A powerful earthquake has hit the Caribbean island of Haiti.
Thousands, of people are feared dead. So why has this quake been so destructive?
Haiti is very poor
A quake of this power would cause lots of damage wherever it hit, but Haiti was especially vulnerable.
Haiti is the poorest country in the western half of the world, meaning it hasn't been able to prepare for big earthquakes.
Rich countries in areas where quakes happen can afford to make buildings which can handle quakes better.
But in Haiti, there are lots of badly built structures, which fell over easily.
Where the quake happened
The epicentre of the quake, which is where it was strongest, was just 10 miles from the capital, Port-au-Prince.
On top of that, the epicentre was five miles underground.
That is quite shallow for a quake, and the closer to the surface the epicentre is, the more shaking it causes at ground level.
After large quakes, there are often smaller quakes called aftershocks.
The Haiti quake reached 7.0 on the Richter scale, which measures the strength of tremors.
Following that, there were more than 10 aftershocks measuring more than 5.0 on the Richeter scale, each causing more damage.
Haiti is regularly hit by hurricanes, which means people there have experience in dealing with large natural disasters.
Aid is being sent in to the area, and several countries have offered money to help Haiti.