The Tunguska Event, the largest impact event on Earth in human recorded history, resulting in a massive explosion over Eastern Siberia.

The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. The explosion over the sparsely populated East Siberian taiga felled a large number of trees, over an area of 2,150 km² (830 sq mi) of forest, and eyewitness accounts suggest up to three people may have died. The explosion is attributed to a meteor air burst, the atmospheric explosion of a stony asteroid about 50–60 metres wide. The asteroid approached from the east-south-east, probably with a relatively high speed of about 27 km/s; 98,004 km/h (Mach 80). Though the incident is classified as an impact event, the object is thought to have exploded at an altitude of 5 to 10 kilometres rather than hitting the Earth's surface, leaving no impact crater.

An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, as the impacting body is usually traveling at several kilometres per second (km/s), with a minimum impact speed of 11.2 km/s (7.0 mi/s) for bodies striking Earth. While planetary atmospheres can mitigate some of these impacts through the effects of atmospheric entry, many large bodies retain sufficient energy to reach the surface and cause substantial damage. This results in the formation of impact craters and structures, shaping the dominant landforms found across various types of solid objects found in the Solar System. Their prevalence and ubiquity present the strongest empirical evidence of the frequency and scale of these events.

Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is at least somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers, and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanoes, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation.