The year 2019 saw an explosion of demonstrations across the world as people demanded an overhaul of entrenched political systems and action on climate change.Here is a look back at these and other events that marked the year.Protests sweep Latin AmericaOn January 23, Venezuela's opposition chief Juan Guaido declares himself interim president, escalating a long-running political and economic crisis.He is recognised by more than 50 countries, including the United States. But the army backs President Nicolas Maduro and he remains in his post.Major demonstrations erupt in Haiti in mid-September, after fuel shortages, and demand the resignation of President Jovenel Moise. Violence claims more than 40 lives.A metro ticket hike in Chile's capital mid-October is the trigger for protests which claim more than 20 lives before a referendum on reforms is agreed.Bolivia is gripped by three weeks of demonstrations after President Evo Morales claims to win a fourth term on October 20. Dozens are killed. Morales resigns on November 10 and flees into exile as the government works on new elections.Ecuador is paralysed by nearly two weeks of protests in October and in Colombia strikes and demonstrations against the right-wing government begin mid-November.Boeing MAX groundedA March 10 Ethiopian Airlines crash leads to the global grounding of Boeing 737 MAX planes. It follows a Lion Air crash involving the same model six months earlier, with 346 lives lost in the two incidents.Boeing faces investigations and lawsuits, and is made to upgrade its systems, in a crisis that costs it billions of dollars.Brexit delayedBritain misses its March 29 deadline for leaving the European Union, as another year of Brexit turmoil leads Prime Minister Theresa May to quit on June 7.Her successor Boris Johnson is forced to ask the EU to again push back the deadline, now the end of January, and calls elections on December 12 in a bid to break the deadlock.First black hole photoOn April 10, astronomers unveil the first photo of a black hole, a phenomenon they were convinced existed even if it had never been seen before.Drawn from mountains of data captured two years earlier by telescopes across the world, it shows a super massive black hole 50 million light years away.This black hole resides 55 million light-years from Earth and has a mass 6.5-billion times that of the Sun. (Event Horizon Telescope collaboration et al.). Notre Dame burnsOn April 15, flames destroy the spire and roof of Paris's beloved Notre Dame cathedral but firefighters manage to save the gothic building, while many of its arts, relics and other treasures are rescued.Amid a global outpouring of emotion, $1.1bn is pledged for its reconstruction.Hong Kong eruptsOn June 9, anger in Hong Kong over a bill that would allow extradition to China erupts into violence for the first time. Over the next weeks pro-democracy protests harden into major street battles in the former British colony that returned to Chinese rule in 1997.China reacts furiously on November 28 when US President Donald Trump signs a law supporting the protesters.Turkey moves in SyriaOn October 9, Turkey launches an offensive into northern Syria to push back from the border Kurdish fighters it considers "terrorists".Two days earlier Trump had announced the withdrawal of US troops in the area, leading to charges that Washington had abandoned Kurdish allies who were vital in the battle against Islamic State (IS) jihadists.Turkey halts its operation on October 23 after the United States and Russia agree in separate deals to ensure the fighters leave the border region.The scene of clashes in northern Syria (Getty Images).IS leader killedOn October 27, Trump announces that IS leader Abu Bakr al-Baghdadi was killed in a US special forces raid in Syria, blowing himself up as he was pursued.After a five-year offensive to seize territory in Iraq and Syria, the jihadists were driven out of their last bastion in March by Kurdish-led forces.