An earthquake cracks open the Sinila volcanic crater on the Dieng Plateau, releasing poisonous H2S gas and killing 149 villagers in the Indonesian province of Central Java.

An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.

A volcanic crater is an approximately circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During volcanic eruptions, molten magma and volcanic gases rise from an underground magma chamber, through a conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as lava. A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of explosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as a caldera.

The Dieng Plateau, often called simply Dieng is a plateau in Central Java, Indonesia that forms the floor of the caldera complex on the Dieng Volcanic Complex. Administratively, this plateau is included in the territory of Banjarnegara Regency and Wonosobo Regency. It covers agricultural areas that have a subtropical climate with high levels of rainfall.

Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian and Pacific oceans. Comprising over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guinea, Indonesia is the world's largest archipelagic state and the 14th-largest country by area, at 1,904,569 square kilometres. With over 280 million people, Indonesia is the world's fourth-most-populous country and the most populous Muslim-majority country. Java, the world's most populous island, is home to more than half of the country's population.