The 70 finalists in Smithsonian.com's 13th annual photography competition have been announced. The contest attracted more than 46,000 submissions from photographers in 168 countries and territories. The judges have chosen ten finalists in each of the seven categories: Natural World, The American Experience, Travel, People, Altered, Mobile, and Sustainable Travel.

You can help choose the winner of one of the awards. Readers are invited to vote for a special Readers' Choice Award. Polling will remain open until 21 March, and the Grand Prize, Readers' Choice, and seven category winners will be announced on 22 March. In this gallery, IBTimes UK publishes a selection of the finalists; see all 70 and vote for your favourite here.

Smithsonian Photo Contest
Sun Head by Geert Weggen. Location: Bispgården, Jämtland, Sweden. Category: Natural World. "My garden has many flowers, and everyday red squirrels come to visit. I am almost always ready to take some shots of these wonderful animals."Geert Weggen
Smithsonian Photo Contest
Trucker Chapel by Lauren Pond. Location: Lodi, Ohio, US. Category: The American Experience. Truck driver Ben Blackburn, 46, participates in a Bible study session at the Transport For Christ (TFC) mobile chapel. TFC chaplains helped Blackburn enrol in trucking school after he lost his job during the recent economic recession. Transport For Christ, an international trucker ministry, has placed 45 mobile chapels at truck stops across the United States. The chapels offer Bible study, worship services and counseling from volunteer chaplains. They also give drivers a break from the struggles and solitude of life on the road.Lauren Pond
Smithsonian Photo Contest
Catch the Sunset by Tuan Nguyen Manh. Location: Vietnam. Category: Travel.Tuan Nguyen Manh
Smithsonian Photo Contest
Mating Red-Eyed Tree Frogs by Jennifer Guyton. Location: Costa Rica. Category: Natural World. "A male red-eyed tree frog (Agalychnis callidryas) takes a cheeky nap atop a female while he waits for her to lay eggs. This position is called "amplexus," and it puts the male in position to externally fertilise the female's eggs as soon as she has laid them."Jennifer Guyton
Smithsonian Photo Contest
Red China by Jian Wang. Location: Beijing. Category: Mobile. "A lady in a red dress walks in front of a red wall."Jian Wang
Smithsonian Photo Contest
Catching Fish by Simone Sbaraglia. Location: Lake Kerkini, Greece. Category: Natural World. "This photograph was taken in January 2015 on Lake Kerkini, Greece. The Dalmatian pelicans that inhabit that area have grown accustomed to humans since fishermen have fed them for hundreds of years. Their presence helps maintain a balanced ecosystem."Simone Sbaraglia
Smithsonian Photo Contest
A Side of Tear Gas by Shadi Rahimi. Location: Hebron, Palestinian Territories. Category: Travel. "I was on assignment for AJ covering clashes that had broken out in Hebron between young Palestinians and Israeli soldiers. Young men were tossing rocks toward a guard tower using slingshots and their hands. Soldiers were responding by firing tear gas canisters. Several blocks away, in an intersection with a market, I came across this booth. I watched the three men calmly place gas masks across their faces and continue to await customers. The scene struck me as so absurd, and yet so much a part of life there, that I asked them to take their photo."Shadi Rahimi
Smithsonian Photo Contest
Wildebeest Leap by Ricardo Cisneros. Location: Maasai Mara National Reserve, Narok County, Kenya. Category: Sustainable Travel. "This photograph was taken during the annual wildebeest migration. The wildebeest population is strong and provides nourishment for all the ecosystem. To me, sustainable travel is about never leaving behind things that can harm or change a delicate environment. I am careful not to even leave a footprint in a delicate dune. There are simple steps one can take when traveling abroad that can greatly reduce one’s footprint: Using as little water and electricity as possible; reducing waste by only bringing the essentials and reusing bottles and equipment; buying and eating locally and organically; never buying products that come from or support the hunt of endangered species, and never disturbing the natural behaviour of the wildlife."Ricardo Cisneros
Smithsonian Photo Contest
Spider Man by Adam Wong. Location: Nice, France. Category: Travel. "This was taken during a festival parade. A little Spider Man was not afraid of the monster."Adam Wong.
Smithsonian Photo Contest
Under Pressure by Adam Taylor. Location: Juneau Alaska. Category: Sustainable Travel. "This image was created underneath the Mendenhall Glacier. The beauty of these glaciers astounds me to this day, but as we all know, they are disappearing worldwide. The image has the ability to educate the world and give hope. Hope that with the right mindset, we can preserve the beauty that surrounds us by living sustainably. This will ensure that future generations can enjoy the same beautiful images we capture through such photographs. The inspiration for this photo came from seeing this glacier every day in my backyard. I attended university in Juneau, Alaska and from the campus you can catch glimpses of the glacier on a clear day. I felt personally connected to this body of ice, and as it began to recede before my very eyes, I knew I needed to preserved the beauty of it through images. I began to photograph it in late 2011 and am still photographing it today. This is because although I know we in Juneau can see the effects of climate change and know the importance in traveling and living sustainably, I feel it is important to document this change so that the world may understand the beauty we are losing every day."Adam Taylor
Smithsonian Photo Contest
I Voted, #FeesMustFall by Andreas Georghiou. Location: Pretoria, South Africa. Category: People. "The picture depicts a student from the University of Kwazulu-Natal, named Mandla Mbuyisa, who took part in the #FeesMustFall protest at the Union Buildings in Pretoria, South Africa on 23 October 2015. This protest came about in response to South Africa universities announcing a massive tuition fee increase for 2016. As many students in South Africa are poverty-stricken, they cannot afford to pay any more for tertiary education. What's more, the ruling government in South Africa promised free education for all before it came into power. The student in this photo is showing a "proof of voting" stamp in his identity document while being held back by a riot police barricade. The message he is trying to send to the government through this gesture is: 'I voted you into power, so give me the opportunity to be educated.'"Andreas Georghiou
Smithsonian Photo Contest
Ghost in the Woods by Benjamin Waller. Location: North Leigh, West Oxfordshire, United Kingdom. Category: Altered Images. "A fallow deer stands in an evergreen forest in North Leigh, West Oxfordshire."Benjamin Waller
Smithsonian Photo Contest
Chiberia by Cocu Liu. Location: Chicago, Illinois, US. Category: Mobile.Cocu Liu
Smithsonian Photo Contest
Women's Compartment of a Suburban Train by Tamina­Florentine Zuch. Location: Mumbai, India. Category: Travel. "Every day 7.5 million people make use of the suburban trains in Mumbai. Therefore, it is the biggest suburban network of the world. Almost every train has separate compartments for women to avoid sexual abuse."Tamina­Florentine Zuch
Smithsonian Photo Contest
My Time by Tihomir Trichkov. Location: Likoni, Mombasa, Kenya. Category: Sustainable Travel. "In February and March of 2014, I took a month off and went to work as a photographer/videographer in an orphan school in Likoni, one of the poorest neighbourhoods in Mombasa, Kenya. My videos and pictures helped raise money to finish the building of the school for 150 children and a sleeping building for 30 orphan kids. This is the school director's daughter on her break, while at school."Tihomir Trichkov