The Observer's 20 photographs of the week

The best images this week featured the environment and the weather. Here, the Niagara Falls are partially frozen due to extreme cold weather. The US experienced historic low temperatures due to the polar vortex descending from the Arctic Photograph: Aaron Harris/Reuters

Sinabung mount spews ash into the air during an eruption near Karo, North Sumatra. The erupting Indonesian volcano has forced further evacuations with more than 20,000 people now displaced Photograph: Sutanta Aditya/AFP

Photographer Ulet Ifansasti produced excellent work from the effects of the pyroclastic smoke spewing from Mount Sinabung. Here, people watch the eruptions from the district of Simpang Empat, North Sumatra Photograph: Ulet Ifansasti/Getty

And here, houses in Sigarang Garang are covered with ash from the Mount Sinabung eruptions Photograph: Ulet Ifansasti/Getty

Syrian men hold up a baby rescued from rubble caused by what activists say was an airstrike by forces loyal to Syrian President Bashar al-Assad in the Duma neighbourhood of Damascus Photograph: Bassam Khabieh/Reuters

A helicopter assists in fighting a forest fire in the rural town of Melipilla, Chile. According to local authorities, more than 17,000 hectares have been burned due to multiple fires Photograph: Ivan Alvarado/Reuters

And here people look at another extensive forest fire; this time in Angol, Chile Photograph: Camilo Tapia/EPA

In a photograph by regular Observer 20 gallery contributor, Yasuyoshi Chiba, people play football during sunset on Ipanema Beach in Rio de Janeiro, Brazil Photograph: Yasuyoshi Chiba/AFP

Children play with a man disguised as Batman at the Favela do Metro slum near the Maracana stadium in Rio de Janeiro, Brazil. Families living in the shantytown refuse to have their homes demolished as part of a project to renovate the district before the World Cup in June Photograph: Yasuyoshi Chiba/AFP

Cheryl Sealey, an independent adviser to Operation Trident, and Pastor Nims Obunge speak outside New Scotland Yard after a meeting with the Metropolitan Police following the Mark Duggan verdict. Duggan's family and supporters reacted with fury to the lawful killing verdict and vowed to continue fighting for justice for the father of six, whose death sparked nights of rioting across English cities in August 2011 Photograph: Ben Stansall/AFP

British singer Tulisa Contostavlos arrives at Southwark crown court. She was charged in connection with the supply of Class A drugs Photograph: Stefan Wermuth/Reuters

Japanese Macaque monkeys groom each other and relax in a hot spring at the Jigokudani, or Hell's Valley Monkey Park, in Yamanouchi, Nagano, Japan Photograph: The Asahi Shimbun/Getty

Supporters of ousted president Mohamed Morsi block a street during clashes with Egyptian security forces in Nasr City, Cairo. An Egyptian court adjourned the murder trial of deposed president Morsi citing 'weather conditions' that prevented him from being taken to court Photograph: Virginie Nguyen Hoang/AFP

Photographer Nichole Sobecki produced powerful work this week from South Sudan. Here, people receive aid in Minkammen which was flooded with fleeing civilians. It was reported that the rumble of heavy artillery fire could be heard in the distance Photograph: Nichole Sobecki/AFP

Civilians fleeing violence in the Bor region arrive at one of the many small ports in the Awerial region in another image by Nichole Sobecki. Thousands of exhausted civilians are crowding into the fishing village of Minkammen, South Sudan Photograph: Nichole Sobecki/AFP

And in this final photograph by Nichole Sobecki, a woman holds her child at a makeshift clinic for displaced people in a camp run by the United Nations in Juba Photograph: Nichole Sobecki/AFP

Portuguese rider Paulo Goncalves watches his motorbike burn at the Dakar Rally between Chilecito and Tucuman, Argentina Photograph: Franck Fife/AFP

Devotees take part in the procession of the Black Nazarene in Manila, Philippines. The Black Nazarene is a sculpture of Jesus and is believed to result in miracles Photograph: Ezra Acayan/NurPhoto/Rex

A worker walks past the breakthrough point of the world's first variable density tunnel boring machine in Kuala Lumpur. The machine is designed to dig through underground karstic limestone Photograph: Mohd Rasfan/AFP

A Kiev National Ballet dancer performs during a rehearsal of Tchaikovsky's Swan Lake at the Maestranza Theatre in Seville, Spain Photograph: Marcelo del Pozo/Reuters