Around seven o'clock on the 30th June 1908, there was an explosion just above the ground in Tunguska that saw thousands of trees and land damaged for miles around. It is believed to have been an asteroid or a meteor. The fact that there was no crater means that the object didn't actually hit the ground but exploded above the land. Fortunately, as the area is a remote part of Russia there were no human fatalities. It remains as a mystery as to what actually happened as there was no eye witnesses to the actual event. Some theorists believe it might have been an alien spacecraft that blew up. Even though England was miles away, the explosion was felt by meter readings. At that time, nuclear bombs had not yet been invented and so a man made explosion was discounted. The explosion had the power many times greater than the hydrogen bomb that was dropped on Hiroshima and Nagasaki.
It was not until 1921 that the first exploration of the area started, Leonid Kulik who was the chief curator of the meteorite collection at St. Petersburg museum led the first exploration to the area. He had to turn back because of the conditions of the area. He returned in 1927 but was this time more successful in getting to the area. When he interviewed people who lived there, they refused to speak, saying it was the act of their god, Ogdy. He did eventually manage to speak to someone who described it as :-
Suddenly in the north sky, the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire. At that moment there was a bang in the sky and a mighty crash. The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled.1
There was no deaths amongst the human population but millions of trees were destroyed and thousands of reindeer were killed.
The fortunate thing is that it was in an area of such low human population, had the object smashed into a city such as London or New York, the death toll would incalculable. Not only would those in those cities would have died but the knock on affect would have been immense. According to NewGeography website, only about 2.7% of the world's land is occupied by urban development. Therefore, it is highly unlikely an asteroid would hit such a small target. We are constantly being bombarded by meteors in the upper atmosphere and for most, they will burn up and those that do make it to the ground are small. N.A.S.A. constantly watches the skies along with other agencies such as ESA to keep an eye out for Near Earth Objects that could hit us. Before you go screaming and saying 'The World is Nigh', the chances are 2.7%, quite a small figure. 2. The Apophysis asteroid will pass closer to Earth than the height at which satellites orbit the planet.
On 15th February 2013, an asteroid hit the Russian city of Chelyabinsk and showered the area with meteorites. There was no deaths caused by the impact but there are many reports of damage and injuries. Russia is the largest country in the world which explains why they've been unlucky at being hit twice with such prominence. The below map shows where the city is.
This video below produced by NASA and hosted at Youtube will give some detailed information on the incident.
With the advent of the Internet and Video Cameras, the Chelyabinsk event was captured and shown round the world. The meteor in this case didn't explode like Tunguska but broke up into small parts and crash landed in the area. As it was February, the area was covered in snow and meteor fragment as well as being small were not easy to spot. Sure, you could see the impact they made in the snow but they were hard to find. Meteor hunters from across the world descended on the city to collect and analyse, both experts and amateurs. The video below is a collage of videos of the incident, many from car video cameras.
It had managed to hit the Earth because the object wasn't being tracked by the relevant agencies. There are literally hundreds or thousands of the objects and not all can be tracked, size wise and financial costs.