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Lake Natron is a salt lake located in northern Tanzania, close to the Kenyan border, in the eastern branch of the East African Rift. The lake is fed by the Southern Ewaso Ng'iro River and also by mineral-rich hot springs. It is quite shallow, less than three meters (10 feet) deep, and varies in width depending on its water level, which changes due to high levels of evaporation, leaving concentrations of salt and other minerals, notably sodium carbonate (natron).

The Aletsch Glacier is pictured at dusk in Fiesch, Switzerland, August 11, 2015. One of Europe's biggest glaciers, the Great Aletsch coils 23 km (14 miles) through the Swiss Alps – and yet this mighty river of ice could almost vanish in the lifetimes of people born today because of climate change. The glacier, 900 metres (2,950 feet) thick at one point, has retreated about 3 km (1.9 miles) since 1870 and that pace is quickening. (Photo by Denis Balibouse/Reuters)

With the humpback calving season drawing to a close, here’s a look at some of Rita Kluge’s distinctive marine photos from the south Pacific. The Sydney-based photographer fell in love with whales after witnessing southern rights from the New South Wales coastline as they travelled to and from their feeding grounds in the Antarctic. She has since been to Tonga, where humpbacks breed and calf in winter months, to photograph them in the water. (Photo by Rita Kluge/The Guardian)

Polar bears prepare to feast on the remains of a bowhead whale, harvested legally by whalers during their annual subsistence hunt, just outside the Inupiat village of Kaktovik, Alaska, USA, 10 September 2017. As climate change shrinks their natural habitat, polar bears are turning Kaktovik into their very own sanctuary city. (Photo by Jim Lo Scalzo/EPA/EFE)

Vogue Italia is hosting a series of shows in Milan exploring how the magazine seeks to engage with hot social and political issues and provoke debate through images by top photographers. The Photo Vogue festival in Milan is hosting three exhibitions. The first, Fashion and Politics in Vogue Italia, looks at the magazine’s ambition to be a catalyst for change – in subtle and playful ways. Here: David LaChapelle – October 2004. (Photo by David LaChapelle/The Guardian)

Ismail Mustafa, seen in 2007. “I was collecting mushrooms on the hill near here. I didn’t see the mine. There was a huge explosion. When I woke up I saw that both my legs were gone; I thought my life was over. My brother and another guy were with me. They made a stretcher from sticks and tied it together with clothing. It took two hours to get off the mountain. ‘My daughter has also been injured. She found a shell and brought it into the house and put it on the fire. She didn’t know what she was doing at the time – she was only three. She is blind and has lost an arm”. (Photo by Sean Sutton for the Mines Advisory Group/The Guardian)

Sеx worker Geraldine, wearing cat make-up, excitedly holds up a dress she is thinking of buying from a street vendor, so that her partner, sitting nearby to keep her company, can see it, as she waits for clients outside the Revolution subway station, in Mexico City, Saturday, March 13, 2021. According to Geraldine, 30, the pandemic has cut clients and increased risks to the sеx workers but has also brought out more assistance for them too, both from dedicated organizations such as the activist group Brigada Callejera or “The Street Brigade” and from individuals who have donated food or clothing. (Photo by Rebecca Blackwell/AP Photo)

Fighting Infections (single image) | Fighting Pandemic by Sudipto Das. “It’s exhausting. A tram conductor in Kolkata, India, wears protective clothing from head to toe even in the heat of a summer afternoon. This was when restrictions were easing after India’s first Covid-19 lockdown – public transport was running, but staff were advised to suit up like this. We’ve all grown used to saluting the efforts of healthcare workers, but plenty of other people in public-facing jobs have performed gruelling duties too to keep people safe”. (Photo by Sudipto Das/Wellcome Photography Prize 2021)