Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello TPX IMAGES OF THE DAY

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Mount Etna, Europe's highest and most active volcano, erupts and lights up the sky in Sicily, Italy July 27, 2019. Picture taken July 27, 2019. REUTERS/Antonio Parrinello

Fresh shoe prints are seen at a migrant crossing spot on the Rio Grande near Mission, Texas, U.S., July 25, 2019. Picture taken July 25, 2019. REUTERS/Loren Elliott

A dry pond is pictured in a village of Menhai county in Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China, July 12, 2019. Picture taken July 12, 2019. REUTERS/Aly Song

A view of Monument Valley in Utah, US, June 27, 2019. Picture taken June 27, 2019. REUTERS/Pamela J. Peters

A view of Horseshoe Bend near Page, Arizona, U.S. June 26, 2019. Picture taken June 26, 2019. REUTERS/Pamela J. Peters

A view of Lower Antelope Canyon near Page, Arizona, U.S. June 26, 2019. Picture taken June 26, 2019. REUTERS/Pamela J. Peters

People hike on the Bright Angel Trail in the Grand Canyon near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

The Grand Canyon is seen from the South Rim near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

A person hikes on the Bright Angel Trail in the Grand Canyon near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

The Grand Canyon is seen from the South Rim near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

The Grand Canyon is seen from the South Rim near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

The Grand Canyon is seen from the South Rim near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

People hike on the Bright Angel Trail in the Grand Canyon near Grand Canyon Village, Arizona, U.S., February 22, 2018. REUTERS/Stephanie Keith

The Grand Canyon is seen from the South Rim near Grand Canyon Village, Arizona, U.S., February 22, 2018. Picture taken February 22, 2018. REUTERS/Stephanie Keith

The so-called "Mushroom Rock", formed by years of weathering and erosion, is seen on a cliff top outside Gharb, on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

Tourists walk near eroded limestone rock formations at Dwejra outside the village of San Lawrenz on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

Eroded limestone rock formations are seen at Dwejra outside the village of San Lawrenz on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

Fossils are seem in the rocks at Dwejra outside the village of San Lawrenz on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

Fossils of sea shells are seen in the weathered and eroded limestone cliffs outside Gharb, on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

Fossils of sea shells are seen in the rocks on a cliff top outside Gharb, on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

A tourist hikes past the so-called "Mushroom Rock", formed by years of weathering and erosion, on a cliff top outside Gharb, on the island of Gozo, Malta, January 25, 2018. REUTERS/Darrin Zammit Lupi

The logo of Russian state firm Rosgeologiya (RusGeology) is seen on a board at the St. Petersburg International Economic Forum 2017 (SPIEF 2017) in St. Petersburg, Russia, June 1, 2017. Picture taken June 1, 2017. REUTERS/Sergei Karpukhin

A river system flows near a small dam in outback Queensland near the town of Mount Isa, Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

Sand dunes can be seen near a salt lake containing small pans with water in outback Australia, May 9, 2016. Picture taken May 9, 2016. REUTERS/David Gray

A large river system can be seen in the tropical northern region located west of Darwin in Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

Dried-up rivers and creeks can be seen in outback Queensland near the town of Mount Isa, Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

A river system flows through outback Queensland near the town of Mount Isa in Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

A large lake can be seen amongst sand dunes in outback Queensland near the town of Mount Isa in Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

A cloud floats above a river system in outback Queensland near the town of Mount Isa in Australia, February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

River systems can be seen flowing near sand dunes in outback Queensland, Australia February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

River systems can be seen flowing near sand dunes in outback Queensland, Australia February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

Small dams situated next to a dirt road can be seen next to a river in outback Queensland, Australia February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

Small dams and a dried-up lake can be seen next to a dirt road in outback Queensland, Australia February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray TPX IMAGES OF THE DAY

River systems can be seen flowing near sand dunes in outback Queensland, Australia February 12, 2017. Picture taken February 12, 2017. REUTERS/David Gray

An aerial view shows an expanse of inhabited land in northern South Sudan, February 6, 2017. REUTERS/Siegfried Modola SEARCH "FAMILY MODOLA" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES.

Salt pans and dams are scattered across drought effected farmland in South Australia, November 12, 2015. A pioneering Australian scheme to improve the management of water in the world's driest inhabited continent is facing its first real test as an intensifying El Nino threatens crops and builds tensions between farmers and environmentalists. An El Nino, a warming of sea-surface temperatures in the Pacific, is already causing drought and other extreme weather, affecting millions of people across parts of the world, and experts warn that the intensifying weather pattern could emerge as one of the strongest on record. REUTERS/David Gray TPX IMAGES OF THE DAY

Ash spews from Mount Sinabung volcano during eruption as seen from Beras Tepu Village in Karo Regency, North Sumatra province, Indonesia June 29, 2015. More than 10,000 people from 12 villages, who are living around the slopes of Mount Sinabung, left their homes and moved to refugee camps, local media reported. REUTERS/Beawiharta

Ash spews from Mount Sinabung volcano during eruption as seen from Beras Tepu Village in Karo Regency, North Sumatra province, Indonesia June 29, 2015. More than 10,000 people from 12 villages, who are living around the slopes of Mount Sinabung, left their homes and moved to refugee camps, local media reported. REUTERS/Beawiharta

Ash spews from Mount Sinabung volcano during eruption as seen from Beras Tepu village in Karo Regency, North Sumatra province, Indonesia June 29, 2015. More than 10,000 people from 12 villages, who are living around the slopes of Mount Sinabung, left their homes and moved to refugee camps, local media reported. REUTERS/Beawiharta TPX IMAGES OF THE DAY

Mount Sinabung volcano spews hot lava as seen from Jeraya Village in Karo Regency, North Sumatra province, Indonesia June 23, 2015. More than 10,000 people from 12 villages, who are living around the slopes of Mount Sinabung, left their homes and moved to refugee camps, local media reported. REUTERS/Beawiharta TPX IMAGES OF THE DAY

Ash spews from Mount Sinabung, as seen from Perteguhan village in Karo Regency, Indonesia's North Sumatra province, June 20, 2015. More than 10,000 people from 12 villages around the slopes of Mount Sinabung left their homes and moved to refugee camps, local media reported on Friday. REUTERS/Beawiharta

Ash spew from Mount Sinabung, as seen from Perteguhan Village in Karo Regency, Indonesia's North Sumatra province, June 18, 2015. REUTERS/Beawiharta TPX IMAGES OF THE DAY

A general view of Calbuco volcano spewing ash and smoke from Puerto Varas, April 30, 2015. Chilean volcano Calbuco, which erupted twice last week, began sending a new cloud of ash and gas high into the sky on Thursday. REUTERS/Ivan Alvarado

A general view of Calbuco volcano spewing ash and smoke near Puerto Varas, April 30, 2015. Chilean volcano Calbuco, which erupted twice last week, began sending a new cloud of ash and gas high into the sky on Thursday. REUTERS/Ivan Alvarado TPX IMAGES OF THE DAY

A general view of Calbuco volcano spewing ash and smoke near Alerce town April 28, 2015. REUTERS/Ivan Alvarado

Residents wearing surgical masks to protect themselves against ash from the Calbuco volcano, walk in Curarrehue town, in the vicinity of Pucon city April 27, 2015. Calbuco was quieter on Sunday after unexpectedly erupting last week and puffing out plumes of gray ash, but authorities said it could erupt again and worries about the environmental impact grew. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Cristobal Saavedra

A dead salmon lies on a shore of a river affected by the ashes from Calbuco Volcano near Ensenada town, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

A general view of a river affected by ashes from Calbuco Volcano near Ensenada town, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

A cat sits on a fence at a house near Ensenada town which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

Soldiers arrive to help near Ensenada town which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

A scarecrow is seen in a backyard of a house nearby Ensenada which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

Locals round up cows to be transported from Ensenada which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

Soldiers remove ashes from a house nearby Ensenada which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado

Horses are transported from Ensenada town which is covered with ashes from Calbuco Volcano, April 27, 2015. Massive cleanup efforts continue in Chile after volcano Calbuco erupted without warning last week. Calbuco has spewed 210 million tonnes of ashes in the immediate surroundings, according to the National Service of Geology and Mining, coating nearby towns and prompting the evacuation of more than 6,500 locals. REUTERS/Ivan Alvarado