© Denys, Wikimedia Commons
The Tunguska blast affected hundreds of square miles of northern Russia.
109 years ago today, a meteor crossed paths with Earth and blew apart in the air above a remote area of northern Russia, near the Tunguska River, on June 30, 1908.

Wind from the blast flattened trees for hundreds of miles, and the shock wave it sent through the ground would have registered a 5.0 on the Richter scale. The dying meteor exploded with a force estimated to be on par with the earliest nuclear bombs, around 15 megatons, although estimate range from 3 megatons to 30. (It's hard to say much for sure about the Tunguska object, because it left no crater, and no fragments have ever been found -- though not for lack of searching.) It could have flattened a major city. Fortunately, it struck in a remote area of the Russian taiga.

The director of the meteorological observatory at Irkutsk, whose seismographs recorded the impact, gave questionnaires to witnesses in the region and published a collection of their responses in 1924. Locals describe a fireball in the sky, multiple thunderclaps, a blast of heated wind, and a rumbling of the Earth.

The head of the Znamenskoye village post office actually saw the meteorite fall, and he later reported, "A falling aerolite was noticed, approximately to the south-west from the village of Znamensky. A fiery strip was visible. The sky was absolutely clear. There was a strong thunder in the end, with an explosion."

According to GK Kulesh, a local schoolteacher who may also have worked at the meteorological station, some people thought the world was ending. Busy in his office, Kulesh just mistook the meteor impact for a military exercise:
The fire pillar was seen by many, and its shape in the form of a spear is also known. The smoke or the gray cloud, which later passed into the dark, was also noticed by many. I could not ascertain when the glass was shaking in houses: during strokes, before or after them. The strongest blows were the last, and the concussion of the hot air was strong. [...] The peasants of this village were so overwhelmed by the blows that they sent a deputation to the local archpriest to ask if the Apocalypse begins, so as to prepare for it in Kirensk. That there was a concussion of the ground, which I could conclude from the fact that the barograph noted a line on the tape, and I firmly remember that no stranger entered the room, and I did not get up from my place, so I could not push the device. I heard the blows, but since the windows were covered to the northwest, and opened only on the south, I took the blows for volleys of rifle shots in the military field.
A worker on the Siberian Railway reported, "I heard a sound like dynamite exploding rocks and repeated shots of the big guns, with a terrible crash and frequent noise, passed from west to east, and toward the north."

Others described the feeling of the impact as "A strong underground rumble like thunder peals," or, in the words of one meteorological officer, "terrible thunder in a clear sky, like a cannon."
© Vokrug Sveta
Trees flattened by the Tunguska blast.
The meteor impact uprooted and flattened trees for over eight hundred miles. A resident of Krasnoyarova village wrote:
The weather that day was clear, the air for breathing was heavy. [...] There were sounds, resembling sounds from guns with interruptions, in the direction from west to north. At first, the sounds were heard more often, five minutes later, then less and less often. The blows continued for 1.5 hours. The number of strokes could not be counted. In this direction, where shots were heard, the sky was a little darker. [...] Some expected a raincloud. The strikes were declared thunder. [...] In the same year and month, the date is unknown, from the Tunguska River 15 miles along the Ayan River, there was a large strip of uprooted forest along the road for 1 mile. There are many witnesses of this in the village of Krasnoyarovskogo, dealing with Tunguska, including myself.
And foreigners passing through the area told locals, "a strong air pressure stripped out a strip of forest and several head of deer were killed."

Those who didn't see the meteor fall weren't quite sure what to make of the rumbling earth and blast of hot wind. In a nearby village, one quick-thinking observer felt the impact, but ruled out an earthquake.
Yesterday, June 17, 1908 (Tuesday), while in the yard, I heard from the north-eastern side of the horizon, a loud noise, or a rumble like thunder. It lasted about 2 minutes. I quickly went into the house to observe the time; it was 7:27 AM (local time). During this hum the air came in a concussion, as if from the wind. The sky was cloudless. The sun was shining brightly. I began to observe the hanging objects, but they were calm. From this it can be seen that there was no earthquake during the rumble. Then, for a period of at least 15 minutes, a weaker rumble repeated at intervals, whether it was an underground rumble, or some other, I can not determine. The population of the city and the surrounding villages are surprised.
On a July 5, a local police sergeant wrote in a letter that he felt nauseous just before the strike, a symptom some people report before earthquakes.
June 17 at about 8 am I sat on a bench near the gate. Suddenly I felt uncomfortable -- there was a nausea, as I remember happened to me in 1906, when there was an earthquake. It was exactly the same with me at that time, but I did not pay attention to the motion of the ground, and took a seat on the bench, and at that moment there was such a thunderbolt that the windows were rattling in the house, then a second and third of the same blows. The strikes lasted a short time, and these strikes turned out, in my opinion and precise definition, straight from the station Ingash to the northeast, and seemed quite close. The roll of these blows came with a great noise on the surface of the earth to the south. In the yard the weather was clear, but slightly 'blizzard,' i.e. it seemed like a fog, and I expect that it was just smoke. In the house the family slept.
If the sergeant's report is accurate, some people really can sleep through anything.

Shortly after the Tunguska incident, a scientific expedition searching for pieces of the meteorite interviewed local witnesses. You can read more of their accounts of the meteor strike here.