Two container ships collide in the Suez Canal on Monday. YouTube hide caption

Images from August 2000 (left) and August 2014 (right) show the drop in water levels in the Aral Sea. NASA hide caption

Security personnel guard the entrance of a road leading to a trail on Mount Ontake in Nagano prefecture Tuesday, three days after the volcano erupted in central Japan. Jiji Press/AFP/Getty Images hide caption

Pro-democracy activists sleep, rest and walk on a street near the government headquarters Tuesday in Hong Kong. Students and activists, many of whom have been camped out since late Friday, spent a peaceful night singing as they blocked streets in Hong Kong in an unprecedented show of civil disobedience to push demands for genuine democratic reforms. Wong Maye-E/AP hide caption

People check their phones at a pro-democracy demonstration in Hong Kong on Monday. Alex Ogle/AFP/Getty Images hide caption

Protesters take pictures with their mobile phones on Monday as they block the main street to the financial Central district, outside the government headquarters in Hong Kong. Carlos Barria/Reuters/Landov hide caption

A photo taken from a Kyodo News helicopter shows Japan's Self-Defense Forces personnel rescuing climbers who were in critical condition near the top of Mt. Ontake Monday, before rescue operations were suspended. Kyodo /Landov hide caption

Protesters march as they block the main street to the financial Central district, outside the government headquarters in Hong Kong, on Monday. Protesters at times numbering in the tens of thousands have gathered to demand the right to choose the territory's next leaders. Carlos Barria/Reuters/Landov hide caption