What caused the 2004 Tsunami?

The 2004 ocean earthquake and tsunami was as bad a recent natural disaster as there has been in terms of recorded fatalities.  This was truly a world disaster; deaths were recorded as far away as South Africa, 5,000 miles from the epicenter of the event.  The tsunami was caused by a huge ocean earthquake, over 9 on the Richter scale, which in turn caused a massive ocean wave to form.  Many people in the islands surrounding this epicenter were killed by the destruction caused by the earthquake itself; many more died when the waters hit their homes.

A tsunami gains momentum and energy as it moves across the ocean at very high speeds, and as it reaches shallower waters, the wave slows in velocity and grows in height as it hits land.  In some places, the wave would have been some 100 ft in height by the time it hit the beaches of Southeast Asia, with devastating consequences, unparalleled in any recent natural disaster. 

(http://geology.com/articles/tsunami-geology.shtml)

What were the effects?

The effects of the 2004 ocean earthquake and tsunami were the most terrible of any recent natural disaster, and almost unequalled in the history of world disasters.  The first and most immediate consequence was for the people of Aceh, in northern Indonesia, and the nearby Andaman Islands, for whom the effects of the earthquake were far, far greater than any weather disaster.  Many thousands of these villagers died very quickly.

The most devastating effect of the ocean earthquake, however, was the tsunami itself. “Tsunami” is a Japanese word meaning “harbor wave,” and while this is a common enough phenomenon in the Pacific Ocean, it is more unusual in the Indian Ocean, where the majority of casualties of this natural disaster were located.  The wave crashed upon the shores of several countries, and owing to the extreme poverty of many of the regions affected, the houses in which the victims lived were simply not strong enough to withstand the power of the water.

(http://www.geo-world.org/tsunami/)

How many people died?

The scale of devastation left behind by the 2004 ocean earthquake and tsunami was so great that estimates of those killed by this world disaster are still vague.  In the weeks immediately following the tsunami, it was estimated that between 250,000 and 300,000 people had been killed.  Later estimates were a little lower; but still shocking, at some 230,000 dead and missing.  This places the 2004 tsunami at the very top end of recent natural disasters in terms of devastation and deaths.

(http://en.wikipedia.org/wiki/List_of_natural_disasters_by_death
_toll#Ten_deadliest_natural_disasters)