In Ethereum, the difficulty bomb is a mechanism programmed into the blockchain protocol to make mining impossible after a certain date. In 2015, Ethereum added the difficulty bomb as a way of pressuring its community to transition from proof-of-work (PoW) to proof-of-stake (PoS). When the difficulty bomb goes off, it will increase the block time, slowing the network. At that point, incentives to maintain PoW will vanish, and mining will cease on the network. The subsequent mining freeze is being referred to as the Ethereum Ice Age. In a nutshell, the Ice Age is a mechanism to force Ethereum to transition to the PoS consensus mechanism.