(CNN)Here's a look at what you need to know about the earthquake and tsunami that struck Japan in March of 2011.
March 11, 2011 - At 2:46pm, a 9.0 magnitude earthquake takes place 231 miles northeast of Tokyo, Japan, at a depth of 15.2 miles.
The earthquake causes a tsunami with 30 ft waves that damage several nuclear reactors in the area.
It is the fourth largest earthquake on record (since 1900) and the largest to hit Japan.
Number of people killed:
The confirmed death toll is 15,890 as of February 10, 2015.
Japan had 54 nuclear reactors, with two under construction, and 17 power plants, that produced about 30% of Japan's electricity at the time of the earthquake. (IAEA 2011)
Material damage from the earthquake and tsunami is estimated at about 25 trillion yen ($300 billion).
There are six reactors at Tokyo Electric Power Company's Fukushima Daiichi plant, located about 65 km (40 miles) south of Sendai.
A microsievert is an internationally recognized unit measuring radiation dosage. People are typically exposed to a total of about 1,000 microsieverts in one year.
All times and dates are local Japanese time.
March 11, 2011 - At 2:46pm, an 8.9 magnitude earthquake takes place 231 miles northeast of Tokyo, Japan. (8.9 = original recorded magnitude; later upgraded to 9.0) (0:46 ET/5:46 GMT)
- The Pacific Tsunami Warning Center issues a tsunami warning for the Pacific Ocean from Japan to the U.S. About an hour after the quake, waves up to 30 ft high hit the Japanese coast, sweeping away vehicles, causing buildings to collapse, and severing roads and highways.
- The Japanese government declares a state of emergency for the nuclear power plant near Sendai, 180 miles from Tokyo. Sixty to seventy thousand people living nearby are ordered to evacuate to shelters.
March 12, 2011 - Overnight, a 6.2 magnitude aftershock hits the Nagano and Niigata prefecture (USGS).
- At 5:00am, a nuclear emergency is declared at Fukushima Daiichi nuclear power plant. Officials report the earthquake and tsunami have cut off the plant's electrical power, and that backup generators have been disabled by the tsunami.
- Another aftershock hits the west coast of Honshu - 6.3 magnitude. (5:56am)
- The Japanese Nuclear and Industrial Safety Agency announces that radiation near the plant's main gate is more than eight times the normal level.
- Cooling systems at three of the four units at the Fukushima Daini plant fail prompting state of emergency declarations there.
- At least six million homes - 10 percent of Japan's households - are without electricity, and a million are without water.
- The US Geological Survey says the quake appears to have moved Honshu, Japan's main island, by 8 feet and has shifted the earth on its axis.
- About 9,500 people - half the town's population - are reported to be unaccounted for in Minamisanriku on Japan's Pacific coast.
March 13, 2011 - People living within 10km (6.2 miles) of the Fukushima Daini and 20km of the Fukushima Daiichi power plants begin a government-ordered evacuation. The total evacuated so far is about 185,000.
- 50,000 Japan Self-Defense Forces personnel, 190 aircraft and 25 ships are deployed to help with rescue efforts.
- A government official says a partial meltdown may be occurring at the damaged Fukushima Daiichi plant, sparking fears of a widespread release of radioactive material. So far, three units there have experienced major problems in cooling radioactive material.
March 14, 2011 - The U.S. Geological Survey upgrades its measure of the earthquake to magnitude 9.0 from 8.9. The new reading means the quake is the fourth strongest earthquake since 1900.
- An explosion at the Daiichi plant No. 3 reactor causes a building's wall to collapse, injuring six. The 600 residents remaining within 30 kilometers of the plant, despite an earlier evacuation order, have been ordered to stay indoors.
- The No. 2 reactor at the Daiichi plant loses its cooling capabilities. Officials quickly work to pump seawater into the reactor, as they have been doing with two other reactors at the same plant, and the situation is resolved. Workers scramble to cool down fuel rods at two other reactors at the plant - No. 1 and No. 3.
- Rolling blackouts begin in parts of Tokyo and eight prefectures. Downtown Tokyo is not included. Up to 45 million people will be affected in the rolling outages, which are scheduled to last until April.
March 15, 2011 - The third explosion at the Daiichi plant in four days damages the suppression pool of reactor No. 2, similar to an explosion occurring at No. 1 over the weekend. Water continues to be injected into "pressure vessels" in order to cool down radioactive material.
March 16, 2011 - The nuclear safety agency investigates the cause of a white cloud of smoke rising above the Fukushima Daiichi plant. Plans are canceled to use helicopters to pour water onto fuel rods that may have burned after a fire there, causing a spike in radiation levels. The plume is later found to have been vapor from a spent-fuel storage pool.
- In a rare address, Emperor Akihito tells the nation to not give up hope, that "we need to understand and help each other." A televised address by a sitting emperor is an extraordinarily rare event in Japan, usually reserved for times of extreme crisis or war.
- After hydrogen explosions occur in three of the plant's reactors (1,2, and 3), Chief Cabinet Secretary Yukio Edano says radiation levels "do not pose a direct threat to the human body" between 12 to 18 miles (20 to 30 kilometers) from the plant.
March 17, 2011 - Gregory Jaczko, head of the Nuclear Regulatory Commission, tells U.S. Congress spent fuel rods in the No. 4 reactor have been exposed because there "is no water in the spent fuel pool," resulting in the emission of "extremely high" levels of radiation.
- Helicopters operated by Japan's Self-Defense Forces begin dumping tons of seawater from the Pacific Ocean on to the No.3 reactor to reduce overheating.
- Radiation levels hit 20 millisieverts per hour at an annex building where workers have been trying to re-establish electrical power, "the highest registered (at that building) so far," (TEPCO)
March 18, 2011 - Japan's Nuclear and Industrial Safety Agency raises the threat level from four to five, putting it on a par with the 1979 Three Mile Island accident in Pennsylvania. The International Nuclear Events Scale says a Level Five incident means there is a likelihood of a release of radioactive material, several deaths from radiation and severe damage to the reactor core.
April 12, 2011 - Japan's nuclear agency raises the Fukushima Daiichi crisis from Level 5 to a Level 7 event, the highest level, signifying a "major accident". It is now on par with the 1986 Chernobyl disaster in the former Soviet Union, which amounts to a "major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures."
June 6, 2011 - Japan's Nuclear Emergency Response Headquarters reports that reactors 1, 2 and 3 at the Fukushima Daiichi nuclear power plant experienced a full meltdown.
June 30, 2011 - The Japanese government recommends more evacuations of households 50 to 60 km northwest of the Fukushima Daiichi power plant. The government said higher radiation is monitored sporadically in this area.
July 16, 2011 - Kansai Electric announces that a reactor at the Ohi nuclear plant will be shut down due to problems with an emergency cooling system. This leaves only 18 of Japan's 54 nuclear plants producing electricity.
October 31, 2011 - In response to questions about the safety of decontaminated water, Japanese government official Yasuhiro Sonoda drinks a glass of decontaminated water taken from a puddle at the Fukushima Daiichi nuclear plant.
November 2, 2011 - Kyushu Electric Power Co. announces that it restarted No. 4 reactor, the first to come back online since the March 11 disaster, at the Genkai nuclear power plant in western Japan.
November 17, 2011 - Japanese authorities announce that they have halted the shipment of rice from some farms northwest of the Fukushima Daiichi nuclear power plant after finding higher-than-allowed levels of radioactive cesium.
December 5, 2011 - Tokyo Electric Power Company announces that at least 45 metric tons of radioactive water have leaked from the Fukushima Daiichi nuclear facility, and may have reached the Pacific Ocean.
December 16, 2011 - Japan's Prime Minister says that a "cold shutdown" has been achieved at the Fukushima Daiichi nuclear power plant, a symbolic milestone that means the plant's crippled reactors have stayed at temperatures below the boiling point for some time.
December 26, 2011 - Investigators report that poorly trained operators at the Fukushima Daiichi nuclear power plant misread a key backup system and waited too long to start pumping water into the units, according to an interim report from the government committee probing the nuclear accident.
February 27, 2012 - Rebuild Japan Initiative Foundation, an independent fact-finding committee, releases a report claiming that the Japanese government feared the nuclear disaster could lead to an evacuation of Tokyo while at the same time hiding its most alarming assessments of the nuclear disaster from the public as well as the United States.
May 24, 2012 - TEPCO (Tokyo Electric Power Co.) estimates about 900,000 terabecquerels of radioactive materials were released between March 12 and March 31 in 2011, more radiation than previously estimated.
June 11, 2012 - 1,324 Fukushima residents lodge a criminal complaint with the Fukushima prosecutor's office, naming Tsunehisa Katsumata, the chairman of Tokyo Electric Power Co. (TEPCO) and 32 others responsible for causing the nuclear disaster that followed the March 11 earthquake and tsunami and exposing the people of Fukushima to radiation.
June 16, 2012 - Despite public objections, the Japanese government approves restarting two nuclear reactors at the Kansai Electric Power Company in Ohi in Fukui prefecture, the first reactors scheduled to resume since all nuclear reactors were shut down in May 2012.
July 1, 2012 - Kansai Electric Power Co. Ltd. (KEPCO) restarts the Ohi nuclear plant's No. 3 reactor, resuming nuclear power production in Japan for the first time in the wake of the Fukushima Daiichi meltdown following the tsunami.
July 5, 2012 - The Fukushima Nuclear Accident Independent Investigation Commission's report finds that the Fukushima Daiichi nuclear crisis was a "man-made disaster" that unfolded as a result of collusion between the facility's operator, regulators and the government. The report also attributes the failings at the plant before and after March 11 specifically to Japanese culture. http://warp.da.ndl.go.jp/info:ndljp/pid/3856371/naiic.go.jp/en/
July 23, 2012 - A Japanese government report is released criticizing TEPCO. The report says that the measures taken by TEPCO to prepare for disasters were "insufficient," and the response to the crisis "inadequate."
October 12, 2012 - TEPCO acknowledges in a report that it played down safety risks at the Fukushima Daiichi power plant out of fear that additional measures would lead to a plant shutdown and further fuel public anxiety and anti-nuclear movements.
July 2013 - TEPCO admits that radioactive groundwater is leaking into the Pacific Ocean from the Fukushima Daiichi site, bypassing an underground barrier built to seal in the water.
August 28, 2013 - Japan's nuclear watchdog Nuclear Regulation Authority (NRA) says a toxic water leak at the tsunami-damaged Fukushima Daiichi power plant has been classified as a level 3 "serious incident" on an eight-point International Nuclear Event Scale (lINES) scale.
September 15, 2013 - Japan's only operating nuclear reactor is shut down for maintenance. All 50 of the country's reactors are now offline. The government hasn't said when or if any of them will come back on.
November 18, 2013 - Tokyo Electric Power Co. (TEPCO) says that operators of the Fukushima nuclear plant have started removing 1,500 fuel rods from damaged reactor No. 4. It is considered a milestone in the estimated $50 billion cleanup operation.
February 20, 2014 - TEPCO says an estimated 100 metric tons of radioactive water has leaked from a holding tank at the Fukushima Daiichi Nuclear Power Plant.
Japan Tsunami Debris:
The Japanese government estimates that the tsunami swept about five million tons of debris offshore, but that 70 percent sank, leaving 1.5 million tons floating in the Pacific Ocean.
The debris is most likely not radioactive. It is no longer in a "debris field," but scattered across a large area of the North Pacific.