tons of TNT (Massive Ordinance Blast)
- 3.5 on Richter Scale = Approximately 73 tons of TNT (Chernobyl Nuclear Disaster)
The following video shows an explosion of 1 ton of TNT. The West, Texas explosion is estimated at between 1 and 5 tons of TNT.
Forensics investigators caution it is too early to determine the exact cause but noted two major classes of incidents involving ammonium nitrate. First, anhydrous ammonia, stored in liquid form becomes a vapor which when mixed with air is extremely explosive. Second, ammonium nitrate, stored at the facility, could have exploded.
Deflagration, meaning to burn down, describes the rapid high energy combustion event that propagates through gas or other combustible material at subsonic speeds and is driven by heat transfer
Seismology and Explosions
Seismologists use the Richter scale to measure the size of earthquakes in terms of the energy released. The reading is a combination of a measure of the rigidity of the earth multiplied by the average slip and the size of the slip area.